EZE, NNENNA CHIZOBA REG. NO.: PG/M.Sc/09/50741 ... THESIS.pdfEZE, NNENNA CHIZOBA REG. NO.:...

EZE, NNENNA CHIZOBA

REG. NO.: PG/M.Sc/09/50741

Ogbonna Nkiru

Digitally Signed by: Content manager’s Name

DN : CN = Webmaster’s name

O= University of Nigeria, Nsukka

OU = Innovation Centre

FACULTY OF AGRICULTURE

DEPARTMENT OF SOIL SCIENCE

SOIL CHARACTERIZATION AND LAND SUITABILITY

EVALUATION OF ANUKA FARMLAND IN NSUKKA

LOCAL GOVERNMENT AREA OF ENUGU STATE,

SOIL CHARACTERIZATION AND LAND

SUITABILITY EVALUATION OF ANUKA

FARMLAND IN NSUKKA LOCAL GOVERNMENT

AREA OF ENUGU STATE, NIGERIA

BY

EZE, NNENNA CHIZOBA

REG. NO.: PG/M.Sc/09/50741


UNIVERSITY OF NIGERIA, NSUKKA

DECEMBER, 2014

SOIL CHARACTERIZATION AND LAND SUITABILITY EVALUATION

OF ANUKA FARMLAND IN NSUKKA LOCAL GOVERNMENT AREA

OF ENUGU STATE, NIGERIA

BY

EZE, NNENNA CHIZOBA

REG. NO.: PG/M.Sc/09/50741

B. AGRIC. TECH. (FUTO)

A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE

REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF

SCIENCE (M.Sc) IN SOIL SCIENCE (SOIL SURVEY, CLASSIFICATION

AND LAND USE MANAGEMENT)


UNIVERSITY OF NIGERIA, NSUKKA

DECEMBER, 2014

CERTIFICATION

Ms. Eze Nnenna Chizoba, a postgraduate student in the Department of Soil Science, with

registration number PG/M.Sc/09/50741, has satisfactorily completed the requirements for

research work for the degree of Master of Science (M.Sc) in the Department of Soil Science

(Soil Survey, Classification and Land Use Management). This work is original and has not been

submitted in part or in full to any other diploma or degree of this or any other University.

................................................... ...............................................

Prof. F.O.R. Akamigbo Dr. P.I. Ezeaku

(Supervisor) (Ag. Head of Department)

.......................................... ........................................

Date Date

............................................

External Examiner

..................................

Date

DEDICATION

I dedicate this work to all lovers of knowledge acquisition and to my beloved family members:

Mr. and Mrs. Francis Eze, Arinzechukwu, Ijeoma, Okwudilichukwu and Chinweikem; my

grandmother, Mrs. Doris Anioke and the Management of Maranatha Foundation Schools, Ngwo.

ACKNOWLEDGEMENT

I sincerely express my appreciation to all who in one way or the other contributed to the success

of this research study. Thank you.

My profound gratitude goes to my supervisor, Prof. F. O. R. Akamigbo, whose fatherly and

academic guidance and advices made me better than at my arrival. The good Lord reward you

and improve your state of health.

I am forever grateful to all members of the department (tutorial and non-tutorial), for your

individual assistance to me in the course of this study. The Lord replenish you greatly.

I appreciate my darling parents and every member of my family for their prayers, support and

understanding at moments I went off-course. The Lord grant your respective desires.

To all my mates while in study, I am very grateful. You were worthy companions during my

study. The Lord bless you. Finally, God I thank you for your love, grace and mercies that never

ceased.

N. C. Eze

B. Agric. Tech. (FUTO)

TABLE OF CONTENTS

Title page -------------------------------------------------------------------------------------------- i

Certification ----------------------------------------------------------------------------------------- ii

Dedication ------------------------------------------------------------------------------------------- iii

Acknowledgement --------------------------------------------------------------------------------- iv

Table of Contents ----------------------------------------------------------------------------------- v

List of Tables --------------------------------------------------------------------------------------- viii

List of Figures -------------------------------------------------------------------------------------- ix

List of Plates ---------------------------------------------------------------------------------------- x

Abstract --------------------------------------------------------------------------------------------- xi

Chapter One

INTRODUCTION --------------------------------------------------------------------------------- 1

Chapter Two

LITERATURE REVIEW ------------------------------------------------------------------------- 3

Soil Characterization and Classification -------------------------------------------------------- 3

Land Evaluation ------------------------------------------------------------------------------------ 4

Land Suitability Classification ------------------------------------------------------------------- 6

Crop Growth Requirements ---------------------------------------------------------------------- 7

Chapter Three

MATERIALS AND METHODS ----------------------------------------------------------------- 9

Study Site -------------------------------------------------------------------------------------------- 9

Field Study ------------------------------------------------------------------------------------------ 9

Soil Sampling --------------------------------------------------------------------------------------- 13

Laboratory Analysis ------------------------------------------------------------------------------- 13

Soil Classification --------------------------------------------------------------------------------- 15

Land Suitability Evaluation (LSE) -------------------------------------------------------------- 15

Chapter Four

RESULTS ------------------------------------------------------------------------------------------ 21

Morphological Characteristics ------------------------------------------------------------------ 21

Particle Size Distribution ------------------------------------------------------------------------ 29

Soil Chemical Properties ------------------------------------------------------------------------ 32

Classification of Soils --------------------------------------------------------------------------- 36

Suitability Classification ------------------------------------------------------------------------ 38

Major Limitations to Land Suitability -------------------------------------------------------- 46

Chapter Five

DISCUSSION ----------------------------------------------------------------------------------- 48

Soil Properties ----------------------------------------------------------------------------------- 48

Soil Suitability ---------------------------------------------------------------------------------- 51

Suitability Limitations for Crops ------------------------------------------------------------- 52

Chapter Six

CONCLUSION AND RECOMMENDATIONS ----------------------------------------------60

References ------------------------------------------------------------------------------------------ 63

List of Tables

Table 1: Factor Rating of Land Use Requirements for Maize ----------------------------------- 16

Table 2: Factor Rating of Land Use Requirement for Cassava --------------------------------- 17

Table 3: Land and Soil Requirements for Oil Palm (Modified from Sys, 1985) ------------- 18

Table 4: Soil and Climate Requirements for Yam Production (Adopted: FPDD, 1989) ---- 19

Table 5: Morphology and Environmental Observation at the Profile Sites ------------------- 22

Table 6: Particle Size Distribution for Anuka Soil Samples --------------------------------------- 30

Table 7: Particle Size Distribution of Auger Soils of Anuka Farmland ------------------------- 31

Table 8: Chemical Properties of Soils of the Study Area ------------------------------------------ 33

Table 9: Chemical Properties of Auger Soils of the Study Area --------------------------------- 34

Table 10: Extractable Micronutrient Contents of Anuka Soils ---------------------------------- 35

Table 11: Summarized Classification of Soils Studied -------------------------------------------- 37

Table 12: Suitability Class Scores of the Study Area for Cassava ----------------------------- 39

Table 13: Suitability Class Scores of the Study Area for Maize ------------------------------- 40

Table 14: Suitability Class Scores of the Study Area for Oil Palm ---------------------------- 41

Table 15: Suitability Class Scores of the Study Area for Yam --------------------------------- 42

Table 16: Aggregate Suitability Scores and Suitability Classification

of the Pedons Indicating Limitation Characteristics ------------------------------------ 45

Table 17: Land Use Recommendation for Agricultural Crops of Anuka ------------------ 62

List of Figures

Fig. 1: A map showing Anuka (Nsukka LGA, 1:5000) ----------------------------------------- 10

Fig. 2: Map of the Study Site (source: Google search, 20/4/2011) -------------------------- 11

Fig. 3: A topographic map showing the contours of the study

site (source: Google search, 20/4/2011) -------------------------------------------------- 12

Fig. 4: Suitability Map for Cassava Production -------------------------------------------------- 53

Fig. 5: Suitability Map for Maize Production ---------------------------------------------------- 55

Fig. 6: Suitability Map for Oil Palm Production ------------------------------------------------- 57

Fig. 7: Suitability Map for Yam Production ------------------------------------------------------ 59

List of Plates

Plate 1: Soil unit P01 profile (cassava field) ----------------------------------------------------- 23

Plate 2: Soil unit P02 profile (maize field) ------------------------------------------------------- 24

Plate 3: Soil unit P03 profile (maize field) ------------------------------------------------------- 25

Plate 4: Soil unit P04 profile (yam field) --------------------------------------------------------- 26

Plate 5: Soil unit P05 profile (oil palm field) ---------------------------------------------------- 27

Plate 6: Soil unit P06 profile (oil palm field) ---------------------------------------------------- 28

Abstract

The land at Anuka, Nsukka Local Government Area of Enugu State in Southeastern Nigeria,

under the sub-humid tropical climate was evaluated for maize (Zea mays), cassava (Manihot

esculenta), yam (Dioscorea spp.) and oil palm (Elaeis guineensis) cultivation. Data were

obtained by field study and laboratory analyses. Six pedons were dug and described: two pedons

each for maize and oil palm fields, and one each for yam and cassava fields. These pedons were

dug to represent sampling units. Auger samples were also purposefully collected from the

sampling units at depths 0 - 20cm and 20 - 40cm. This was to investigate the nutrient spread in

the area. Soil samples from the pedogenetic horizons of the pedons were collected after profile

description, processed and analyzed. The pedons were designated P01 = cassava field, P02 and

P03 = maize fields, P04 = yam field, and P05 and P06 = oil palm fields. The textural classes of

the soils included sandy clay loam, sandy loam, sandy clay, loam, clay loam and clay, but the

dominant textural class is sandy clay loam. The overall results showed that the soils are acidic;

the phosphorus content is generally low; organic matter ranged from 0.42 - 4.31 %, decreasing

down the profile depth and is medium (>2.0 %) for epipedons. Exchangeable bases are generally

low: low exchangeable Ca (<3.2 cmol kg-1

), low to medium exchangeable Mg (0.2 - 3.2 cmol kg-

1), very low exchangeable Na (<0.70 cmol kg

-1) and deficient exchangeable K (<2.0 cmol kg

-1).

Total nitrogen content is moderately low to very low (0.042 % < N < 0.196 %). The soils met the

criteria for classification as Typic Dystrustults (P01, P03, P04, P05 and P06) and Aquic

Argiustults (P02) (Soil Taxonomy), correlated to Acrisols (FAO/UNESCO). The results showed

that although climate and topography are optimum or near optimum, there was no current highly

suitable (S1) soil unit for maize, cassava and yam cultivation by both parametric and non-

parametric methods of suitability evaluation. However, soil units P01 and P02 showed actual and

potential S1 for oil palm production in the study area. None of the sampling units showed high

suitability for its current utilization type. The severe constraints to crop cultivation in the area are

generally low fertility for all soil units; wetness for soil unit P02 and adverse soil physical

characteristic for soil unit P04. Application of organic manure, use of balanced fertilizer and

drainage management practices are necessary for maximum productivity of Anuka soils for the

evaluated crops.

Chapter One

INTRODUCTION

It is important that the land that will be used for agricultural production should be used according

to its capacity for optimization and sustainability of soil productivity (Adeboye, 1994). This

becomes very vital at this time when precision farming is gaining wider acceptance and the

relevance is particularly more now in the developing world where the use to which a land is put

is very often not related to its capacity (Senjobi, 2001).

A major problem of agricultural development in Nigeria is poor knowledge and appraisal of

suitability of parcels of land for agricultural production. The result is poor farm management

practices, low yield and an unnecessary high cost of production (Aderonke and Gbadegesin,

2013). Land evaluation using a scientific procedure is essential to assess the potentials and

constraints of a given land parcel for agricultural purposes (Rossiter, 1996). The knowledge of

soil limitations arising from land evaluation reports aims at ameliorating such limitations before,

or during cropping period (Lin et al., 2005). Therefore, soil as a main medium for cultivation

needs to be assessed (surveyed / characterized) scientifically. The performance assessment is

based on matching qualities of different land units in specific area with the requirements of

actual or potential land utilization types. This assessment results in classification of lands as to

their suitability to produce specific crops or combination of crops (Ezeaku, 2011).

Soil suitability evaluation involves characterizing the soils in a given area for specific land use

type. The suitability of a given piece of land is its natural ability to support a specified land use

such as rain-fed agriculture, livestock production, forestry, etc. The main objective of land

evaluation is to predict the inherent capability of a land unit to support a specific land use for a

long period of time without deterioration. Ozcan (2006) observed that all lands can be used for

utmost purpose if sufficient inputs are supplied. In the tropics, many different soil types occur as

a result of combination of pedogenic factors such as climate, topography, parent materials and

soil forming processes. Every land use has specific biophysical requirements with respect to land

conditions, and in the matching process of land evaluation, these biophysical requirements are

compared with the relevant combination of soil characteristics (measureable attributes like slope

percentage, drainage, soil texture, base saturation, etc) of a land resource; which are related to

the agricultural use of the soil and more specifically to specific crop requirements and tolerance

(Fischer et al., 2008).

