SOIL HEALTH

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Table of Contents

01. Soil ................................................................................................................................................... 1

1.1. Components of Soil .............................................................................................................. 1

1.2. Soil Profile ................................................................................................................................ 2

1.3. Soil Formation........................................................................................................................ 4

02. Soil Health .................................................................................................................................... 7

03. Factors Controlling Soil Health .......................................................................................... 9

3.1. Soil Type ....................................................................................................................................... 9

3 .2. Organisms and Functions .................................................................................................... 9

3.3. Carbon and Energy ............................................................................................................... 10

3.4. Nutrients ................................................................................................................................... 11

04. Ideal Soil Structure ............................................................................................................... 12

05. Soil Health and Crop Production .................................................................................... 14

06. Reasons for Reduction of Soil Health ........................................................................... 19

6.1. Aggressive Tillage...................................................................................................................... 19

6.2. Annual/Seasonal Fallow .................................................................................................... 20

6.3. Monocropping ......................................................................................................................... 21

6.4. Annual Crops ........................................................................................................................... 21

6.5. Excessive Inorganic Fertilizer Use ................................................................................. 22

6.6. Excessive Crop Residue Removal ................................................................................... 22

6.7. Broad Spectrum fumigant (Pesticides) ....................................................................... 23

6.8. Broad Spectrum Herbicides .............................................................................................. 23

07. Soil Health Management ..................................................................................................... 25

7.1. Conservation Agriculture and Managing Soil Health ............................................ 25

7.2. Practices for Improve Soil Health .................................................................................. 27

7.2.1. No – Till or Conservation Tillage ............................................................................ 27

7.2.1.1. Features of no till or minimum tillage system……………………………29

7.2.2. Mulching and Cover Cropping ................................................................................. 31

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7.2.2.1. Benefits of Mulching/Cover cropping………………………………………..33

7.2.3. Crop Diversification /Crop Rotation ..................................................................... 35

7.2.3.1. Benefits of crop rotations………………………………………………………….36

7.2.4. Use of Organic Fertilizer ............................................................................................. 37

7.2.5 Integrated Pest Management (IPM) ....................................................................... 38

7.2.5.1. The IPM process……………………………………………………………………….38

7.2.5.2. Pest Control Methods……………………………………………………………….39

7.2.5.3. benefits of IPM………………………………………………………………………...40

7.2.6. Integrated Weed Management (IWM) ................................................................. 41

7.2.6.1. Benefits of IWM………………………………………………………..………………42

08. Future Challenges and Opportunities Soil Health Management ...................... 43

09. Bibliography............................................................................................................................. 45

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List of Figures

Figure 1 : Soil Profile ........................................................................................................................... 2

Figure 2: Soil Formation Process ................................................................................................... 4

Figure 3: Functions of Soil: (Source: Brady and Weil, 1996) ............................................ 8

Figure 4:The Importance of Soil Biology for Soil Health .................................................. 10

Figure 5: Ideal Composition of a Soil ......................................................................................... 12

Figure 6: Number of Soil Organism in Health Soil ............................................................... 13

Figure 7: Soil Health Indicators and System .......................................................................... 16

Figure 8: Difference in Water Infiltration in Conventional and No-tillage Practices

.................................................................................................................................................................... 18

Figure 9: How to Reduce Soil Health ......................................................................................... 19

Figure 10: Soil Health Principles ................................................................................................. 25

Figure 11: How to Promote Soil Health ................................................................................... 27

Figure 12: Strip Tilling is One Method to Prevent Loss in Soil Quality due to

Excessive Tilling ................................................................................................................................. 28

Figure 13: Intensive Tillage vs Long Term No-Till.............................................................. 30

Figure 14: Crop Rotation ................................................................................................................ 36

Figure 15: IPM Process .................................................................................................................... 38

Figure 16: Pest Control Methods................................................................................................. 39

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01. Soil

Soils are complex mixtures of minerals, water, air, organic matter, and countless

organisms that are the decaying remains of once-living things. It forms at the

surface of land – it is the “skin of the earth.” Soil is capable of supporting plant life

and is vital to life on earth.

The traditional definition of soil is: dynamic natural body having properties

derived from the combined effects of climate and biotic activities, as modified by

topography, acting on parent materials over time.

1.1. Components of Soil

There are five basic components of soil that, when present in the proper amounts

are the backbone of all terrestrial plant ecosystems.

• Minerals: The larger component of soil is the mineral portion, which

makes up approximately 45% to 49% of the volume.

• Water: is the second basic component of the soil. Water can make up

approximately 2% to 50% of the soil volume. Water is important for

transporting nutrients to growing plants and soil organisms and for

facilitating both biological and chemical decomposition.

• Organic matter: is found in soils at levels of approximately 1% to 5%.

Organic matter is derived from dead plants and animals and such as has a

high capacity to hold on to and/or provide the essential elements and

water for plant growth.

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• Gases: Air can occupy the same spaces as water. It can make up

approximately 2% to 50% of the soil volume

• Micro-organisms: They are found in the soil in very high numbers but

make up much less than 1% of the soil volume. The largest of these

organisms are earthworms and nematodes and smallest are bacteria,

actinomycetes, algae, and fungi.

1.2. Soil Profile

The soil profile is defined as a vertical section of the soil that is exposed by a soil

pit. A soil pit is a hole that is dug from the surface of the soil to the underlying

bedrock. Soil profile has five main horizons (Figure 1).

Figure 1 : Soil Profile

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• Organic Surface Layer (O): - Litter layer of plant residues, the upper part

often relatively un-decomposed, but the lower part may be strongly

humified.