Anuka is an agrarian community. Its dwellers are mainly commercial farmers of both small scale

and large scale production of several staple crops such as cassava, yam, maize and tree crops like

oil palm among others. The soils have been under intensive cropping by inhabitants of the

community. Despite the high agricultural development potential of the soils, the soils have not

been classified taxonomically to make for easy transfer of knowledge carried out on similar soils

elsewhere. Due to lack of guidance, many farmers cultivate crops on soils that may not be

suitable for their cultivation. Thus, the main objective of this study was to evaluate the suitability

of the soils of Anuka farmland, for both arable and plantation crops. The specific objectives

included to:

a) characterize the soils of the farm land, and classify them according to USDA Soil

Taxonomy and FAO/UNESCO;

b) determine the crop nutrient spread in the farm; and

c) evaluate the sampling units according to their suitability for maize, yams, cassava and oil

palm production.

Chapter Two

LITERATURE REVIEW

Soil Characterization and Classification

The type of soil formed under a particular set of environment is a function of the parent material

and time. Soil physico-chemical properties and micronutrients vary in their contents from soil to

soil and from one parent material to the other. The soils of Nsukka in eastern Nigeria have

generally been derived from the residua (disintegrated rock materials) of either false-bedded

sandstone or upper-coal measures (Asadu, 1990), which give rise to sandy and clayey soils,

respectively (Akamigbo and Asadu, 1983). These soils are low in inherent fertility and are

subjected to high temperature and rainfall of high intensity (Asadu et al., 2010). Nigerian soils

derived from basic rocks have higher content of micronutrients than those derived from acid

rocks (Chude et al., 1993). It is not so much abundance or the total content of these micronutrient

elements as the availability that is crucial to plant growth, since micronutrients in most soils are

ordinarily insoluble and are not easily available to plants.

Soils are the bases for most development projects. In order to ensure that the soil is put to the

most appropriate and sustainable use, there is every need for characterization and classification

of the soil. Soil characterization, soil classification and soil mapping provide a powerful resource

for the benefit of mankind, especially in the area of food security and environmental

sustainability (Esu, 2004). According to Ajiboye and Ogunwale (2010), earlier studies conducted

on the soils of various regions of Nigeria and subsequent classifications were based majorly on

the soil parent materials at the higher category classes. Soil classification study is a major

building block for understanding the soil, classifying it and getting the best understanding of the

environment. It is categorizing soils on the basis of their characteristics.

The USDA Soil Taxonomy (Soil Survey Staff, 1975 & 1999) and the FAO-UNESCO Soil

Classification System (FAO, 2001) are the two most used classification systems in Nigeria (Esu,

1999). For instance, the soils of Ejiba (Ajiboye and Ogunwale, 2010) were classified according

to the USDA (Soil Survey Staff, 2003) and World Reference Base (WRB) for Soil Resources

(FAO, 2006) systems. The soils were mostly Alfisols and Lixisols, with respect to such criteria

as nature of the epipedon, diagnostic master horizon, the cation exchange capacity, percentage

base saturation, organic carbon content, soil drainage characteristics, soil temperature, moisture

regimes and soil colour. Esu and Akpan-Idiok (2010), characterized the morphological and

physico-chemical properties of alluvial soils and classified them according to the USDA Soil

Taxonomy System (Soil Survey Staff, 1999) and the FAO/UNESCO/ISRIC World Reference

Base for Soil Resources (WRB) Classification System (FAO, 2001). The soils met the

requirement as Entisols and Vertisols.

The mineralogical analyses carried out on the clay fractions from the horizons of Nsukka soil

series (Akamigbo and Igwe, 1990) showed that the dominant clay minerals are kaolinite and

quartz; and the classifications according to Soil Taxonomy and FAO/UNESCO Soil Legend are

Ultisols and either Acrisols or Nitisols. The characteristics of Nsukka soils include their sandy

loam textural class, considerably high sand and moderate clay fraction formed from false-bedded

sandstone (Orajaka, 1975) and acidic reaction, associated with low activity clays, highly

degraded and leached profiles; which Akamigbo and Asadu (1983) described as deeply

weathered soils mostly derived from the residua of sedimentary materials. The CEC of the soils

are generally low (Asadu, 1990) as well as low exchangeable bases in the soils. Akamigbo and

Asadu (1983) reported these intrinsic properties as dependent on the parent materials of the soils.

Land Evaluation

In farming, risk is minimized by matching the requirements of land use to land qualities, which is

the role of land evaluation. Land evaluation (FAO, 1976) identifies the most limiting land

qualities and provides a good basis for advising farmers for optimum production. Dent and

Young (1981) stated that land evaluation is a prediction process of land potential for various

alternative uses, and it is one important component in the process of land-use planning (FAO,

1976). Land evaluation is a process that matches the characteristics of land resources for certain

uses using a scientifically standardized technique. The results can be used as a guide by land

users and planners to identify alternative land uses.

The utilization of land resources in accordance to the optimum carrying capacity in the

agricultural development can only be done if the information about the suitability of the land is

available. Suryana et al. (2005) stated that one of the basic information needed for agricultural

development is the spatial data (maps) of land resource potential. According to Wahyunto et al.

(1994), to determine potential areas for optimal agricultural development, balanced and

sustainable land resource data are required through the evaluation of land suitability. An

evaluation of suitable landscape for food crop cultivation based on the value of landscape type is

needed for decision making, coordination, and control for researchers and farmers to minimize

cost (Azis et al., 2006).

Many systems of land evaluation have been developed. They include the Storie Index (Storie,

1933), Land Capability Classification (Klingebiel and Montgomery, 1961) and Land Suitability

Evaluation (FAO, 1976). The basic principle of land evaluation is the identification of the

characteristics of the soil in a given landscape, identification of the soil requirement for the land

utilization type of interest and matching the two to establish the extent to which they match.

Some Land Evaluation Systems use several approaches such as parameters multiplying system,

parameters totaling system and matching system between land quality and land characteristics

with crop requirements. For instance, the Storie Index uses parameters multiplying system, while

Land Suitability Evaluation matches land quality and land characteristics with crop requirements.

Obviously, land evaluation has provided the needed solution to the issue of making soil survey

information useful to farmers and other land users (Ogunkunle, 2005).

Land quality is the complex attributes of lands and contains one or more land characteristics.

Important land qualities in any land evaluation include topography, soil, and climate. These are

closely linked to plant requirements (Ritung et al., 2007). The most important soil characteristics

in land evaluation include drainage, texture, soil depth, nutrient retention (pH, cation exchange

capacity), alkalinity, erosion hazard, and flood/inundation. Soil attribute is important for the

overall performance of land and play a preponderant role in checking land quality, and has been

used extensively by several authors to monitor land degradation (Senjobi , 2007; Senjobi and

Ogunkunle, 2011).

Land Suitability Classification

Hakim et al. (1986) stated that land suitability classification is the process of assessment and

classification of land units according to their suitability for a particular use. Land suitability

could be assessed for present condition (Actual Land Suitability) or after improvement (Potential

Land Suitability). Agricultural land use has benefited significantly from the use of suitability

systems in recent years. These systems have jointly showed their capabilities in the evaluation

and assessment of suitable sites for a variety of crops.

However, poor knowledge of soil suitability for agricultural production constitutes a major

problem to land use. For sustainable crop production, reliable soil data are the most important

prerequisite for the design of appropriate land-use systems and soil management practices as

well as for a better understanding of the environment (Aderonke and Gbadegesin, 2013). Though

soil classification and mapping are necessary and very useful for general land use planning, what

is of utmost importance to the farmer is knowing how profitable it is to grow a particular crop or

series of crops on a given plot of land, and what amendments are necessary to optimize the

productivity of the soil for specific crops (Aderonke and Gbadegesin, 2013).

Aguilar and Ortiz (1992) used the FAO Framework, in combination with the parametric Riquier

index to define the suitability classes (S1, S2, S3, N1 and N2) for land capability. In a recent

study, (Udoh et al, 2011), the conventional (non-parametric) methods as well as the parametric

method were used to evaluate the suitability of the eight pedons for rice and cocoa cultivation in

soils developed from alluvial deposit; in which five land quality groups were used for the study

and only a member of each of the five land quality groups was used in the calculation, because of

the strong correlation among members of the same group (Ogunkunle, 1993). The five land

quality groups were climate (c), soil physical characteristic (s), wetness (w), fertility status (f)

and toxicity (t).

On the basis of soil parameters provided by Harmonized World Soil Database (HWSD), seven

key soil qualities important for crop production have been derived, namely: nutrient availability,

nutrient retention capacity, rooting conditions, oxygen availability to roots, excess salts,

toxicities, and workability. These soil qualities are related to the agricultural use of the soil and

more specifically to specific crop requirements and tolerances (Fischer et al., 2008). If these

characteristics fulfill all requirements, the land is classified as “highly suitable (S1);” if one or

more characteristics do not meet the requirements the land is classified as “moderately suitable

(S2), marginally suitable (S3) or not suitable (N),” with the following implications:

� Suitable = The crop can be cultivated without difficulty; no additional land improvement

techniques are needed.

� Slightly suitable = Yields will be marginal when the soil is not improved. Therefore,

additional techniques to improve the soil are needed, such as drainage and irrigation

techniques or terrace building techniques.

� Not suitable = Implementation causes problems without notable yields.

Crop Growth Requirements

Climate and water requirements for growing oil palms (Elaeis guineensis) restrict it to growing

in tropical soil orders such as Ultisols, Oxisols and Inceptisols. Nutrient requirements of oil

palms are higher than what can be sustained by any soil for economical yields. Macro-nutrient

requirements for nitrogen and potassium are especially high; and a high cation exchange capacity

(CEC) is an important requirement for soil where oil palms grow.

Land suitability evaluation for oil palm in heavy rainfall areas of Nigeria (Ogunkunle, 1993) are

known. Oil palms require a well-drained soil that also retains water well. A soil that forms a

variety of plentiful aggregates is good for growing oil palms. Sustainable plantation of palm oil

plants must grow on a naturally level area.

Cassava grows well under a wide range of soils but prefers porous, friable soils with some

organic matter content and depth of 30-40 cm. It will not survive extended waterlogged

conditions. Cassava prefers soils with pH between 6-7, and clay content less than 18 %. It does

not tolerate saline conditions. The limitations found in most soil suitability evaluation for cassava

production are poor soil structure and texture. This affects the aggregate and water-holding

capacity of the soil. Other constraints include drainage and soil fertility. Ande (2011) in his

study noted the properties of Apomu soil suitable for cassava production, essentially for its sandy

loamy texture, coupled with its gentle slope of 3-4 %. However, very little attention has been

given to the proper cultivation and soil requirement of the crop (Ande et al., 2008). This could be

attributed to the ease with which the crop grows and secondly because of its position usually as

the last crop in the traditional agricultural system before the land is left to fallow.

Although maize (Zea mays) is found to grow throughout Nigeria under a wide range of agro-

climatic conditions, three broad agro-ecological zones can be distinguished for maize production.

They are the forest, the moist (guinea) savanna and the forest/savanna transition zone. High

insolation, relative high rainfall amount, high radiation, long dry season which limits the

incidence of pests and diseases and low night temperature are favorable ecology for maize. The

major limitations for maize production are soil texture and structure, which directly affect water-

holding capacity, permeability of the soil and other physical properties. Other limiting factors are

drainage and soil fertility, measured by CEC, organic matter and total nitrogen content. Sys et al.

(1991), stated 16-24 cmol kg-1

CEC and 1.2-2.0 % organic matter as optimal for maize.

Nitrogen, phosphorus and potassium are the primary nutrients most commonly demanded by

yam (Dioscorea spp.) Yam can be grown in all tropical countries provided water is not a limiting

factor. Deep, fertile, friable, and well-drained soils are ideal for yam cultivation, and optimum

textural classification of loam sandy soils (Onyekwere et al., 2009) is required for unhindered

anchorage and bulking of roots and tubers and easy harvest. In Nigeria, it is grown in areas

where the annual rainfall exceeds 800mm in amount and four months in duration.

Critical level of 0.15 % total Nitrogen is required for sustainable Dioscorea production ; and 2.0

cmol kg-1

exchangeable K is recommended for soils of southeastern Nigeria (FPDD, 1989) for

yam production. The cation exchange capacity and base saturation ratings are respectively 16

cmol kg-1

and greater than 35 %. Chukwu et al. (2007) stated that major yam soils of

southeastern Nigeria are deficient in total N. However, the northwest of Enugu/Anambra States

axes bordered by alluvial parent material are medium in N, having total N ranging from 0.15 –

0.20 %. (Chukwu et al., 2007).

Chapter Three

MATERIALS AND METHODS

Study Site

The study was conducted at Anuka in Nsukka Local Government Area of Enugu State, a location

in Southeastern Nigeria. The area is located between 6053

1 and 6

055

1 North and 7

013

1 and 7

014

1

East. The location map is bordered by 6046

1 and 6

092

1 North and 7

004

1 and 7

046

1 East. The

general climate is sub-humid tropical, having distinct rainy season and dry season, with rainfall

bi-modally distributed with peaks in July and September. The mean annual minimum rainfall is

1200 mm while the mean annual maximum rainfall is 2000 mm spread between April to early

November (Asadu, 2002). The average minimum and maximum temperatures are about 22o

C

and 30o C, respectively.

Anuka is characterized by undulating topography, with a few gentle to steep slopes. The

elevation ranges from 225 m to 280 m above sea level as shown in Figure 3. The natural

vegetation consists mainly of secondary forest due to prolonged human intervention through

annual small scale farming methods. The soils of Nsukka are generally weathered and naturally

low in fertility, derived from deposits of false bedded sandstone (Jungerius, 1964). The soils

developed at Anuka are moderately deep, well drained, reddish brown and have water table

below the profile throughout the area. Farming is the major socio-economic activity in the area.

The farm area is a wide expanse of one square-mile, of which about eighty-five hectares is being

cultivated for various crop production. Arable crops are mostly cultivated, and are grown as

rainfed crops. Major crops grown are maize (Zea mays), cassava (Manihot esculenta), yam

(Dioscorea spp.) and pepper (Capsicum spp. ).

Field Study

The reconnaissance activities were done using selected footpaths that traversed the survey area.

Strategic points were tracked along the farm boundaries with the use of hand-held Garcin GPS.

The existing land utilization types were maize, cassava, yam and oil palm farms. Soil profile pits

were dug on each of these land utilization types to represent sampling units. The base maps are

shown in figures 1, 2 and 3.

Fig. 1: A map showing Anuka (Nsukka LGA, 1:5000) Fig. 1: A map showing Anuka (Nsukka LGA, 1:5000)

6046

1

700

41

6046

1

700

41

6092

1 6092

1

704

61

704

61

Fig. 2: Map of the Study Site (source: Google search, 20/4/2011).

060 55

1 06

0 55

1

07

0 13

1

07

0 14

1

07

0 13

1

07

0 14

1

060 53

1 06

0 53

1

Fig. 3: A topographic map showing the contours of the study site (source: Google search, 20/4/2011).

060 55

1 06

0 55

1

060 53

1 06

0 53

1

07

0 1

31

0

70

13

1

07

0 1

41

0

70

14

1

Soil sampling

1. Auger samples: Auger points were made across the field to cover a representative area

of the field at random but at purposeful intervals. The auger depths were 0-20 cm and 20-

40 cm. This was to investigate the nutrient spread in the area. The auger samples were

bulked to make composite samples of the sampling units.

2. Profile pits: Soil profile pits were sited based on the current land utilization types in the

farm. From reconnaissance, four (4) land utilization types were identified within the field

which were used as sampling units, thus: maize, cassava, yam and oil palm.

Six profile pits were dug for the study: two each for maize and oil palm fields, and one each for

cassava and yam fields, with respect to the size of field for the land utilization types. Soil

properties examined included colour, texture, consistence, drainage, effective soil depth,

presence or absence of concretions and presence or absence of mottles. The pits were described

according to the FAO guidelines (FAO, 1990); and soil samples were collected from each

horizon in the soil profile pits for laboratory analysis.

Laboratory Analysis

The laboratory analyses consisted of detailed routine analyses of the soil samples for required

plant nutrients. The parameters analyzed included:

i. Soil pH

ii. Organic carbon

iii. Cation exchange capacity

iv. Exchangeable acidity

v. Exchangeable sodium

vi. Exchangeable potassium

vii. Exchangeable calcium

viii. Exchangeable magnesium

ix. Total nitrogen

x. Available phosphorus

xi. Copper

xii. Zinc

xiii. Iron

xiv. Manganese

xv. Boron

xvi. Molybdenum

xvii. Particle size distribution

The particle size analysis of the soil samples was determined by Bouyoucos hydrometer method

(Gee and Bauder, 1986), using NaOH as the soil dispersing agent. Soil pH in KCl and H2O was

determined using glass electrode pH meter.

Organic carbon was determined by dichromate wet oxidation method (Nelson and Sommer,

1982). The organic matter percentage was obtained by multiplying with the factor 1.724. Total

Nitrogen was determined by Kjeldahl process (Bremner and Mulvaney, 1982), and available

phosphorus by Bray-2 extraction method (Page et al., 1982).

Exchangeable cation was determined by extracting the soil with 1N NH4OAC (Thomas, 1982);

exchangeable Na and K evaluated using flame photometer while exchangeable Ca and Mg were

determined by atomic absorption spectrophotometer. Exchangeable acidity was determined by

extracting the soil with 0.1N KCl solution and titrating the aliquot of the extract with 1N NaOH

(McClean, 1965). The summation of the exchangeable bases and acidity gave the effective cation

exchange capacity (ECEC) value. The percentage aluminum saturation was computed by

dividing the value of total exchangeable aluminum by the effective cation exchange capacity

value and multiplying the quotient by 100; and the percentage base saturation by dividing the

value of total exchangeable bases by the ECEC value and multiplying the quotient by100.

Molybdenum was analysed by spectrophotometric method as described by Aggarwal and Patel

(1998), while Manganese, Iron, Zinc, Boron and Copper were in accordance with AOAC

methods (1990).

Soil Classification

The pedons were classified based on USDA Soil Taxonomy (Soil Survey Staff, 2010) and

correlated with FAO/UNESCO legend (FAO, 2006). The Soil Taxonomy was based on the

properties of the soil as were found during the study. The chemical, physical and morphological

properties were used as criteria for the classification. Detailed taxonomic classification to the

subgroup level was done.

Land Suitability Evaluation (LSE)

The FAO framework for soil suitability classification was used for the study. The land suitability

was evaluated by taking into consideration the soil characteristics related to land qualities

affecting the land use types. The soil drainage conditions were rated using soil depth, mottle

pattern and colour during profile description and soil textural classes, as against percolation test.

The established crop requirements in terms of land characteristics are presented in Tables 1, 2, 3

and 4.

Table 1: Factor Rating of Land Use Requirements for Maize

Land Land Unit S1 S2 S3 N1

Qualities Characteristics 100-95 94-85 84-40 39-20

Climate (c)

Water Mean annual Mm 12500- 1800-1600 1600- <500

Availability Rainfall 1800 500

Temperature Mean annual 0C 32-18 18-16 16-14 <14

Regime Temperature

Wetness (w)

Oxygen Soil drainage Well Imperfectly Poorly Very

Availability Drained Drained Drained Poorly

Drained

Fertility (f)

Nutrient Organic % 2-1.2 1.2-0.8 0.8-0.4 <0.4

Availability matter (0-15 cm)

Avail. P mg/kg >25 6−25 <6 Any

pH 5.5-7.5 5.0-5.5 or

4.0-5.0

or <4.0 or

7.5-8.0 8.0-8.5 >8.5

Nutrient

retention

Base saturation

%

50-35

35-20

20-15

<15

Soil Physical Characteristics (s)

Water Soil texture SCL LS, SL C S

Retention

Capacity

Rooting Soil depth Cm >75 >50 >20 <20

Condition

Salinity (n) EC ms cm-1

0-4 4-6 6-8 >8

Topography (t) Slope % 0-4 4-8 8-16 >16

(Modified from Sys et al., 1991).

Key: C=clay, SL=sandy loam, LS=loamy sand, SCL=sandy clay loam, S=sand, EC=Electrical

conductivity

Table 2: Factor Rating of Land Use Requirement for Cassava

Land Land Unit S1 S2 S3 N1

Qualities Characteristics

100-95 94-85 84-40 39-20

Climate (c.)

Moisture Mean annual Mm 1500- 1100-900 900-500 <500

Availability Rainfall 1100

Temperature Mean annual 0C 18-30 >16 >12 any

Regime Temperature

Wetness (w)

Oxygen Soil drainage Well Moderate or Poorly Very

Availability Drained Imperfectly Drained poorly

Drained drained

Fertility (f)

Nutrient Total N % >0.2 0.1-0.2 <0.1 Any

Availability Avail. P mg/kg >25 6-25. <6 Any

Exch. K cmol/kg >6 3-6. <3 Any

pH 6.1-7.3 7.4-7.8 or >8.4 or

5.1-6.0 <4.0

Nutrient CEC cmol/kg >16 3-16. <3 Any

Retention Base saturation % >35 20-35 <20 Any


Water Soil texture L, SC, LS, SiCL S, SiC C

Retention CL

Rooting Soil depth cm >100 100-75 75-50 <50

Condition

Salinity (n) EC ms cm-1

0-4 4-6 6-8 >8

Topography (t) Slope % 0-5 5-12 12-20 >20

(Source: Sys et al., 1991).

Key: C=clay, CL=clay loam, L=loam, SiC=silty clay, LS=loamy sand, SiCL=silty clay loam,

S=sand, SC=sandy clay, EC=Electrical conductivity

Table 3: Land and Soil Requirements for Oil Palm (Modified from Sys, 1985)

Land Qualities 100 95 85 60 40 25

S11 S12 S2 S3 N1 N2

Climatic (C):

Annual rainfall (mm) >2000 1700-2000 1450-1700 1300-1450 1300-1250 <1250

Length of growing season (months) <1 1-2 2-3 3-4 3-4 <4

Mean annual temp. (0C) >25 22-25 20-22 18-20 16-18 <16

Relative humidity (%) >75 70-75 65-70 62-65 60-62 <60

Topography (t):

Slope (%) 0-4 4-8 8-16 16-30 >30 >30

Wetness (w):

Flooding Fo Fo F1 F2 F2 F3

Drainage somewhat mod. Well mod. Well Poor aeric Poor, Poor, very poor,

poorly drained drainable not drainable

Soil physical properties (s):

Texture CL, SCL, L CL, SCL, L SCL SCL-Lfs, Any C, Cs, any

Structure Blocky Blocky

Soil depth (cm) >125 >100 >75 >50 >55 <50

Fertility (f):

CEC (cmol/kg-1Clay) >16 Any <10 <10 <5 <5

Base saturation (%) >35 35-20 20-15 15-10 <10 <10

Organic matter (%C) (0-15cm) >1.5 0.8-1.5 <0.8 <0.5 <0.3 <0.2 Symbols used for soil texture, structure and flooding are defined as follows: Cs: structure clay; Cm: massive clay; SiCs: silty clay, blocky clay; SiCL: silty clay loam; CL:

clay loam; Si: silt; SiL: silty loam; SC: sandy clay; L: loam; SCL: sandy clay loam; Lfs: loamy fine stand; LS: loam sand; Lcs: loam coarse sand; Fs: fine sand ;S: sand; CS:

coarse sand. F0 = No flooding, F1 =1 – 2 flooding months in > 10 years, F2 = not more than 2 – 3 months in 5 years out of 10 years, F3 = 2 months almost every year, F4

= 2 – 3 months every year.

Table 4: Soil and Climate Requirements for Yam Production (Adopted: FPDD, 1989)

Land quality Land characteristics Suitability rating

Climate Mean annual rainfall >800 mm

Wetness Soil drainage well drained

Soil physical Soil texture loam sandy soil

Characteristics Soil depth Deep (>75cm)

Soil fertility Total N >0.15 %

Exchangeable K >2.0 cmol Kg-1

CEC >16 cmol Kg-1

Base saturation >35 %

The suitability of the six pedons for cassava, maize, yam and oil palm production was evaluated

both by the conventional (non- parametric) (FAO, 1976) and parametric methods (Ogunkunle,

1993; Udoh et al., 2006). For the non-parametric evaluation, pedons were first placed in

suitability classes by matching their characteristics with the established requirements. The

aggregate suitability classes were indicated by the most limiting characteristic(s) of the pedon.

Five levels of limitations were used: no limitation (0), slight limitation (1), moderate limitation

(2), severe limitation (3) and very severe limitation (4). One limitation level was attributed to

each land characteristic. The final (aggregate) suitability classes were determined by the number

and intensity of the limitation(s), and the most unfavorable quality determined the suitability

classification. Suitability classes S1, S2, S3 and N were established.

For the parametric method, each characteristic was rated and the index of productivity (IP) for

each pedon was calculated using Square root method equation:

IP = A x B/100 x C/100 x … x F/100

Where: A is the overall lowest characteristic rating and B, C…F are the lowest characteristic

ratings for each land quality group (Udoh et al., 2006).

Five land quality groups: climate (c), topography (t), soil physical properties (s), wetness (w) and

fertility (f) were used in this method of evaluation. Only one member in each group was used for

calculation purpose because there are usually strong correlations among members of the same

group (e.g. texture and structure in group ‘s’) (Ogunkunle, 1993).

For actual (current) productivity index, all the lowest characteristic ratings for each land quality

group were substituted into the index of productivity equation above. However, in the case of

potential productivity index, it was assumed that the corrective fertility measure would no longer

have fertility constraints. Therefore, other qualities except fertility (f) were used to calculate the

potential productivity index. Suitability classes S1, S2, S3 and N are equivalent to IP values of

100 – 75, 74 – 50, 49 – 25 and 24 – 0, respectively .

Chapter Four

RESULTS

Morphological Characteristics

Six profile pits were dug and described in the month of February, 2012. They were dug to

represent landscapes occupied by different crops: maize (at elevations of 256 m and 225 m),

cassava (at altitude of 256 m), yam (at altitude of 238 m) and oil palm (at elevations of 231 m

and 227 m above sea levels) farm lands. These different landscapes were considered as sampling

units. The dug profiles were designated P01 - cassava field, P02 and P03 - maize fields, P04 -

yam field, and P05 and P06 - oil palm fields.