• Surface Soil (A):- Layer of mineral soil with most organic matter

accumulation and soil life. Additionally, due to weathering, oxides (mainly

iron oxides) and clay minerals are formed and accumulated. It has a

pronounced soil structure. But in some soils, clay minerals, iron, aluminum,

organic compounds, and other constituents are soluble and move

downwards. When this eluviation is pronounced, a lighter colored E

subsurface soil horizon is apparent at the base of the A horizon. A horizons

may also be the result of a combination of soil bioturbation and surface

processes that winnow fine particles from biologically mounded topsoil. In

this case, the A horizon is regarded as a "biomantle".

• Sub Soil (B): - This layer has normally less organic matter than the A

horizon, so its colour is mainly derived from iron oxides. Iron oxides and

clay minerals accumulate as a result of weathering. In a soil, where

substances move down from the topsoil, this is the layer, where they

accumulate. The process of accumulation of clay minerals, iron, aluminum

and organic compounds, is referred to as illuviation. The B horizon has

generally a soil structure.

• Substratum (C): - Layer of non-indurated poorly weathered or un-

weathered rocks. This layer may accumulate the more soluble compounds

like CaCO3. Soils formed in situ from non-indurated material exhibit

similarities to this C layer.

• Bedrock (R): - R horizons denote the layer of partially weathered or un-

weathered bedrock at the base of the soil profile. Unlike the above layers, R

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horizons largely comprise continuous masses (as opposed to boulders) of

hard rock that cannot be excavated by hand. Soils formed in situ from

bedrock will exhibit strong similarities to this bedrock layer.

1.3. Soil Formation

Figure 2: Soil Formation Process

Soil

forming

factors

Disintegration

(Physical

breakdown)

Rock and

Minerals

Partially

decompose

d parent

material

Soil

Decomposition

(Chemical

changers)

Soil

forming

processes

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• The process of soil formation is termed ‘pedogenesis’ (Figure 2). Soils

develop from parent material by various weathering processes. Organic

matter accumulation, decomposition, and humification are as critically

important to soil formation as weathering. The zone of humification and

weathering is termed the solum. Soil acidification resulting from soil

respiration supports chemical weathering. Plants contribute to chemical

weathering through root exudates. Soils can be enriched by deposition of

sediments on floodplains and alluvial fans, and by wind-borne deposits.

• Soil mixing (pedoturbation) is often an important factor in soil formation.

Pedoturbation includes churning clays, cryoturbation, and bioturbation.

Types of bioturbation include faunal pedoturbation (animal burrowing),

floral pedoturbation (root growth, tree-uprooting), and fungal

pedoturbation (mycelia growth). Pedoturbation transforms soils through

destratification, mixing, and sorting, as well as creating preferential flow

paths for soil gas and infiltrating water. The zone of active bioturbation is

termed the soil biomantle.

• Soil moisture content and water flow through the soil profile support

leaching of soluble constituents, and eluviation. Eluviation is the

translocation of colloid material, such as organic matter, clay and other

mineral compounds. Transported constituents are deposited due to

differences in soil moisture and soil chemistry, especially soil pH and redox

potential. The interplay of removal and deposition results in contrasting soil

horizons.

• These processes can be very slow, taking many tens of thousands of years.

• Five main interacting factors affecting the formation of soil:

▪ Parent material—minerals forming the basis of soil

▪ Living organisms—influencing soil formation

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▪ Climate—affecting the rate of weathering and organic

decomposition

▪ Topography—grade of slope affecting drainage, erosion and

deposition

▪ Time—influencing soil properties.

• Interactions between these factors produce an infinite variety of soils

across the earth’s surface.

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02. Soil Health

Soil health is defined as the continued capacity of soil to function as a vital living

system, by recognizing that it contains biological elements that are key to

ecosystem function within land-use boundaries. These functions are able to

sustain biological productivity of soil, maintain the quality of surrounding air and

water environments, as well as promoting plant, animal, and human health.

As per Karlen et al (1997), soil health can be described as “the capacity of a specific

kind of soil to function, within natural or managed ecosystem boundaries, to

sustain plant and animal productivity, maintain or enhance water and air

quality, and support human health and habitation”.

Functions of healthy soils (Figure 3):

• Supplies nutrients, water and oxygen for healthy plant growth

• Allows water to infiltrate freely

• Resists erosion

• Stores water

• Readily exchanges gases with the atmosphere

• Retains nutrients

• Acts as an environmental buffer in the landscape

• Resists diseases

• Contains a large and diverse population of soil biota

• Is not acidifying or salinizing

• Has a range of pore spaces to house organisms, nutrients and water

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Figure 3: Functions of Soil: (Source: Brady and Weil, 1996)

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03. Factors Controlling Soil Health

3.1. Soil Type

Particular soil types form in response to the nature of parent material, topography

and environmental factors, such as climate and natural vegetation. Past land

management by humans can alter natural soils considerably, for example by loss

of surface horizons due to erosion, alteration of soil water regime via artificial

drainage, salinization due to poor irrigation practices, loss of natural soil organic

matter caused by arable production or contamination. Thus, land-use and

management are the controlling factors for soil health. A set of fixed characteristics

such as texture, stone content, etc. combine with climate to set an envelope of

possible soil habitat conditions, especially those relating to the soil water regime.

Variable factors such as pH, bulk density and soil organic matter content, which

are influenced by land-use and management, then determine the prevailing

condition of the habitat within the range for a particular soil. These fixed and

variable abiotic factors interact with biotic ones to determine the overall condition

of the soil system and its associated health. Primary biological factors will include

the presence or absence of specific assemblages and types of organisms, the

availability of carbon substrate and nutrients, and the concentrations of toxic

materials.

3 .2. Organisms and Functions

The relationships between community structure and function (Figure 4) are

inevitably complex and a prevalent theme in contemporary soil ecology. They are

underwritten by the three principles of repertoire, interaction and redundancy.

There is some experimental evidence that there may be threshold levels of soil

biodiversity below which functions decline. However, in many instances, this is at

experimentally prescribed unrealistically low levels of diversity that rarely prevail

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in nature. Many studies demonstrate high levels of functional redundancy in soil

communities. It can be argued that high biodiversity within trophic groups is

advantageous since the group is likely to function more efficiently under a variety

of environmental circumstances, due to an inherently wider potential. More

diverse systems may be more resilient to perturbation since if a proportion of

components are removed or compromised in some way, others that prevail will be

able to compensate. However, more diverse systems may be less efficient since a

greater proportion of available energy is used in generating and countering

competitive interactions between components, a situation which may be

exacerbated by the similarity in functional properties and hence potential niche

competition.

Figure 4:The Importance of Soil Biology for Soil Health

3.3. Carbon and Energy

The energy that drives soil systems is derived from reduced carbon that is

ultimately derived from net primary productivity. Carbon is the common currency

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of the soil system, and its transfer with associated energy flows is the main

integrating factor. This suggests that the quantities and quality of different organic

matter pools may be indicative of the state of the soil system, while the flows and

allocations of carbon between assemblages of organisms may provide information

about their relationships to ecosystem functions.

3.4. Nutrients

Nutrients are a controlling input to the soil system and the processes within it.

Their levels and transformations are critical to soil health. After carbon, the cycling

of nitrogen and phosphorus to, from and within the soil system most affects its

dynamics and the delivery of ecosystem services, including agricultural

production. Manipulation of nutrient supplies to increase productive outputs from

the soil system by the addition of fertilizers has been one of the keystones of

agriculture for centuries. Nonetheless, knowledge is limited about the impacts of

nutrient additions on the condition of different assemblages of soil organisms and

thence on their functions.

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04. Ideal Soil Structure

Figure 5: Ideal Composition of a Soil

In general terms, the ideal ratio of solids to water to air in a well-structured soil

profile is approximately 50:23:23, with organic matter (OM) at 4% or greater. It is

shown in figure 5. OM is made up of carbon, nitrogen, phosphorous and potassium,

together with tracer elements. It influences plant growth by affecting soil pH,

assisting structure, easing cultivations, and supplying nutrients.

In addition to these basic factors, many other elements contribute to good soil

structure and health. These include the vast array of micro- and larger organisms

(Figure 6) that co-exist to form the soil ecosystem. Additionally, maintaining the

correct soil mineral balance helps optimize the health and productivity of crops,

plus assists in creating a stable soil structure. Soils with a high Cation Exchange

Capacity (CEC) are capable of providing high levels of nutrients to the crop and the

correct balance of these elements (particularly Ca and Mn) assists soil stability.

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Figure 6: Number of Soil Organism in Health Soil

Adopted from

https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/soils/health/biology/?ci

d=nrcs142p2_053865

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05. Soil Health and Crop Production

Crop production is the preliminary stage of any food chain/ food network. Simply

all the living creatures exists in an eco- system, sustain because of crop production.

As the crop production is much significant; in the other terms the growing medium

of those crops also significant. It means that an important ecosystem service that

the soil provides is to support crop production, upon which humans and many

animals depend for subsistence.

Soils are a crucial ally to food security and nutrition: Food availability relies

on soils: nutritious and good quality food and animal fodder can only be produced

if our soils are healthy living soils. Over the last 50 years, advances in agricultural

technology and increased demand due to a growing population have put our soils

under increasing pressure. In many countries, intensive crop production has

depleted the soil, threatening the soils productive capacity and ability to meet the

needs of future generations.

A healthy soil is a living, dynamic ecosystem, packed with microscopic and larger

organisms that perform many vital functions including converting dead and

decaying matter as well as minerals to plant nutrients (nutrient cycling);

controlling plant disease, insect and weed pests; improving soil structure with

positive effects for soil water and nutrient holding capacity, and ultimately

improving crop production. A healthy soil also contributes to mitigating climate

change by maintaining or increasing its carbon content.

A healthy soil produces healthy crops with minimal amounts of external inputs

and few to no adverse ecological effects (Figure 7). It contains favorable biological,

physical and chemical properties.

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A healthy agricultural soil is one that is capable of supporting the production of

food and fiber to a level, and with a quality, sufficient to meet human requirements,

and to continue to sustain those functions that are essential to maintain the quality

of life for humans and the conservation of biodiversity. Soil health is an integrative

property that reflects the capacity of soil to respond to agricultural intervention

Some important healthy soil functions related to crop production include:

i. Infiltration and storage of water

ii. Retention and cycling of nutrients

iii. Pest and weed suppression

iv. Detoxification of harmful chemicals

v. Sequestering of carbon

vi. Production of food and fiber.

When the soil is not functioning to its full capacity as a result of soil constraints

then sustainable productivity and net farmer profits over the long term are

jeopardized.

5.1. Factors Influencing Soil Health

Soil management practices, cropping systems, and weather conditions influence

soil health. Therefore, a healthy soil that is well managed can increase soil water

infiltration and storage, storage and supply of nutrients to plants, microbial

diversity, and soil carbon storage. Soil organic matter (SOM) is a central soil

property that is heavily affected by management practices, which in turn

influences soil physical, biological, and chemical functions.