The physiography of the study site is nearly level plain on 1-4 % slope gradient. Groundwater

was not encountered at any profile depth. The soil structure included strong to moderate medium

blocky (profiles designated P01, P02 and P03), weak coarse plate-like and weak fine blocky

(profiles P05 and P06, respectively), as well as structureless (P04).

The drainage condition of the soils studied was moderate to well drained. Except profile P02 on

the crest of maize field, there were no mottles within 100 cm depth of the profile pits. However,

profile P02 was characterized with distinct sharp rusty red mottles (5YR4/6) within 46-108 cm

depth. The surface and subsurface soils of profiles P01, P03, P04, P05 and P06 were of bright

colours (high chroma): 2.5YR4/6 and 10R

5/6; 5YR

3/4 and 2.5YR

4/6; 5YR

3/4 and 10R

4/6; 2.5YR

3/4

and 10R5/8; and 5YR

3/6 and 10R

4/6, respectively. Conversely, profile P02, in the upslope had low

chroma: 7.5YR3/3 and 2.5YR

6/1 for surface and subsurface, respectively. The outline of horizons

within the profiles varied from clear smooth to gradual or diffuse smooth boundaries (Table 5).

The dug profile pits in the study site are shown in plates 1, 2, 3, 4, 5 and 6.

Table 5: Morphology and Environmental Observation at the Profile Sites

Location Depth

(cm)

Colour

(moist)

Mot

tles

Struct

ure

Consi

stence

Inclusions Boun

dary

Physiography

P01 (surface)

(subsurface)

0-17

88-130

2.5YR4/6, rb

10R5/6, r

Nm 3,m,b d,vh Hmic Gs

cs

Level plain in an undulating landscape on a1% slope at elevation of 256m

above sea level. Groundwater not encountered at 130cm depth. Land

utilization at time of sampling was cassava farm.

P02(surface)

(subsurface)

0-20

72-108

7.5YR3/3, db

2.5YR6/1, rg

M 3,m,b m,vf

Mis Gs

gs

Nearly level on a slope of 2% at altitude of256m above sea level. Moist

grayish profile with distinct sharp rusty red mottles. No roots, and water

table not encountered at108cm. Land utilization - maize.

P03(surface)

(subsurface)

0-22

80-136

5YR3/4, drb

2.5YR4/6, rb

Nm 2,m,b

2,m,pl

d, sf hlic;vffr;tw Gs

ds

Nearly level plain in an undulating land on a slope of 3% and elevation of

225m above sea level. Slightly moist profile, with mainly stones.

Groundwater not encountered at136cm. Current land utilization was maize.

P04(surface)

(subsurface)

0-14

35-62

5YR3/4, drb

10R4/6, r

Nm S d, l lis;cmr Gs

ds

Shallow and stony profile gently sloping on a slope of 4% at elevation of

238m above sea level. Profile lie on a weak rocky bed within 62cm depth.

Water table not encountered at 84cm. Land utilization at time of sampling

was yam farm.

P05(surface)

(subsurface)

0-15

77-125

2.5YR3/4, rb

10R5/8, r

Nm 1,c,pl d, lvf mcc,mwrm gs

gs

Reddish soil profile with concretionary cementation bedrock within 77-

125cm, lying on an almost flat plain of 1% slope and elevation of 227m

above sea level. Groundwater not encountered at 125cm.Land utilization

was oil palm.

P06(surface)

(subsurface)

0-33

106-135

5YR3/6, drb

10R4/6, r

Nm 1,f,b d, lvf ss,mwrm

mc,mwrm

ds

ds

Nearly level plain on a slope of 2% and elevation of 231m above sea level.

Stony down the profile; no water-table encountered at 135cm; land

currently used for oil palm plantation.

Legend

Colour: r = red, rb = reddish brown, db = dark brown, rg = reddish gray, drb = dark reddish brown.

Mottles: Nm = no mottles, M = mottled.

Structure: 1 = weak, 2 = moderate, 3 = strong, m = medium, c = coarse, f = fine, s = structureless, b = blocky, pl = plate-like.

Consistence: dvh = dry, very hard, mvf = moist, very firm, dsf = dry, soft, friable, dl = dry, loose, dlvf = dry, loose, very friable.

Inclusions: Stones: hmic = hard moderate irregular concretionary, mis = moderate irregular stones, hlic = hard large irregular concretionary, lis = large irregular

stones, mcc = moderate concretionary cementation, ss = simple stones, mc = moderate concretionary.

Roots: vffr = very few fibrous roots, cmr = common medium roots, mwrm = many woody root mat.

Fauna: t = termite burrows, w = worm cast.

Boundary: gs = gradual smooth, cs = clear smooth, ds = diffuse smooth.

Plate 1: Soil unit P01 profile (cassava field)

17-40cm

40-61cm

61-88cm

88-130cm

0-17cm

Root

Plate 2: Soil unit P02 profile (maize field)

0-20cm

20-46cm

46-72cm

72-108cm

0-20cm

20-46cm

46-72cm

72-108cm

0-20cm

20-46cm

46-72cm

72-108cm

0-20cm

20-46cm

46-72cm

72-108cm

Plate 3: Soil unit P03 profile (maize field)

0-22cm

22-47cm

47-80cm

80-136cm

Plate 4: Soil unit P04 profile (yam field)

0-14cm

14-35cm

35-62cm

62-84cm

Stony layer

Plate 5: Soil unit P05 profile (oil palm field)

0-15cm

15-39cm

39-77cm

77-125cm

Root

Plate 6: Soil unit P06 profile (oil palm field)

0-33cm

33-62cm

62-85cm

85-106cm

106-135cm

Particle Size Distribution

The physical properties of the soils of the study site are shown in Tables 6 and 7. For all the

profiles, silt fraction varied from 133 to 293 g kg-1

with mean values of 233 g kg-1

and 164 g kg-1

in the surface and subsurface soils, respectively. Similarly, sand fraction ranged from 422 to 642

g kg-1

with mean values of 548 g kg-1

and 474 g kg-1

in topsoils and subsoils, respectively; and a

range of 145 to 425 g kg-1

for clay fraction, with mean values of 227 g kg-1

and 369 g kg-1

in the

surface and subsurface soils, respectively. The texture of the soils studied ranges from sandy

loam to sandy clay loam for the topsoil, and clay loam to clay for the subsoil. The soil auger

samples showed high sand fraction with a mean value of 493 g kg-1

; followed by clay fraction

with a mean value of 308 g kg-1

; and the least is silt fraction with a mean value of 197 g kg-1

.

This trend is similar to the results of subsoils but different from those of topsoils. Sand fraction >

clay fraction > silt fraction in the subsoils; while sand fraction > silt fraction > clay fraction in

the topsoils.

Table 6: Particle Size Distribution for Anuka Soil Samples

Profile

No.

Horizon

Depth

(cm)

Clay

Silt

Fine

sand

Coarse

sand

Total

sand

Silt/Clay

ratio

Texture

��----------------g kg-1

---------------��

P01 Ap 0-17 265 253 266 216 482 0.95 Sandy clay loam

Cassava AB 17-40 265 273 256 207 463 1.03 "

Bt1 40-61 345 193 286 176 462 0.56 "

Bt2 61-88 385 193 257 165 422 0.50 Clay loam

Bt3 88-130 425 173 277 225 502 0.41 Clay

P02 Ap 0-20 245 293 246 217 463 1.20 Loam

Maize Bt1 20-46 305 153 157 386 543 0.50 Sandy clay loam

Bt2 46-72 305 153 216 326 542 0.50 "

Bt3 72-108 365 173 207 255 462 0.47 Sandy clay

P03 Ap 0-22 185 293 316 207 523 1.58 Sandy loam

Maize Bt1 22-47 265 193 275 267 542 0.73 Sandy clay loam

Bt2 47-80 305 153 357 195 542 0.50 "

Bt3 80-136 405 153 305 137 442 0.38 Sandy clay/clay

P04 Ap 0-14 145 233 446 177 623 1.61 Sandy loam

Yam Bt1 14-35 205 173 477 145 622 0.84 Sandy clay loam/Sandy loam

Bt2 35-62 345 153 396 106 502 0.44 Gravelly sandy clay loam

P05 Ap 0-15 145 213 347 296 643 1.47 Sandy loam

Oil palm Bt1 15-39 265 153 337 246 583 0.58 Sandy clay loam

Bt2 39-77 365 153 280 205 482 0.42 Sandy clay

Bt3 77-125 405 133 256 207 463 0.33 "

P06 Ap 0-33 205 253 396 147 543 1.23 Sandy clay loam/sandy loam

Oil palm Bt1 33-62 325 193 416 66 482 0.59 Sandy clay loam

Bt2 62-85 365 153 377 105 482 0.42 Sandy clay

Bt3 85-106 425 153 326 96 422 0.36 Clay

Bt4 106-135 405 173 286 136 422 0.43 Clay

Range

145-

425

133-

293

422-

643

Mean

(Topsoil) 227 226 548

(Subsoil) 369 164 474

Table 7: Particle Size Distribution of Auger Soils of Anuka Farmland

Auger

No.

Depth

(cm)

Clay

Silt

Fine

sand

Coarse

sand

Total

sand

Silt/Clay

ratio

Texture

��------------------g kg-1

------------------��

A01 0-20 252 213 290 245 535 0.85 Sandy clay loam

20-40 332 193 259 217 475 0.58 “

A02 0-20 252 213 348 187 535 0.85 “

20-40 332 193 277 198 475 0.58 “

A03 0-20 332 193 310 165 475 0.58 “

20-40 492 153 230 125 355 0.31 Clay

A04 0-20 232 193 366 209 575 0.83 Sandy clay loam

A05 0-20 232 233 330 205 535 1.00 “

20-40 312 193 306 169 475 0.62 Sandy clay loam

Range

232-

492

153-

233

355-

575

Mean 308 197 493

Soil Chemical Properties

The chemical properties of the soils are given in Tables 8 and 9. The overall results show that the

soils are strongly to moderately acidic with pH (H2O) ranging from 4.6 to 6.0. The phosphorus

content ranged from 2.80 mg kg-1

to 43.84 mg kg-1

, with wide range for soils of P02 and P03.

Organic matter content of the soil ranged from 0.42 - 4.31 %, decreasing down the profile depth.

Exchangeable Ca is 0.2 - 3.2 cmol kg-1

, exchangeable Mg is 0.2 - 3.2 cmol kg-1

and

exchangeable Na is 0.10 - 0.39 cmol kg-1

. The soil exchangeable K content is less than 2.0 cmol

kg-1

, except for P02 and P03 Ap horizons, viz: 0.61 and 0.49 cmol kg-1

.

However, the exchangeable bases for soil unit P02 are higher than those of the other soil units:

Ca ranged from 0.2 - 3.2 cmol kg-1

, Na ranged from 0.10 - 0.39 cmol kg-1

, K ranged from 0.03 -

0.61 cmol kg-1

and Mg ranged from 0.2 - 3.2 cmol kg-1

. Total Nitrogen content is moderately low

(some less than 0.15 %).

Table 10 shows the extractable micronutrient distribution of the topsoils of Anuka farmland.

Exchangeable Mo, B, Cu, Fe, Zn and Mn ranged from 6.27 - 14.31 mg kg-1

, 3.56 - 5.94 mg kg-1

,

0.25 - 1.12mg kg-1

, 2.80 - 4.48 mg kg-1

, 1.4 - 6.4 mg kg-1

and 0.4 - 6.2 mg kg-1

, with a mean

value of 8.36 mg kg-1

, 4.53 mg kg-1

, 0.50 mg kg-1

, 3.82 mg kg-1

, 3.04 mg kg-1

and 2.45 mg kg-1

,

respectively.

Table 8: Chemical Properties of Soils of the Study Area

Profile No. Depth pH OM TN Avail. P Exchangeable bases Exch. Acidity CEC TEB ECEC BS % Al Sat.

Ca Na K Mg H+

Al3+

(cm) (H2O) (KCl) (%) (%) (mgkg-1

) �---------------------------- cmolkg-1

-------------------------------------�

(%)

P01 Ap 0-17 4.7 4.3 2.57 0.168 2.80 0.4 0.29 0.12 1.2 4.0 0.4 6.80 2.01 6.41 31.36 6.24

AB 17- 40 5.0 4.4 2.01 0.168 2.80 0.6 0.19 0.07 0.6 2.0 0.8 6.80 1.46 4.26 34.27 18.78

Bt1 40- 61 5.1 4.4 1.32 0.098 2.80 0.6 0.10 0.04 1.2 2.2 0.8 7.60 1.94 4.94 39.27 16.19

Bt2 61- 88 5.8 4.6 1.39 0.140 3.73 0.6 0.19 0.03 0.4 1.8 1.2 9.20 1.22 4.22 28.91 28.44

Bt3 88- 130 6.0 4.7 0.83 0.042 2.80 0.4 0.10 0.04 0.8 1.6 0.4 6.00 1.34 3.34 40.12 11.98

P02 Ap 0-20 5.3 5.0 4.31 0.126 43.84 3.2 0.39 0.61 1.8 1.0 Nil 9.60 6.0 7.0 85.71 Nil

Bt1 20- 46 5.1 4.2 1.81 0.196 2.80 1.0 0.29 0.14 1.4 5.6 3.2 11.20 2.83 11.63 24.33 27.52

Bt2 46- 72 5.1 4.6 0.97 0.126 2.80 0.8 0.29 0.14 2.2 4.8 3.4 12.80 3.43 11.63 29.49 29.23

Bt3 72- 108 5.6 4.6 0.42 0.196 3.73 0.8 0.10 0.14 3.2 5.0 2.8 12.80 4.24 12.04 35.22 23.26

P03 Ap 0- 22 5.7 4.8 3.82 0.168 31.71 1.8 0.39 0.49 1.0 1.6 Nil 8.40 3.68 5.28 69.70 Nil

Bt1 22- 47 4.6 4.3 2.22 0.140 3.73 1.0 0.29 0.10 0.6 1.6 1.2 8.00 1.99 4.79 41.54 25.05

Bt2 47- 80 5.2 4.5 1.60 0.098 3.73 0.6 0.19 0.10 0.6 2.0 0.6 5.20 1.49 4.09 36.43 14.67

Bt3 80- 136 5.6 4.8 1.25 0.196 2.80 0.8 0.10 0.04 1.0 2.0 0.4 6.00 1.94 4.34 44.70 9.22

P04 Ap 0- 14 5.2 4.5 2.85 0.168 11.19 0.6 0.19 0.12 1.0 2.0 0.6 6.00 1.91 4.51 42.35 13.30

Bt1 14- 35 5.1 4.7 1.95 0.126 3.73 0.4 0.29 0.10 0.2 1.6 0.4 5.20 0.99 2.99 33.11 13.38

Bt2 35- 62 5.2 4.5 1.39 0.098 2.80 0.6 0.10 0.07 0.6 1.4 Nil 4.40 1.37 2.77 49.46 Nil

P05 Ap 0- 15 5.1 4.4 3.27 0.168 3.73 0.6 0.19 0.06 0.6 2.6 1.2 9.20 1.45 5.25 27.62 22.86

Bt1 15- 39 5.6 4.4 2.43 0.126 3.73 0.6 0.19 0.08 2.2 2.2 1.2 7.20 3.07 6.47 47.45 18.55

Bt2 39- 77 5.7 4.4 1.11 0.098 3.73 0.6 0.19 0.05 0.2 1.8 0.8 6.80 1.04 3.64 28.57 21.98

Bt3 77- 125 5.8 4.6 1.32 0.154 3.73 0.2 0.10 0.05 1.6 2.0 0.6 6.80 1.95 4.55 42.86 13.19

P06 Ap 0- 33 5.1 4.3 1.81 0.196 3.73 0.6 0.29 0.08 0.2 2.6 1.2 7.20 1.17 4.97 23.54 24.15

Bt1 33- 62 5.3 4.5 1.04 0.098 2.80 0.6 0.19 0.10 0.2 2.2 1.6 6.40 1.09 4.89 22.29 32.72

Bt2 62- 85 5.5 4.5 1.11 0.154 3.73 0.4 0.19 0.06 0.8 2.6 1.2 7.60 1.45 5.25 27.62 22.86

Bt3 85-106 6.0 4.5 0.83 0.154 2.80 0.8 0.10 0.04 1.6 1.8 1.6 6.40 2.54 5.94 42.76 26.94

Bt4 106-135 5.9 4.5 0.56 0.098 2.80 1.2 0.29 0.04 0.6 2.0 1.0 6.80 2.13 5.13 41.52 19.49

OM= Organic Matter; TN= Total Nitrogen; CEC= Cation Exchange Capacity; TEB= Total Exchangeable Bases; ECEC= Effective Cation Exchange Capacity;

BS= Base Saturation; % Al Sat= Percentage Aluminum Saturation.

Table 9: Chemical Properties of Auger Soils of the Study Area

Auger Depth pH OM TN Avail. P Exchangeable bases Exch. Acidity CEC TEB ECEC BS % Al Sat.

points Ca Na K Mg H+

Al3+

(cm) (H2O) (KCl) (%) (%) (mgkg-1

) �------------------------------ cmolkg-1

-----------------------------� (%)

A01 0- 20 5.7 4.8 4.38 0.098 4.66 1.4 0.29 0.18 1.8 2.2 0.6 9.60 3.67 6.47 56.72 9.27

20- 40 5.8 4.7 2.85 0.154 3.73 0.8 0.29 0.07 0.8 2.0 1.4 8.80 1.96 5.36 36.57 26.12

A02 0- 20 5.8 4.6 3.06 0.112 20.52 1.4 0.29 0.44 0.4 2.2 0.6 6.40 2.53 5.33 47.47 11.26

20- 40 5.5 4.6 2.15 0.126 4.66 1.2 0.29 0.19 1.0 1.6 0.8 8.40 2.68 5.08 52.76 15.75

A03 0- 20 6.2 5.7 3.27 0.140 60.62 3.2 0.29 0.35 1.2 0.6 Nil 6.80 5.04 5.64 89.36 Nil

20- 40 6.0 5.0 1.95 0.126 11.19 0.8 0.29 0.20 2.2 1.6 Nil 6.40 3.49 5.09 68.57 Nil

A04 0- 20 5.7 4.5 3.27 0.154 9.33 0.6 0.29 0.11 1.2 1.2 1.8 7.20 2.20 5.20 42.31 34.62

A05 0- 20 5.9 4.9 3.40 0.112 5.60 1.2 0.29 0.10 1.8 2.4 0.8 6.00 3.39 6.59 51.44 12.14

20- 40 6.1 4.9 1.95 0.126 2.80 1.2 0.29 0.06 0.8 1.8 0.2 7.20 2.35 4.35 54.02 4.60

OM= Organic Matter; TN= Total Nitrogen; CEC= Cation Exchange Capacity; TEB= Total Exchangeable Bases; ECEC= Effective Cation Exchange Capacity;

BS= Base Saturation; % Al Sat= Percentage Aluminum Saturation

Table 10: Extractable Micronutrient Contents of Anuka Soils

Description/ Mo B Cu Fe Zn Mn

Depth(cm) �-----------------------------------------(mg kg-1

)---------------------------------------�

P01 (0- 17) 7.73 3.56 0.63 3.92 2.4 6.2

P02 (0- 20) 6.58 4.75 1.12 3.36 6.4 2.2

P03 (0- 22) 14.31 3.56 0.60 3.36 2.4 0.4

P04 (0- 14) 8.98 3.56 0.25 3.92 1.4 0.6

P05 (0- 15) 8.15 4.75 0.36 3.92 2.4 3.4

P06 (0- 33) 6.47 3.56 0.38 3.92 1.8 1.0

A01 (0- 20) 6.89 3.56 0.26 3.92 2.8 2.0

A02 (0- 20) 7.41 4.75 0.61 4.48 3.0 1.8

A03 (0- 20) 7.83 5.94 0.52 2.80 6.2 1.2

A04 (0- 20) 11.38 5.94 0.42 3.92 2.2 2.2

A05 (0- 20) 6.27 5.94 0.35 4.48 2.4 6.0

Range 6.27-14.31 3.56- 5.94 0.25- 1.12 2.80- 4.48 1.4- 6.4 0.4- 6.2

Mean 8.36 4.53 0.50 3.82 3.04 2.45

Legend: Mo=Molybdenum, B= Boron, Cu=Copper, Fe=Iron, Zn=Zinc, Mn=Manganese.

Classification of Soils

All pedons were mainly of kandic diagnostic horizon judging from their low activity clays

[CEC/% clay ratio <0.24(Brady and Weil, 1999)]; except that represented by P02 which has

argillic subsurface horizon of accumulated clay that has moved downward from the upper

horizon, bearing from its active cation exchange activity class (CEC/% clay ratio = 0.42). The

soils were formed in ustic moisture regime and have well developed B horizons. The CEC and

ECEC contents of the soils ranged from 6.0 - 12.8 cmol kg-1

and 2.77 - 12.04 cmol kg-1

,

respectively, with percentage base saturation less than 50 % in all the profiles, except the Ap

horizons of P02 and P03 (which were 85.71 % and 69.70 %, respectively). Hence, the soils were

classified as Ultisols. The taxonomic classification of the soils to the subgroup category are thus:

A. Order: Ultisols

Suborder: Ustults (sub-humid climate)

Great Group: Dystrustults (low base saturation)

Subgroup: Typic Dystrustults.

B. Order: Ultisols

Suborder: Ustults

Great Group: Argiustults (argillic horizon)

Subgroup: Aquic Argiustults (restricted drainage).

In the FAO/UNESCO, all the soils were correlated as Acrisols for their low base saturation. The

Soil Taxonomy (USDA) and the Soil Legend (FAO/UNESCO) Classifications for the studied

soils are summarized in Table 11.

Table 11: Summarized Classification of Soils Studied

Sampling unit Soil Taxonomy (USDA) Soil Legend (FAO/UNESCO)

P01 Typic Dystrustults Acrisols

P02 Aquic Argiustults Acrisols





Suitability Classification

The factor rating of land use requirements for maize, cassava, oil palm and yam (Tables 1,2,3

and 4) were matched with the properties of the studied soils. In tables 12, 13, 14 and 15 are the

individual scores (ratings) of the land characteristics and the aggregate suitability classes of the

soil units for the various crops.

Table 12: Suitability Class Scores of the Study Area for Cassava

P01 P02 P03 P04 P05 P06

Climate (c)

Annual rainfall S1 (95) S1 (95) S1 (95) S1 (95) S1 (95) S1 (95)

Mean annual temperature S1 (95) S1 (95) S1 (95) S1 (95) S1 (95) S1 (95)

Topography (t)

Slope S1 (100) S1 (100) S1 (100) S1 (95) S1 (100) S1 (100)

Wetness (w)

Soil drainage S1 (100) S3 (60) S2 (85) S1 (100) S1 (100) S1 (100)


Soil texture S1 (95) S1 (100) S1 (95) S2 (85) S1 (95) S1 (95)

Soil depth S1 (100) S1 (100) S1 (100) S3 (60) S1 (100) S1 (100)

Soil Fertility (f)

Total. N S2 (85) S2 (85) S2 (85) S2 (85) S2 (85) S2 (85)

Avail. P S3 (60) S3 (60) S3 (60) S3 (60) S3 (60) S3 (60)

Exch. K S3 (60) S3 (60) S3 (60) S3 (60) S3 (60) S3 (60)

pH S2 (85) S2 (85) S2 (85) S2 (85) S2 (85) S2 (85)

CEC S2 (85) S2 (85) S2 (85) S2 (85) S2 (85) S2 (85)

Base saturation S1 (95) S2 (85) S1 (100) S1 (95) S2 (85) S2 (85)

Aggregate Suitability:

Potential S1 (90) S3 (45) S1 (75) S3 (44) S1(90) S1 (90)

Actual (current) S2 (57) S3 (45) S2 (53) S3 (44) S2 (57) S2 (57)

Aggregate suitability scores: S1=100-75, S2=74-50, S3=49-25, N1=24-15,N2=14-0

Table 13: Suitability Class Scores of the Study Area for Maize

P01 P02 P03 P04 P05 P06

Climate (c)

Annual Rainfall S1 (95) S1 (95) S1 (95) S1 (95) S1 (95) S1 (950


Topography (t)

Slope S1 (100) S1 (100) S1 (95) S1 (95) S1 (100) S1 (100)

Wetness (w)





Soil Fertility (f)

O M S1 (100) S1 (100) S1 (100) S1 (100) S1 (100) S1 (95)

Avail. P S3 (60) S3 (60) S3 (60) S3 (60) S3 (60) S3 (60)

pH S2 (85) S2 (85) S2 (85) S2 (85) S2 (85) S2 (85)



Potential S1 (90) S3 (44) S2 (69) S1 (75) S1 (76) S1 (90)



Table 14: Suitability Class Scores of the Study Area for Oil Palm

P01 P02 P03 P04 P05 P06

Climate (c)

Annual Rainfall S1 (100) S1 (100) S1 (100) S1 (100) S1 (100) S1 (100)


Topography (t)

Slope S1 (100) S1 (100) S1 (100) S1 (100) S1 (100) S1 (100)

Wetness (w)





Soil Fertility (f)

O M S1 (100) S1 (100) S1 (100) S1 (100) S1 (100) S1 (100)

CEC S2 (85) S1 (95) S3 (60) S3 (40) S2 (85) S3 (60)



Potential S1 (76) S1 (90) S2 (72) S3 (43) S3 (43) S2 (72)



Table 15: Suitability Class Scores of the Study Area for Yam

P01 P02 P03 P04 P05 P06

Climate (c)

Annual rainfall S1 (95) S1 (95) S1 (95) S1 (95) S1 (95) S1 (95)


Topography (t)

Slope S1 (100) S1 (100) S1 (100) S1 (95) S1 (100) S1 (100)

Wetness (w)





Soil Fertility (f)

Total. N S2 (85) S2 (85) S2 (85) S2 (85) S2 (85) S2 (85)

Avail. P S3 (60) S3 (60) S3 (60) S3 (60) S3 (60) S3 (60)

Exch. K S3 (60) S3 (60) S3 (60) S3 (60) S3 (60) S3 (60)

pH S2 (85) S2 (85) S2 (85) S2 (85) S2 (85) S2 (85)

CEC S2 (85) S2 (85) S2 (85) S2 (85) S2 (85) S2 (85)



Potential S1 (90) S3 (45) S1 (75) S3 (44) S1(90) S1 (90)



The aggregate suitability scores of land units represented by P01, P02, P03, P04, P05 and P06 for

the individual crop production are as follow:

Cassava

Pedons P01, P02, P03, P04, P05 and P06 have aggregate suitability score values of S1(90),

S3(45), S1(75), S3(44), S1(90) and S1(90) potentially; and S2(57), S3(45), S2(53), S3(44),

S2(57) and S2(57) currently, respectively. Thus,

• Potentially: P01, P03, P05 and P06 are highly suitable; while P02 and P04 are marginally

suitable, respectively.