The relationships between soil organic matter and management inputs such as

tillage and cropping systems can be documented through the evaluation of soil

health indicators. Those indicators reflect the level of response of the soil system

to different management inputs. Field and laboratory evaluation of these different

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indictors can aid in fine tuning management practices to optimize soil biological,

physical, and chemical functions (Figure 7).

Figure 7: Soil Health Indicators and System

The central soil property that influences soil functions is organic matter. The

organic matter component of the soil system is only a small fraction of the topsoil

horizon (ranging from 1-5% or greater by dry weight depending on the soil type

and other formation factors), but essential for the soil physical, biological, and

chemical functions and general soil ecosystem services. The key services for

production agriculture are: nutrient provision and cycling, pest and pathogen

protection, production of growth factors, water availability, and formation of

stable aggregates to reduce the risk of soil erosion. However, these functions are

sequentially influenced by each other starting with organic matter as the building

block for the well linked functions.

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5.2. Tillage Effect on Soil Health

The increased use of intensive tillage and other management practices in row crop

production systems can increase soil erosion, reduce soil health and water quality,

and the capacity to achieve sustainable agricultural production systems. Soil

erosion is always associated with tillage intensity, especially during the spring

season when soils are most vulnerable to water erosion due to lack of vegetation

or residue cover to protect the soil surface from high rain intensity.

Many factors contribute to this problem, but tillage is the prime contributing

factor. Soils under modern production agriculture have lost significant amount of

their carbon pool because of erosion, decomposition, and leaching. The magnitude

of soil organic carbon (SOC) loss from cultivated soils in the Midwest region of the

United States is estimated to be in the range of 30% to 60% of the amount present

under virgin soil conditions since the conversion from prairie system in late 1800s.

This loss in soil organic matter by cultivation is in part caused by the oxidation of

organic matter and CO2 release in addition to losses through surface runoff and soil

erosion(Figure8).

Soil management and conservation practices that protect soil health are not only

economically and environmentally necessary, but the right approach to sustain

and increase soil resiliency. This can be achieved by adopting conservation plans

that are practical, site specific and an integral component of the overall agriculture

production system to achieve intended objectives.

These conservation plans would include no-tillage and reduced tillage (i.e., strip-

tillage), which leave post-harvest crop residue to cover the soil surface. In addition,

many soil conservation plans include practices such as cover crops, the

construction of grass waterways, terraces, buffer strips, and pasture erosion

control systems with manure application and soil testing.

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Figure 8: Difference in Water Infiltration in Conventional and No-tillage Practices

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06. Reasons for Reduction of Soil Health

Figure 9 shows practices which reduce soil health.

Figure 9: How to Reduce Soil Health

quantities, the effect is on process rates rather than any direct toxic effects.

6.1. Aggressive Tillage

Although in short-term, tillage results a warmer, aerated and competition-free

environment suited to seed germination, aggressive tillage fractures the soil, it

disrupts soil structure, accelerating surface runoff and soil erosion. Tillage also

reduces crop residue, which help cushion the force of pounding raindrops.

Without crop residue, soil particles become more easily dislodged, being moved or

'splashed' away. This process is only the beginning of the problem. Splashed

particles clog soil pores, effectively sealing off the soil's surface, resulting in poor

water infiltration. The amount of soil lost from farmland each year is directly

related to soil structure, levels of crop residue remaining on the soil's surface, and

the intensity of tillage practices. When frequent tillage is sustained over a period

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of years, the impact grows even more severe. A total breakdown of soil structure

and overall soil quality is almost assured. A hardpan can develop, effectively

cutting off root elongation, crop development and yield. Removal of topsoil by

erosion contributes to a loss of inherent soil fertility levels. Approximately half of

plant-available phosphorus is concentrated in topsoil as is nearly all of the plant-

available potassium. Although producers can supply needed crop nutrients to

offset the loss of inherent fertility, the productivity of eroded soils can be restored

by adding inputs only when favorable subsoil material is present. Where

unfavorable subsoils exist (limited rooting depth, coarse sand and gravel, or high

soil densities), there is little or no ability to recover yield losses. The impact on soil

health and productivity is devastating and final.

6.2. Annual/Seasonal Fallow

Leaving soils bare without any active root system can cause significant damage,

not only in terms of potential soil erosion, but also in terms of changes in soil health

and productivity in the following season due to problems such as fallow syndrome.

During the period of leaving soil fallow, several chemical and biological changes

may take place. When soil is left bare without any active root system or under

saturated conditions for an extended period of time, these changes in soil

biological properties can be carried into the next season. Some of these potential

changes are induced by the absence of active root systems in such areas that is

essential in building up the microbial community responsible for nutrient cycling

in the root zone. Because of this, reducing plant residue inputs through the use of

fallow causes a decline in soil OM that starves soil microbes, which in turn limits

the metabolic capacity and biological function of the soil.

Therefore, planting of any annual crop during prevented planting can have

significant value in sustaining such microbial community known as arbuscular

mycorrhizae (AM), which is essential for nutrient cycling such as P.

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6.3. Monocropping

The lack of diversity in a monoculture system eliminates all the functions that

nature provides to plants and the soil. It means that there are no varieties of plant

that naturally provide nutrients to the soil, such as nitrogen-fixing legumes, or

ground cover crops that can be slashed and left to improve the nutrient content of

the topsoil. Hence there are fewer species of microorganism and bacteria on the

soil as there are fewer nutrients available for them to survive on, and it

undermines the integrity of the soil by not having a variety of plants with different

root depths. As the monocropping have eliminated the natural checks and

balances that a diverse ecosystem provides, monoculture production has to find

ways to replicate some of them in order to protect the crop (and the profits from

it). This inevitably means the use of large quantities of synthetic herbicides,

insecticides, bactericides and fertilizers. These chemicals not removes with

harvests and remains in soil and leads to pollute water reserviors. With no ground

cover plants due to monocropping it reduces moisture retention ability of the soil

and increase runoff. Also monocropping eliminates the ground cover crops which

leads to no natural protection for the soil from erosion by wind and rain. No plants

provide leaf litter mulch to replenish the topsoil, which would be eroded anyway.

All of this combines to continually degrade the soil, often meaning that it becomes

useable for agriculture.

6.4. Annual Crops

In contrast, annual-based agricultural systems typically have much greater

nutrient losses – partly due to the removal of agricultural products from the

landscape and frquent disturbances to the soil, but also due to inefficiencies in

internal nutrient cycling and poor synchronization of nutrient availability with

plant demand. Significant degradation of soil chemical and physical properties

occurred in annual crop fields, relative to the unfertilized and annually harvested

perennial lands. Soils under annual crops contained significantly lower amounts

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of SOM, SOC, readily oxidizable carbon (ROC), and total soil N than the perennial.

Hence the moisture retention ability of soil, microbial population in soil, microbial

activities in the soil are declined. Soil exposition is high and due to that the soil

erosion can occur. In long-term, the soil become more infertile and cannot recover.

6.5. Excessive Inorganic Fertilizer Use

Since salt content is one of the most critical characteristics of Inorganic fertilizers;

they are expected to be harmful to agriculture in the long run as salts are harmful

for plants as well as soil. Continuous use of these Inorganic chemical fertilizers

depletes essential soil nutrients and minerals that are naturally found in fertile

soil. When we use inorganic fertilizers excessively; they do not help replenish soil

nutrients and its fertility contrary to the popular belief; but, replenish only

nitrogen, potassium and phosphorous. And we know phosphorous does not

dissolve in water and its overuse may cause hardening of soil. Likewise alkaline

fertilizers like sodium-nitrate develop alkalinity in soil reducing its fertility and

making it barren. So to say; soil fertility and vegetation depend much on the

balanced supply of essential nutrients and minerals. As such, overuse of specific

nutrients may cause imbalance in the supply of soil nutrients further resulting in

soil degradation and the loss of equilibrium of a stable soil. Also can result in

negative effects such as leaching, pollution of water resources, destruction of

micro-organisms and friendly insects, crop susceptibility to disease attack,

acidification or alkalization of the soil or reduction in soil fertility thus causing

irreparable damage to the overall system. They enhance the decomposition of soil

OM which leads to degradation of soil structure.

6.6. Excessive Crop Residue Removal

Crop residue serve as a natural blanket to protect the soil surface. When remove

the crop residue, soil exposition is high and leads insolation, erosive impacts of

raindrops and blowing wind. As the surface sealing is removed, soil hydrological

properties also reduces. Lower the saturated/unsaturated hydraulic conductivity,

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reduce water infiltration/rate, and increasing runoff rate and amount. It leads to

lower the soil mosture content, soil microbial content. Bare soils lose moisture

soon after the protective mulch cover is removed. Also soil compaction increases

and increases the breakdown and dispersion of soil aggregates. Thus it breakes

the aggregate stability of soil. Aggregate stability is one of the soil properties most

sensitive to crop residue removal. It decreases with decrease in surface residue

cover. Surface aggregates in soils without residue mulch are readily dispersed

under the erosive forces of impacting raindrops. Accordingly the soil structure

destroys with the excessive crop removal. Stability of aggregates is positively

correlated with SOM concentration.

6.7. Broad Spectrum fumigant (Pesticides)

Pesticides can move off-site contaminating surface and groundwater and possibly

causing adverse impacts on aquatic ecosystems. They can be moved from soil by

runoff and leaching, thereby constituting a problem for the supply of drinking water

to the population. Also it reduces the soil quality by reducing capacity of the soil to

filter, buffer, degrade, immobilize, and detoxify. Heavy treatment of soil with

pesticides can cause populations of beneficial soil microorganisms to decline. Overuse

of pesticides have effects on the soil organisms that are similar to human overuse of

antibiotics. Indiscriminate use of chemicals might work for a few years, but after

awhile, there aren't enough beneficial soil organisms to hold onto the nutrients. For

example, plants depend on a variety of soil microorganisms to transform atmospheric

nitrogen into nitrates, which plants can use. Common landscape herbicides disrupt

this process: triclopyr inhibits soil bacteria that transform ammonia into nitrite.

6.8. Broad Spectrum Herbicides

The risk of environmental pollution through the leaching of pesticides out of soils

into water bodies is affected by how strongly the compound is sorbed to soil. Some

pesticides like glyphosate have strong sorption characteristics, reducing the risk

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of leaching. Hence the retention of glyphosate in soils and water bodies is high and

it badly affect for some soil organisms. Herbicides can harm non-target organisms,

particularly amphibians, symbiotic mycorrhizal fungi or earthworms. They can

reduce the activitity and reproduction of the earthworm. Thus the service come

from earthworms like shredding plant litter, mineralising it and soil organic

matter in their guts, and producing casts that enhance soil nutrient availability and

promote plant productivity. Their burrowing enhances soil root penetration and

water infiltration. Also Arbuscular mycorrhizal fungi (AMF) improve water access

and soil minerals for plants, improve drought tolerance and help with resistance

against pathogens. Recent research has found that glyphosate (and/or its

metabolite AMPA) reduces the spore viability and root colonisation of AMF, and

could reduce plant diversity.