• Actual (currently): P01, P03, P05 and P06 are moderately suitable; while P02 and P04 are

marginally suitable, respectively.

Maize

The actual suitability scores of pedons P01, P02, P03, P04, P05 and P06 are S2(57), S3(44),

S3(49), S2(53), S2(54) and S2(57), while the potential scores are S1(90), S3(44), S2(69), S1(75),

S1(76) and S1(90), respectively; with the following indications:

• Potentially: P01, P04, P05 and P06 are highly suitable; while P02 is marginally suitable

and P03 is moderately suitable.

• Currently: P01, P04, P05 and P06 are moderately suitable; while P02 and P03 are


Oil palm

The aggregate scores S1(76), S1(90), S2(51), S3(29), S2(51) and S2(51) are respective actual

suitability scores for pedons P01, P02, P03, P04, P05 and P06; whereas S1(76), S1(90), S2(72),

S3(43), S3(43) and S2(72) are their potential aggregate suitability scores, respectively. This

implies that:

• Potentially: P01 and P02 are highly suitable; P03 and P06 are moderately suitable; while

P04 and P05 are marginally suitable, respectively.

• Currently: P01 and P02 are highly suitable; P03, P05 and P06 are moderately suitable;

while P04 is marginally suitable, respectively.

Yam

Pedons P01, P02, P03, P04, P05 and P06 have aggregate suitability score values of S1(90),

S3(45), S1(75), S3(44), S1(90) and S1(90) potentially; and S2(57), S3(45), S2(53), S3(44),

S2(57) and S2(57) currently, respectively. Hence,

• Potentially: P01, P03, P05 and P06 are highly suitable; while P02 and P04 are marginally

suitable, respectively.

• Actual (currently): P01, P03, P05 and P06 are moderately suitable; while P02 and P04 are


The parametric and non-parametric suitability classification of the soil units indicating limitation

characteristics for cassava, maize, oil palm and yam production is shown in Table 16.

Table 16: Aggregate Suitability Scores and Suitability Classification of the Pedons Indicating Limitation Characteristics

P01 P02 P03 P04 P05 P06

Parametric Non-P*

Parametric Non-P* Parametric Non-P

* Parametric Non-P

* Parametric Non-P

* Parametric Non-P

*

CASSAVA

Actual S2 (57) S2f S3 (45) S2wf S2 (53) S2f S3 (44) S2sf S2 (57) S2f S2 (57) S2f

Potential S1 (90) S1 S3 (45) S2w S1 (75) S1 S3 (44) S2s S1 (90) S1 S1 (90) S1

MAIZE

Actual S2 (57) S2f S3 (44) S2wf S3 (49) S2f S2 (53) S2f S2 (54) S2f S2 (57) S2f

Potential S1 (90) S1 S3 (44) S2w S2 (69) S1 S1 (75) S1 S1 (76) S1 S1 (90) S1

OIL PALM

Actual S1 (76) S1 S1 (90) S1 S2 (51) S2f S3 (29) S2sf S2 (51) S2f S2 (51) S2f

Potential S1 (76) S1 S1 (90) S1 S2 (72) S1 S3 (43) S2s S2 (72) S1 S2 (72) S1

YAM

Actual S2 (57) S2f S3 (45) S2wf S2 (53) S2f S3 (44) S2sf S2 (57) S2f S2 (57) S2f

Potential S1 (90) S1 S3 (45) S2w S1 (75) S1 S3 (44) S2s S1 (90) S1 S1 (90) S1

*: Non-P=Non-parametric; f=fertility limitation; w=wetness limitation; s=soil physical characteristic limitation

Major Limitations to Land Suitability

Cassava

Soil units identified by profiles P01, P03, P05 and P06 are moderately suitable (S2f) for cassava

cultivation, while P02 and P04 are marginally suitable (S2wf and S2sf, respectively). The major

limitations are soil depth for P04 and drainage for P02. Other limiting factors are soil fertility,

measured by CEC (4.40 - 12.80 cmol kg-1

), base saturation (<50 %), exchangeable K (0.03 - 0.61

cmol kg-1

), available P (2.8 - 43.84 mg kg-1

) and total N (0.42 - 0.196 %) contents.

The data have shown that in Anuka, two of the five land qualities- topography (slope) and

climate (annual rainfall and annual maximum temperature) are optimum for cassava production.

Also, soil texture and depth as aspects of soil physical characteristics are optimum for cassava

production in all soil units except pedon P04 which is slightly and moderately limited by soil

texture (sandy clay loam/sandy loam instead of loam, sandy clay or clay loam) and depth (0 - 62

cm), respectively. The most serious limiting characteristic to cassava production in Anuka is

fertility. The exchangeable K values of the soils are mostly less than 2.0 cmol kg-1

recommendation, as well as the generally low available P content (<15 mg kg-1

) of the respective

pedons.

Maize

The land units represented by P01, P04, P05 and P06 are moderately suitable (S2f) for maize

production, whereas P02 and P03 are marginally suitable (S2wf and S2f, respectively). The

limitations found are generally soil fertility (f) for all the pedons and wetness (w) specifically for

P02. The pH, CEC and base saturation are slight limitation to maize production for the soil units.

Pedon P02 showed moderate limitation by drainage and available P, and slightly by pH, CEC

and base saturation. For other soil units represented by profiles P01, P03, P04, P05 and P06,

available P is of moderate limitation for their suitability for maize production.

Yam

Wetness is a severe limitation to yam production in soil unit represented by P02, and soil depth

as aspects of soil physical characteristics is a limitation in P04 (Table 6). Soil fertility is another

land quality that severely limits yam production in Anuka soils. Exchangeable K severely limits

its production. CEC and base saturation are of slight limitation to yam production.

Oil Palm

The limiting characteristic of Anuka soils for oil palm production is mainly CEC as an aspect of

soil fertility. Soil depth under soil physical characteristics is optimum for oil palm in all soil units

except the unit represented by P04 (Table 6) with moderate soil depth limitation. Climate and

topography are optimum for oil palm production.

The suitability sub-classes showed that soil fertility was generally low in the study site; while

wetness further limits the suitability of P02 for cassava, yam and maize production; and soil

depth as an aspect of soil physical characteristics limits P04 for yam, cassava and oil palm

production.

Chapter Five

DISCUSSION

Soil Properties

The brighter colours of the soils of land units represented by profiles P01, P03, P04, P05 and P06

are typical of well-drained soils through which water easily passes and in which oxygen is

generally plentiful; while the gray colour of pedon P02 shows prolonged anaerobic condition and

iron oxide influence; indicating that this poorly-drained upslope remains wet throughout the

growing season.

The textural classes of the studied soils indicate remains of weatherable materials (sand, silt or

clay) from the parent materials. Although total sand content did not follow a particular pattern in

all the soils, it decreased with soil depth for pedons P04, P05 and P06. Silt fraction was less in

the subsoils than in the topsoils, while clay content increased with depth. The major factor

affecting particle size distributions in soils of eastern Nigeria is parent material (Akamigbo and

Asadu, 1983).

Sand was the dominant fraction, probably because the soils were derived from sedimentary

rocks. The relative high sand content in the area is the reflection of the effect of a sandy parent

material. The parent materials of the soils of eastern Nigeria have been noted to influence the

texture of the soils derived from them (Akamigbo and Asadu, 1983). The lower silt content in the

soils may also be attributed to the effect of parent materials on the soils, as it has been reported

(Akamigbo, 1984) that silt content is low in most soils of southeastern Nigeria. This is consistent

with Akamigbo and Asadu (1983), that low content of silt-size particles in soils is attributable to

the characteristics of the parent material of the soils.

The relative higher clay content in the subsurface layer than in the surface may have resulted

from the process of eluviation and illuviation (translocation of clay) from the upper horizon to

the B horizon, which resulted in the formation of textural B horizons in the soils. The low clay

content of the upper layer may further indicate the degree of leaching the soil has undergone.

This is evident of Ultisols, formed by the process of clay mineral weathering, translocation of

clays to accumulate in an argillic or kandic horizon and leaching of base-forming cations from

the profile (Brady and Weil, 1999). Idoga and Azagaku (2005) noted that increase in clay with

depth may be the result of eluviation – illuviation processes as well as contributions of the

underlying geology through weathering. According to Malgwi et al. (2000), lower clay content

of the surface horizons could also be due to sorting of soil materials by biological and /or

agricultural activities, clay migration or surface erosion by runoff or combination of these.

The soils of the studied site are generally acidic. The acid nature of the soils may be due to high-

intensity rainfall in the area, which leaches basic cations down the profile. Enwezor et al. (1981)

stated that leaching of Ca and Mg is largely responsible for acidity development in soils. Also, it

may be due to Al saturation of the exchange complex. Acidity (low pH) of the soils may also be

due to the effect of cultivation, erosion and leaching of nutrients or a combination of these.

Nevertheless, the exchangeable acidity values were low as their values were within the range of

0.4 to 5.6 cmol kg-1

. Such range of values may not hinder crop production (Ukpong, 1995).

The organic matter contents are medium (>2.0 %) for epipedons based on organic matter rating

of the Southeastern Nigerian soils by Enwezor et al. (1990). This is evidence of organic material

incorporation into the soils. In all soil units, the values of organic matter content decreased with

soil depth below the critical level. The low values of organic matter would encourage a rapid

leaching of cations into the subsoils from the surface. Thus, the soils are low in ECEC (<12.04

cmol kg-1

) and low in available P and total N. According to Chikezie et al. (2009), the

environment of eastern Nigeria is characterized by high temperature and relative humidity

conditions that favour rapid decomposition and mineralization of organic matter. Therefore,

organic matter content has to be substantially increased through effective crop residue

management.

The phosphorus content of the representative pedons is generally low based on the rating for

Nigerian soils (<15 mg kg-1

) (Enwezor et al., 1990; Adepetu, 2000), except for some epipedons

of medium ratings, 43.84 mg kg-1

and 31.71 mg kg-1

. Generally, the low phosphorus content may

be due to high soil acidity (Uzoho et al., 2004). The P content could be attributed to strongly to

moderate acidic soils (pH < 6.0) which are not conducive for the release of P. It has been

reported that in acid soils, P is fixed by acidic Fe, Al and Mn (Enwenzor et al., 1989). The low

content of total N in the soils could be attributed to inadequate organic matter of these soils. The

levels of nitrogen and phosphorus in the soils may also be due to intensive cropping practices

without measures to build up soil nutrient reserves. Considering the critical value for

phosphorus, the soils under the various land use types may require phosphate fertilizer

application for a sustainable crop yield.

The low CEC may be related to low organic matter content. Lal and Kang (1982) had observed

that the higher the organic matter content of the soil, the higher the CEC. Lombin et al., (1991)

also reported that organic matter content was a major contributor to the CEC of the soil. The low

CEC content of the soil could likely be attributed to high rate of weathering. The values of the

silt/clay ratio of the soils were above 0.25, an indication that the soils are not old soils derived

from old parent materials and are of intense degree of weathering; as old soils usually have

silt/clay ratio less than 0.15, with low degree of weathering. Brady and Weil (1999) pointed out

that the cation exchange capacity (CEC) of most soils increases with pH; thus at very low pH

values, the CEC is also generally low. Exchangeable bases are generally low. There is low

exchangeable Ca (<3.2 cmol kg-1

), low to medium exchangeable Mg (0.2 - 3.2 cmol kg-1

), and

very low exchangeable Na (<0.70 cmol kg-1

) (Landon, 1984). The area also suffers nutrient

deficiency of exchangeable K, which is less than 2.0 cmol kg-1

recommended for soils of

southeastern Nigeria (FPDD, 1989).

With the levels of exchangeable bases, the soils lack adsorptive capacity for nutrients. The low

effective CEC of these soils indicates their low capacity to retain nutrient elements, and low CEC

renders soils unsuitable for intensive agriculture (Kparmwang et al.; 2004). The overall results

especially the acidic nature of the soils and the deficiency of exchangeable bases indicate that the

soils are generally not fertile (base saturation <50 %) (Landon, 1984).