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07. Soil Health Management

7.1. Conservation Agriculture and Managing Soil Health

Figure 10: Soil Health Principles

Basic Soil health management principles are (Figure 10);

- minimize soil disturbance it means reduce or minimize soil tillage

- maximize soil cover it means improve mulching

- maximize biodiversity

- maximize continuous living roots

Conservation agriculture is an agricultural system which has much concern on the

soil health. ‘Conservation agriculture (CA) is not business as usual, based on

maximizing yields while exploiting the soil and agro-ecosystem resources. Rather,

CA is based on optimizing yields and profits, to achieve a balance of agricultural,

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economic and environmental benefits. It advocates that the combined social and

economic benefits gained from combining production and protecting the

environment, including reduced input and labor costs, are greater than those from

production alone. With CA, farming communities become providers of more

healthy living environments for the wider community through reduced use of

fossil fuels, pesticides, and other pollutants, and through conservation of

environmental integrity and services’ (Dumanski et al., 2006). It has three main

principles. They are;

- minimum soil disturbance

No tillage is defined as a way to farm without disturbing the soil through

tillage. No tillage must leave at least 30% of area covered by plant residues

right after crop establishment, and crops are sown using machinery which is

able to place seeds through plant residues from previous crops. The

agronomic practice that best characterizes conservation agriculture for

annual crops is no tillage/ minimum tillage, which has the highest degree of

soil conservation in annual crops, since the mechanical tillage of the ground

is completely suppressed.

- permanent soil cover (mulching)

Groundcovers is the most widely used conservation agriculture agronomic

practice for perennial crops, whereby the soil surface between rows of trees

remains protected against erosion. With this technique, at least 30% of the

soil not covered by the canopy is protected either by sown cover crops,

spontaneous vegetation or inert covers, such as pruning residues or tree

leaves.

- crop rotation and intercropping

These practices reduce requirements for pesticides and herbicides, control

off-site pollution, and enhance biodiversity.

27

According to principles related to soil health and conservation agriculture,

conservation agriculture helps to maximize soil health.

7.2. Practices for Improve Soil Health

Below practices (Figure 11) tend to promote soil health.

Figure 11: How to Promote Soil Health

7.2.1. No – Till or Conservation Tillage

Conservation tillage is a tillage system that conserves soil, water and energy

resources through the reduction of tillage intensity and retention of crop residue.

It involves the planting, growing and harvesting of crops with limited disturbance

to the soil surface.

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Figure 12: Strip Tilling is One Method to Prevent Loss in Soil Quality due to Excessive Tilling

Source: Idowu and Flynn, 2013

Reduced or minimum tillage practices can lead to an accumulation of soil organic

matter. Soil organic matter is rapidly lost through conventional plow-disk tillage

practices. Conventional tillage, which involves turning over the entire plow depth,

exposes large quantities of soil organic matter to oxidation. With reduced tillage

practices, such as no-till, strip-till (Figure 12) or zone-till, smaller amounts of soil

organic matter are exposed to oxidation, which leads to more organic matter in the

soil profile over a long period of time. Reduced tillage can be challenging to

implement, especially when new tillage tools become necessary, and may require

considerable financial outlay. However, through careful thinking, planning, and

consultation with experts, growers can work out adaptable reduced tillage

practices on their farms, which can ultimately benefit soil health and sustainable

productivity of the soil.

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7.2.1.1. Features of no till or minimum tillage system

1. Soil conservation

- Soil erosion can be reduced through leaving the soil untilled.

- Runoff is reduced by more than half in the no-till soils when

compared with tilled soil.

2. Water conservation

- The improved infiltration is an important characteristic of the no-till

system

- The mulch cover and the higher organic matter content under ‘no-till’

increases the retention of soil moisture and decreases evaporation

losses from the soil

3. Soil fertility

- Soil organic matter contents are usually higher and bulk densities

lower under ‘no-till’ than under conventional tillage system

- Large quantities of nutrients and organic matter are saved from

erosion by the ‘no-till’ methods

Table 1: The Loss of Organic Matter according to Tillage

Types of Tillage Organic Matter Lost in 19

Days, (Kg/ha)

Mould board plough + disc harrow

(2x)

4300

Mould board plough 2230

Disc harrow 1840

Chisel plough 1720

Direct seeding 860

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According to table 1, in direct seeding; it means no till organic matter loss is

lower than others. So that no till or conservation tillage enhance soil

fertility.

4. Soil temperatures

- Soil temperatures and diurnal fluctuations usually observed to be

lower under ‘no-till’.

5. Crop yields

Figure 13: Intensive Tillage vs Long Term No-Till

Adopted from http://www.omafra.gov.on.ca/english/environment/bmp/no-

till.htm)

- Zero tillage’ and ‘minimum tillage’ systems give better crop yields

than the conventional methods of cultivation.

- Figure 13 is showed how to root system penetrate in conventional

and conservation tillage. In conventional tillage, soil is compact

within the time and can’t penetrate roots in deep layer of soil. But in

conservation tillage, can penetrate root in deeper layer of soil and

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well distributed. Reasons for that, soils are not compacted in

conservation tillage. Other thing is soil fertility is higher in

conservation tillage soil than conventional tillage soil. So that crop

yield is increased in conservation tillage soil.

6. Weed control

- Weed control is the most problematic situation in no-till system.

However, a holistic strategy should be used for controlling weeds

under no till system.

- Planting cover crops and increasing planting density are some ways

to do that.

7. Energy, time and economics

- Tillage, both mechanical and manual, is highly energy consuming but

‘No-till’ techniques have shown a remarkable reduction in the energy

required.

- Power requirement involved in farming ‘no-till’ and conservation

tillage is shown dramatic saving in time and energy than

conventional tillage.