The average abundance of the extractable micronutrients in the soils is in the order: Cu < Mn <

Zn < Fe < B < Mo. The soils have high content of Cu, regarding 0.1 mg kg-1

as its critical level

as proposed by Lindsay and Norvell (1978). The Cu content is anticipated to be higher in the

subsurface soils than has been observed in the surface soils. Chude et al.(1993) observed that Cu

content increase with depth, which also coincided with increase in clay content in the profiles.

The soils are above sufficient values in extractable Fe, Mn and Zn, considering 2.5 mg kg-1

critical value for Fe (Cox and Kamprath, 1972); 1.0 mg kg-1

critical limit for Mn and 0.80 mg kg-

1 marginal limit (Lindsay and Norvell, 1978) for Zn. Takar (1982) reported that there is no

particular relationship of Zn with soil depth. This seems to suggest that the soils are adequately

endowed with micronutrients. Low pH has been reported to cause micronutrient toxicity in soils

(Enwensor et al., 1989). Reports of Deb and Sakal (2002) and Brady and Weil (2002) showed

that the availability of most of the micronutrients in soil depends on soil pH and organic carbon

(OC) contents. Lombin (1983) also reported that the OC and clay fractions of the soil are the

mainstay of extractable micronutrients in the soil. These suggest that the soil pH level should be

maintained at such a range that will not permit excessive levels of these micronutrients in the

soils.

In addition, according to Amhakhian and Osemwota (2012), both pH level and exchangeable K

content are negatively and significantly correlated with B. This indicates that with the low pH

and deficiency of exchangeable K in the soils, B is likely to exceed desirable limit for crop

production at Anuka. It was also reported that exchangeable Na negatively and significantly

correlated with Mo content (Amhakhian and Osemwota, 2012). There is therefore, no doubt that

with the very low exchangeable Na content in the soils of Anuka, extractable Mo takes an

inverse direction; and efforts to improve the soil pH level, as well as exchangeable bases will

ameliorate soil micronutrients for crop production at Anuka.

Soil Suitability

The sampling units are not having the proper crops, as none of the units showed high suitability

for its current utilization type. P01 is moderately suitable for its current utilization (cassava

production). It is also moderately suitable for maize and yam production, but highly suitable for

oil palm cultivation.

P02 and P03 are both only marginally suitable for their current utilization (maize production).

Although P02 is highly suitable for oil palm cultivation, it is marginally suitable for cassava and

yam production. However, P03 is moderately suitable for other utilization types in existence

within the study site.

The current land utilization of P04 is yam production, for which it is only marginally suitable. It

also showed marginal suitability for oil palm and cassava production, but moderate suitability for

maize production. P05 and P06 are not highly suitable for their current land utilization (oil palm

cultivation). They both showed moderate suitability for all the utilization types within the study

area.

Suitability Limitations for Crops

Cassava

The suitability map for cassava production is shown in figure 4. The results of the study show

that in spite of the optimum or near optimal climatic and topographic qualities, in the forms of

annual rainfall, maximum temperature and slope, there is no highly suitable (S1) mapping unit

for cassava production in the study site. The studied soils are moderately (S2) to marginally (S3)

suitable for cassava production. The most severe limitation to cassava production discovered in

the study is soil fertility: moderate limitations by available P and exchangeable K, and slight

limitation by total N, CEC and base saturation, arising from the acidic nature of the soils.

However, if land use types P01, P03, P05 and P06 are improved, taking into consideration those

properties that are easily altered (exchangeable K, total N and available P), they will be highly

suitable for cassava production.

Fig. 4: Suitability Map for Cassava Production

Road

River

Maize

Land qualities: climate (c.), topography (t), wetness (w) and soil physical characteristics (s) are

optimum or near optimum for maize production in Anuka, except land use type P02, which

shows moderate limitation to soil drainage. Organic matter is also optimum, meeting the

requirement of 2-1.2% (0-15cm soil depth) organic matter for highly suitable soils for maize

production. However, available P (<6 mgkg-1

) rated the soils marginally suited for maize

cultivation.

In order to raise the productivity of the land to optimum for maize production, management

techniques should enhance the nutrient supply of the soils: application of organic

fertilizer/materials would enhance land productivity, and appropriate drainage facilities should

be put in place to take care of the excessive moisture for land use type P02. Besides, provision of

irrigation facilities would make dry season farming possible. This will further ensure optimum

land productivity as a result of high insolation and relatively dry environment, thereby avoiding

yield reduction arising from incidence of pests and diseases (Udoh and Ogunkunle, 2012).

The suitability map for maize production at Anuka is represented in figure 5.

Fig. 5: Suitability Map for Maize Production

Oil Palm

Two land use types (P01 and P02) indicated high suitability for oil palm production (Figure 6);

other land use types are moderately suitable, while P04 is marginally suitable. The major

restrictions of land use type P04 for oil palm production are soil depth as an aspect of soil

physical characteristics and soil fertility measured by CEC. The land use type is moderately deep

(62cm) and stony, and the range of CEC value was 4.4-6.0 cmolkg-1

, rating the soil marginally

suitable for oil palm production.

The results of the study did not show improved suitability of the land use types to be optimum

(highly suitable) for oil palm production. This could be attributed to the required soil fertility

characteristics for oil palm: organic matter, CEC and base saturation. According to Udoh and

Ogunkunle (2012), these chemical properties are not easily altered for potential suitability of

soils/land units.

Fig. 6: Suitability Map for Oil Palm Production

Yam

With respect to figure 7, there is no highly suitable land unit for yam production in the studied

soils, though climate and topography are optimum or near optimum. Land use types P01, P03,

P05 and P06 are moderately suitable for yam production, limited mostly by potassium and

nitrogen. On the other hand, land use types P02 and P04 are marginally suitable for yam

cultivation due to wetness (soil drainage) and soil depth, respectively.

The total nitrogen content of the soils is near critical level of 0.15% total N required for

sustainable yam production, and exchangeable K values (0.03-0.61 cmolkg-1

) fall below 2.0

cmolkg-1

exchangeable K. However, there is a high suitability potential for land use types P01,

P03, P05 and P06 for yam production, if their major limitations (low K and N contents) are

improved. Thus, the fertilizer requirement for yam cultivation in moderately suitable land use

types of Anuka soils should be based on N, P and K.

Fig. 7: Suitability Map for Yam Production

Chapter Six

CONCLUSION AND RECOMMENDATIONS

The dominant textural class of the soils is sandy clay loam; a reflection of the parent materials.

The soils are moderately to strongly acidic, available phosphorus low while organic matter is

medium for epipedons. There is low exchangeable Ca, low to medium exchangeable Mg, very

low exchangeable Na and deficient exchangeable K. Total nitrogen content is moderately low to

very low.

The soils are Typic Dystrustults and Aquic Argiustults. They were not highly suitable for their

respective current utilization types. Fertility was a major limitation to the soils’ suitability for

arable crop production in the study site. Wetness further limits the suitability of P02 for cassava,

yam and maize production; and soil depth as an aspect of soil physical characteristics limits P04

for yam, cassava and oil palm production.

Climate is not a constraint to the production of arable crops in Anuka and environ. The

topography of Anuka farmland is suitable for these crops. Soil depths of >75cm, >100cm and

>125cm are considered adequate for good crop of maize/yam, cassava and oil palm, respectively.

All pedons except P02 have good to moderate drainage, while P02 has poor drainage.

The following sustainable soil management techniques are recommended for the studied soils of

Anuka:

1. Use of organic residue/material: Total N, available P, exchangeable bases and base

saturation are in significant amount in soils that receive organic manure; which poultry

manure is a common source.

2. Mineral fertilizer: Due to the side effects of this technique such as acidification, nutrient

imbalance and trace element deficiencies, mineral fertilizer use should be based on soil

test results. Hence, there is the need for balanced fertilizer use.

The land use recommendations for agricultural crops of Anuka are thus:

� Pedon P01 can support the growing of oil palm, cassava, maize and yam. It has nutrient

limitation though, which can be overcome through organic manuring and the use of

balanced fertilizer.

� Pedon P02, which has nutrient and wetness limitation can only support oil palm

production. Enhanced drainage, as well as organic manuring and use of balanced

fertilizer are recommended for its utilization.

� Although pedon P03 has only nutrient limitation, it cannot support maize production. Its

recommended management includes organic manuring and the use of balanced fertilizer.

� Pedon P04, which has fertility and soil depth limitations, can support maize cultivation.

Organic manuring and soil structural management with organic materials are the

recommended improvements for its use.

� Pedons P05 and P06 can support the production of cassava, maize, yam and oil palm.

Their capacities to produce crops are hindered by fertility. This constraint can be

improved like in pedon P01.

The overall land use recommendation for agricultural crops of Anuka soils is summarized in

table 17, thus:

Table 17: Land Use Recommendation for Agricultural Crops of Anuka

Pedon Limiting Factor Crop

Recommendation

Input Recommendatio

P01 Nutrient Oil palm

Cassava

Maize

Yam

Organic manuring and use balanced

fertilizer

P02 Nutrient

Wetness

Oil palm

Organic manuring, use balanced

fertilizer and drainage

P03 Nutrient Cassava

Oil palm

Yam


fertilizer

P04 Nutrient

Soil depth

Maize

Organic manuring and soil structural

management with organic materials.

P05 Nutrient Cassava

Maize

Oil palm

Yam


fertilizer.

P06 Nutrient

Cassava

Maize

Oil palm

Yam


fertilizer.

References

Adeboye, M. K. A. (1994). The physico-chemical properties and evaluation of Kaduna

Polytechnic Farm soils for arable cropping. Spectrum, 1: 36-42.

Adepetu, J. A. (2000). Interpretation of soil test data. In: Simple Soil, Water and Plant Testing

Technologies for Soil Resource Management. IITA Ibadan/FAO Rome, pp. 89-97.

Aderonke, D. O. and Gbadegesin, G. A. (2013). Spatial variability in soil properties of a

continuously cultivated land. African Journal of Agricultural Research, 8(5): 475-483.

Aggarwal, S. G. and Patel, K. S. (1998). Specific method for spectrophotometric determination

of Molybdenum in soil. Microchimica Acta, Springer-Verlag, 129(3&4): 265-269.

Aguilar, J. and Ortiz, R. (1992). Metodología de capacidad de uso agrícola de los suelos. III

Congreso Nacional de la Ciencia del Suelo. Pamplona, Spain, pp. 281-286.

Ajiboye, G. A. and Ogunwale, J. A. (2010). Characteristics and classification of soils developed

over Talc at Ejiba, Kogi State, Nigeria. Nigerian J. of Soil Sci., 20(1): 1-14.

Akamigbo, F. O. R. (1984). The accuracy of field textures in humid tropical environment. Soil

Survey and Land Evaluation, 493: 63-70.

Akamigbo, F. O. R. and C. L. A. Asadu. (1983). The influence of parent materials on the soils of

southeastern Nigeria. East Africa Agricultural and Forestry Journal, 48: 81–91.

Akamigbo, F. O. R. and Igwe, C. A. (1990). Physical and chemical characteristics of four gullied

soils locations in Anambra State, Nigeria. Nigerian Agric. J., 25: 29-48.

Amhakhian, S. O. and Osemwota, I. O. (2012). Physical and chemical properties of soils in Kogi

State, Guinea savanna zone of Nigeria. Nig. J. Soil Sci., 22(1): 44-52

Ande, O. T (2011). Soil Suitability Evaluation and Management for Cassava Production in the

Derived Savanna Area of Southwestern Nigeria. International Journal of Soil Science, 6,

pp. 142-149.

Ande, O. T., Adediran, J. A., Ayoola, O. T. and Akinlosotu, T. A. (2008). Effects of land quality,

management and cropping systems on cassava production in southern western Nigeria.

African Journal of Biotechnology, 7(14): 2368-2374.

AOAC (1990). Official Methods of Analysis. 15th

Edition. Association of Official Analytical

Chemists. Washington, D. C., USA.

Asadu, C. L. A. (2002). Fluctuations in the characteristics of an important short tropical season

‘august break’ in eastern Nigeria. Discovery and Innovation, Kenya, 14(1&2): 92-101.

Asadu, C. L. A. (1990). Comparative characterization of two-foot slope soils in Nsukka area of

eastern Nigeria. Soil Science, 150: 527-533.

Asadu, C. L. A., Obasi, S. C. and Dixon, A. G. O.(2010) Variations in Soil Physical Properties in

a Cleared Forestland Continuously Cultivated for Seven Years in Eastern Nsukka,

Nigeria. Communications in Soil Science and Plant Analysis, 41(2): 123-132

Azis, A. Sunarminto, B. H and Renanti, M. D. (2006). Evaluasi kesesuaian lahan untuk budidaya

tanaman pangan menggunakan jaringan syaraf tiruan. Berkala MIPA, Indonesian, 16(1):

1-6.

Brady, N. C. and Weil, R. R. (2002). The Nature and Properties of Soils. 13th

edition. Pearson

Education. India.

Brady, N.C. and Weil, R. R. (1999). The Nature and Properties of Soils (12ed.). New Jersey:

Prentice-Hall, Inc.

Bremner, J. M. and Mulvaney, C. S. (1982). Total nitrogen. P.895-926. In: Page et al (eds).

Methods of soil analysis. Part 2. 2nd ed. Agron. Monog. 9. ASA and SSSA, Madison.

Chikezie, I. A., Eswaran, H., Asawalam, D. O. and Ano, A. O. (2009). Characterization of Two

Benchmark Soils of Contrasting Parent Materials in Abia State, Southeastern Nigeria.

Global Journal Of Pure And Applied Sciences, 16(1): 23-29.

Chude, V. O.; Amapu, I. Y.; Ako, P. A. E. and Pam, S. G. (1993). Micronutrient research in

Nigeria. A review. Samaru, 10: 17-30.

Chukwu, G. O., Ezenwa, M. I. S., Osunde A. O. and Asiedu R. (2007). Spatial distribution of N,

P and K in major yam soils of southeastern Nigeria. African Journal of Biotechnology,

6(24): 2803-2806.

Cox, F. R. and Kamprath, E. J. (1972). Micronutrient Soil Test. In: Micronutrients in

Agriculture. Soil Science Society of America, Madison, Wisconsin, USA, pp. 289-313.

Deb, D. L. and Sakal, R. (2002). Micronutrients. In: Indian Society of Soil Science. Indian

Research Institute, New Delhi, pp. 391-403.

Dent, D. and Young, A. (1981). Soil Survey and Land Evaluation. George Allen and Unwin Ltd.,

London, UK.

Enwenzor, W. O., Ohiri, A. C., Opuwaribo, E. E. and Udo, E. J. (1990). A review of fertilizer

use on crops in Southeastern zone of Nigeria. In: Literature Review of Soil Fertility

Investigations in Nigeria, FMANR, Lagos, Nigeria, 2: 49-100.

Enwenzor, W. O., Udo, E. J. and Sobulo, R. A. (1981). Fertility status and the productivity of the

acid sands. In: Acid sand of South Eastern Nigeria, Soil Science Society of Nigeria.

Enwenzor, W. O.; Udo, E. J.; Usoroh, N. J.; Ayotade, K. A.; Adepetu, J. A.; Chude, V. O. and

Udegbe, C. I. (1989). Fertilizer use and management practices for crops in Nigeria Series,

2: 63-64.

Esu, I. E. (1999). Fundamentals of Pedology. Stirling-Horden Publishers (Nig.) Ltd., Ibadan, pp.

136.

Esu, I. E. (2004). Soil characterization and mapping for food security and sustainable

environment in Nigeria. Proceedings of the 29th Annual Conference of the Soil Science

Society of Nigeria, University of Agriculture, Abeokuta, Nigeria.

Esu, I. E. and Akpan-Idiok, A. U. (2010). Morphology, physio-chemical properties of alluvial

soils in Adamawa State, Nigeria. Nigerian J. of Soil Sci., 20(1): 15-26.

Ezeaku, P. I. (2011). Methodologies for Agricultural Land Use Planning: Sustainable Soil

Management and Productivity. Great AP Express Publishers Ltd. Nsukka.

FAO (1976). A framework for land evaluation. Soils Bulletin 32. Food and Agriculture

Organization of the United Nations, Rome, Italy.

FAO (2001). Lecture notes on the major soils of the world. In: Driessen, P., Deckers, J. and

Nachtergaele, F. (eds.). World Soil Resources Reports (94), FAO, Rome.

FAO (2006). World reference base for soil resources. A frame work for international

classification, correlation and communication. World Soil Reports (103), FAO, Rome.

FAO (1990). Guidelines for Soil Descriptions, 3rd

Ed., FAO, Rome.

Fischer, G.; Nachtergaele, F.; Prieler, S.; Van Velthuizen, H.T.; Verelst, L. and Wiberg, D.

(2008). Global Agro-ecological Zones Assessment for Agriculture, IIASA, Laxenburg,

Austria and FAO, Rome, Italy.

FPDD (1989). Literature on soil fertility investigation in Nigeria. Federal Ministry of Agriculture

and Natural Resources, Lagos.

Gee, G. W. and Bauder, J. W. (1986). Particle size analysis. P.383-411. In: Klute, A (ed).

Methods of soil analysis. Part 2. 2nd ed. Agron. Monog. 9. ASA and SSSA, Madison.

Hakim, N., Nyakpa, M. Y., Lubis, A. M., Nugroho, S. G., Saul, M. R., Diha, M. A., Go, B. H.

and Bailey, H. (1986). Dasar-Dasar Ilmu Tanah. Universitas Lampung (in Indonesian).

Idoga, S and Azagaku, D.E., (2005). Characterization and classification of soils of Janta Area,

Plateau State of Nigeria. Journal of Soil Science, 15: 16-122.

Jungerius, P. D. (1964). The soil of Eastern Nigeria. Pub. Serv. Geologique du Luxemburg, XIV:

185-198.

Klingebiel, A. A. and Montgomery, P. H. (1961). Land Capability Classification. U. S. Dept.

Agric. Handbook.

Kparmwang, T., Chude, V.O. and Abdullahi, D. (2004). The classification and genesis of

benchmark soils of Bauchi State, Nigeria. Journal of Soil Science,14: 30-39.

Lal, R. and Kang, B. T. (1982). Management of organic matter in soils of the tropics. In: Soil

Management Abstract, 1(2): 152-178.

Landon, J. R. (1984). Booker Tropical Manual. A handbook for soil survey and agricultural land

evaluation in the tropics and subtropics. Booker Agricultural International Ltd, UK.

Lin, H.; Bourma, J.; Wilding, J.; Richardson, L.; Kutilek, M. and Nielson, D. R. (2005).

Advances in hydropedology. Advances in Agronomy, 85: 1-89.

Lindsay, W. L. and Norvell, W. A. (1978). Development of a DTPA soil test for Zn, Fe, Mn and

Cu. Soil Science Society of America, 42: 421-428.

Lombin, G. (1983). Evaluating the micronutrient fertility of Nigeria’s semiarid savanna soils. 2.

Zinc. Soil Sci., 136: 42-47.

Lombin, L., Adepetu, O. J. and Ayotade, K. A. (1991). Complementary use of organic manures

and inorganic fertilizer in arable crop production. Organic Fertilizer in the Nigerian

Agriculture: Present and Future. Proceedings of a National Organic Fertilizer Seminar,

Kaduna, Nigeria.

Malgwi, W. B., Ojanuga, A. G., Chude, V. O., Kparmwang, T. and Raji, B. A. (2000).

Morphological and Physical Properties of some soils of Samaru, Zaria. Nigerian Journal

of Soil Research, 1: 58-64.

McClean, E. O. (1965). Aluminum. In: C. A. Black (ed). Methods of Soil Analysis. Part 2. Amer.

Soc. Agron., Madison Wisc., pp. 978-998.

Nelson, D. W. and Sommer, L. E. (1982). Total carbon, organic carbon and organic matter.

Methods of Soil Analysis. Part 2. Chemical and Microbiological Properties, ASA,

Madison, WI pp.359-580.

Ogunkunle, A. O. (1993). Soil in land suitability evaluation : An example with oil palm in

Nigeria. Soil Use and Management, 9: 35-40.

Ogunkunle, A. O. (2005). Soil Survey and Sustainable Land Management. Proceedings of the

29th

Annual Conference of the Soil Science Society of Nigeria.

Onyekwere, I. N., Chukwu, G. O. and Ano, A. O. (2009). Characteristics and Management of

Soils of Akamkpa Area, Cross River State, Nigeria for increased Cocoyam Yields. Nig.

Agric. J., 40(1): 271-278.

Orajaka, S. O. (1975). Geology. In Nigeria in maps: Eastern States. G. E. K. Ofomata (Ed.)

Ethiope publishing house, Benin city, Nigeria.

Ozcan, H. (2006). GIS based land evaluation of the high land in east Mediterranean region,

Turkey. J. Agric.

Page, A. L.; Miller, R. H. and Keeney, D. R. (1982). Methods of Soil Analysis. Part 2. Chemical

and Microbiological Properties. ASA, Madison.

Ritung, S., Wahyunto, A. F. and Hidayat, H. (2007). Land Suitability Evaluation with a case map

of Aceh Barat District. Indonesian Soil Research Institute and World Agroforestry

Centre, Bogor, Indonesia.

Rossiter, D. G. (1996). A theoretical framework for land evaluation. Geoderma, 72: 165-190.

Senjobi, B. A (2007). Comparative assessment of the effect of land use and land type on soil

degradation and productivity in Ogun State, Nigeria. Published Ph.D. thesis submitted to

the Department of Agronomy, University of Ibadan, Ibadan, pp. 161.

Senjobi, B. A. (2001). Parametric and conventional approaches for soil potential evaluation in

three ecological zones of southern Nigeria. Moor Journal of Agriculture Research, 2(2):

91-102.

Senjobi, B. A. and Ogunkunle, A. O. (2011). Effect of different land use types and their

implications on land degradation and production in Ogun State Nigeria. Journal of Agric.

Biotech and Sustainable Development, 3(1): 7-18.

Soil Survey Staff (1975). Soil Taxonomy. A basic system of soil classification for making and

interpreting soil surveys. 1st edition. USDA Handbook No. 436, US. Govt. Printing

Office, Washington DC, pp. 754.

Soil Survey Staff (1999). Soil Taxonomy. A basic system of soil classification for making and

interpreting soil surveys. 2nd

edition. USDA-NCRS. Agric. Handbook No. 436, US. Govt.

Printing Office, Washington DC, pp. 869.

Soil Survey Staff (2003).keys to soil taxonomy. 9th

Edition. USDA, Natural Resources

Conservation Service, US Department of Agriculture, Washington DC, pp. 306.

Soil Survey Staff (2010). Keys to Soil Taxonomy. United States Department of Agriculture

Natural Resources Conservation Service.

Storie, R. E. (1933). An Index for rating the agricultural values of soils. Calif. Agric. Expt. Sta.

Bull., 566, pp. 48.

Suryana, A., Adimihardja, A., Mulyani, A., Hikmatullah, A. and Siswanto, B. (2005). Prospek

dan Arah Pengembangan Agribisnis: Tinjauan Aspek Kesesuaian Lahan. Badan Litbang

Pertanian, Departemen Pertanian, pp. 32.

Sys et al. (1991). Land evaluation and crop production and calculations. Agric publication, No.

7. General Admin for Development Corporation, Brosels: 247.

Sys, C. (1985). Land evaluation. State University of Ghent, International Training Centre for

post-graduate soil scientists; Algemeen Bestuur van de Ontwikkelingss. Ghent, Belgium.

Takar, P. N. (1982). Micronutrients- forms, content, distribution in profiles, indices of

availability and soil test methods. In: Review of Soil Research in India, pp. 161-184.

Thomas, G. W. (1982). Exchangeable cations. In: Page et al (eds). Methods of soil analysis. Part

2. 2nd ed. Agron. Monog. 9. ASA and SSSA, Madison, WI, pp. 159-165.

Udoh, B. T. ; Henry, H. B. and Akpan, U. S. (2011). Suitability Evaluation of Alluvial Soils for

Rice (Oryza sativa) and Cocoa (Theobroma cacao) Cultivation in an Acid Sands Area of

Southeastern Nigeria. Journal of Innovative Research in Engineering and Science, 2(3).

ISSN : 2141-8225

Udoh, B. T. and Ogunkunle, A. O. (2012). Land Suitability Evaluation for Maize (Zea mays)

Cultivated in a Humid Tropical Area of South Eastern Nigeria. Nig. J. Soil Sci., 22(1): 1-

10.

Udoh, B. T.; Ogunkunle, A. O. and Olaleye, A. O. (2006). Land suitability evaluation for

banana/plantain (Musa spp.) cultivation in Akwa Ibom State of Nigeria. Journal of

Research in Agriculture, 3(3): 1-6.

Ukpong, I. E. (1995). Vegetation and soil acidity of a mangrove swamps in South-Eastern

Nigeria. Soil Use and Management, 11: 141-147.

Uzoho, B. U. and Oti, N. N. (2004). Phosphorus adsorption characteristics of selected

Southeastern Nigeria soils. In: Proceeding of the 29th

Annual conference of the Soil

Science Society of Nigeria, pp. 121-131.

Wahyunto, A., Mulyani, D. and Moersidi, S. (1994). Keadaan Tanah dan Penyebarannya di

Provinsi Maluku. In: H Subardjo, JS Adiningsih, A Mulyani, Irawan, R Syamsulbahri

and SE Aprillani (eds). Prosiding Temu Konsultasi Sumberdaya Lahan untuk

Pengembangan Kawasan Timur Indonesia, Palu 17-20

EZE, NNENNA CHIZOBA REG. NO.: PG/M.Sc/09/50741 ... THESIS.pdfEZE, NNENNA CHIZOBA REG. NO.:...

Documents

Transcript of EZE, NNENNA CHIZOBA REG. NO.: PG/M.Sc/09/50741 ... THESIS.pdfEZE, NNENNA CHIZOBA REG. NO.:...