When considering above features, no tillage / conservation tillage practice helps

to improve soil health.

7.2.2. Mulching and Cover Cropping

Mulch is a layer of crop residue placed on the soil surface. Mainly mulch can be

divided in to in situ and live mulch. The term in situ mulch refers to the residues

of dead or chemically killed cover crops which are used on the same land on which

they were grown. The live-mulch system is a crop production technique in which

food crops are planted directly in a low-growing cover crop with minimum soil

32

disturbance. Its main advantage is that it smothers weeds, and it can play an

important role in soil conservation and maintenance of soil fertility.

Using cover crops can benefit soil health and crop productivity in the long run.

Cover crops are planted between cash crops to protect the soil from erosion and

improve soil health and fertility.

Examples for live mulch legume species:

Pueraria phaseoloides Centrosema pubescens

Arachis prostrate Macroptilium atropurpureum

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Psophocarpus palustris

7.2.2.1. Benefits of Mulching/ Cover Cropping

1. Control soil erosion

Cover crops can provide protection during the periods when a primary crop

is not present. Plant residues reduce the impact of raindrops that otherwise

would detach soil particles and make them prone to erosion. Surface runoff

is slowed by the cover, allowing improved moisture infiltration. Not only

does the above ground growth provide soil protection, but also the root

system helps stabilize the soil by infiltrating the profile and holding it in

place. Cover crops and their decaying residues reduce pollution by

preventing runoff of nutrients and pesticides into surface water.

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2. Add organic matter to soil

Although increases in soil organic matter occur slowly over time, including

cover crops in the rotation can help maintain or slightly increase soil

organic matter. As organic matter and plant residues degrade, they produce

compounds that cement soil components together into aggregates, resulting

in improved structure and tilth. Aggregates contribute to greater soil

permeability, aeration, water infiltration and holding capacity, cation

exchange capacity, and ease of crop emergence and root growth.

3. Recycling or scavenging unused nutrients

Certain cover crops tend to be very efficient at recycling or scavenging

excess nutrients. When the cover crop dies or is removed as forage, some of

the nitrogen will be released and reused by future crops or utilized as

protein in the feed.

4. Increase diversity of beneficial organism

Increased plant residues and the tillage practices generally associated with

cover crop systems may improve the soil environment for certain beneficial

organisms. Organisms such as earthworms, insects, and microorganisms

can improve soil quality and increase nutrient availability by quickly

decomposing organic matter and plant residues. Earthworms in particular

help improve water infiltration and soil structure. Other insects that are

attracted to the cover crop vegetation may provide benefits by preying on

harmful pests.

5. Partial weed control

Cover crops partially control some weeds by competing with them for light,

moisture, nutrients, and space. Cover crops and their residues can act as

mulches or physical barriers by smothering weeds, suppressing weed seed

germination and growth, and lowering soil temperatures. Allelopathic

35

compounds which are released from living or decaying plant tissue,

chemically interfere with weed growth.

6. Fixation of atmospheric nitrogen

Legumes, in association with certain bacteria, have the ability to acquire and

fix nitrogen from the atmosphere. When high nitrogen legume residues

remain in the field, they break down and release nitrogen and other

nutrients, which can then be used by subsequent crops.

7. Possible feed source

Certain cover crops, especially grass species, also can be used for livestock

feed. These crops can be grazed or mechanically harvested as haylage or

hay. With proper management, grazing will have a similar effect, because

even though the tops are harvested or grazed, root mass and stubble remain

to provide protection from erosion.

7.2.3. Crop Diversification /Crop Rotation

Crop rotation is the practice of growing a series of dissimilar/ different types of

crops in the same area in sequential seasons. Good crop rotation can mitigate soil-

borne diseases and improve soil health Rotation is the sequence of crop cultivation

on the farm. It is usually a better farming practice to alternate crops of different

families from season to season or year to year (Figure 14). For instance, cereals

(small grains) can follow legumes such as alfalfa or beans since legumes can fix

nitrogen, which will benefit the following cereal crop after the legume residue has

been worked into the soil. Planning a rotation is farm-specific and is often based

on many factors, including soil type, equipment, water availability, and markets.

36

Figure 14: Crop Rotation

7.2.3.10. Benefits of crop rotation

1. Many crops may have positive effects on succeeding crops in the rotation,

leading to greater production overall.

2. Rotation are used to reduce pests and diseases in the cropping system and

to control weeds by including smothering crop species (e.g. cowpeas) or

green manure cover crops.

3. Improved soil quality (more or deeper roots; root exudates).

4. Better distribution of nutrients in the soil profile (deep-rooted crops bring

up nutrients from below).

5. Increase biological activity.

6. Through rotations, peak labor times may be reduced and labour better

distributed throughout the year if planting and harvest times are different.

Legume Root

FruitLeaf

Onions, Garlic, Beets, Carrots,Radishes

Tomatoes, Cucumbers,Peppers, Eggplant,Melons

Beans, Peas, Lima beans, Potatoes

Lettuce, Herbs, Spinach

37

7. Crop rotations may decrease the risk created by extreme weather events

such as droughts or floods and their effects, as bad seasons or bad parts of

a season may affect some crops more than others.

8. Crop rotations can balance the production of residues by alternating crops

that produce few and/or short-lived residues with crops that produce a lot

of durable residues.

Crop rotation practice reduces requirements for pesticides and herbicides,

control off-site pollution, and enhance biodiversity. The objective is to

complement natural soil biodiversity and to create a healthy soil

microenvironment that is naturally aerated, better able to receive, hold and

supply plant available water, provides enhanced nutrient cycling, and better

able to decompose and mitigate pollutants. Crop rotations and associations can

be in the form of crop sequences, relay cropping, and mixed crops.

7.2.4. Use of Organic Fertilizer

Organic amendments can help build up the soil organic matter and consequently

improve the overall soil quality. Many materials are available as organic

amendments, including manure, compost, and guano, among others. Organic

amendments vary in how much nutrients they can supply to the crop, and it is

therefore important to know the nutrient composition of the amendment material.

The amount of nutrients that can be made available from an organic amendment

depends on the initial nutrient content in the material, its C: N ratio, its soil

mineralization rate (which in turn is dependent on soil temperature and

moisture), and existing levels of soil nutrient (based on soil test). It is a good

practice to send the organic material to a laboratory for analysis so as to determine

the quantity of amendment to add to the soil for meeting plant nutrient demands

38

that can’t be supplied by the soil itself. Note that adding large quantities of compost

with only modest concentrations of nutrient elements can add significantly to the

soluble salt level in the soil.

7.2.5 Integrated Pest Management (IPM)

IPM is a system that maintains the population of any pest, or pests, at or below the

economic threshold level that causes damage or loss, and which minimizes

adverse impacts on society and environment. Two or more pest control methods

such as biological, cultural, mechanical and chemical are used.

7.2.5.1. The IPM process

IPM process has four steps (Figure 15). In the first step, identify the problem by

observing the plant. Secondly, look at the problem is severe or problem is below

or above economic threshold level. According to condition of problem, appropriate

treatment methods (biological, mechanical, cultural or chemical) are selected in

thirdly. Finally, selected treatment method should apply.

Figure 15: IPM Process

Identify• Observe the plant and find the source of the problem

Assess• How large is the problem

Choose

• Select an appropriate treatment method• Always balance effectiveness with impact

Apply• Impement the treatment method

39

7.2.5.2. Pest Control Methods

Main pest control methods are biological method, mechanical method, cultural

method and chemical method (Figure 15).

I. Biological control method

• Biological organisms are manipulated to control pest.

• In here predators/ parasites are released in to the field.

Figure 16: Pest Control Methods

II. Cultural control method

• Cultural control method is agronomic practices that are designed to

optimize growing conditions for the crop. Anything that increases a crop’s

competitive edge will result in increased tolerance to pests often resulting

in reduced pesticide use.

• Unfavorable conditions are created for the pest.

• Examples for cultural control

- Changes in frequency or timing of irrigation

- Pruning to increase air circulation or prevent contact with soil

- Field sanitation between cropping

Biological Control

Manipulation of biological organism

Cultural Control

Agronomic practices

Mechanical Control

Uses machinery and/or other tools to control pests

Chemical Control

Use of bio-rational or synthetic chemical compounds to kill

pest

IPM

40

III. Mechanical control method

• Machinery and/or other tools such as tillage, physical barriers are used to

control pests.

• Row cultivation is an example of mechanical pest control.

• Row cultivation can be used as a stand-alone pest control practice or in

conjunction with a herbicide program.

• Also, some vegetable growers will use a barrier of black plastic to control

pest.

IV. Chemical control method

• Bio-rational or synthetic chemical compounds are used to kill pest.

• Various types of commercially produced chemical pesticides (liquid

pesticides, solid poisons, fumigants, herbicides, fungicides) are used.

• Bio-rational such as Neem leaves or seeds, hot pepper, tobacco, wood ash,

soap, vegetable oil are also can be used.

• The chemical sex attractant (Pheromones) used by many insect species to

draw mates.

• Repellants is a way to prevent pest insect damage is to repel them with a

substance that can be sprayed on the plants (Garlic barrier, Hot pepper wax,

Neem extracts, Pyrethrins, Rotenones)

7. 2.5.3. Benefits of IPM

• Encourage Biodiversity

In IPM, usually practice eco- friendly methods such as biological, cultural. It

minimizes application of chemical method. Hence, soil macro and

microorganisms are conserved in and give better environment for those

organisms.

41

• Usually less expensive

Traditionally, the use of the pesticides to control the pest invasion would

account to lots of cost. Also, these pesticides need to be imported as well the

application of IPM would lessen the financial burden. Moreover, different

techniques involved in IPM are more sustainable with long lasting benefits.

• Minimizes hazards of pesticides

It is obvious that in an IPM schedule the use of pesticides will be

considerably reduced, hence the pesticide residue hazards will also get

automatically minimized.

In IPM, crop rotation, conservation tillage like cultural practices are

practiced. Planting the same crops year after year can lead to a buildup of

crop pests and reduced soil fertility. Crop rotation breaks the life crop-

specific or over-winter on-site. Rotation can significantly reduce pesticide

use. Due to conservation tillage, soil erosion is reduced. So that, soil and

water conditions are enhanced, and improve soil health, tilth, and increase

crop vigor.

7.2.6. Integrated Weed Management (IWM)

An integrated weed management can be defined as the combination of two or

more weed-control methods at low input levels to reduce weed competition in a

given cropping system below the economical threshold level.

Varieties of technologies are used in a single weed management with the objective

to produce optimum crop yield at a minimum cost taking in to consideration

ecological and socio-economic constraints under a given agro-ecosystem.

42

IWM is a system in which two or more methods are used to control a weed. These

methods may include cultural practices, natural enemies and selective herbicides.

7.2.6.1. Benefits of IWM

• It shifts the crop-weed competition in favour of crop

• Prevents weed shift towards perennial nature

• Prevents resistance in weeds to herbicides

• No danger of herbicide residue in soil or plant

• No environmental pollution

• Gives higher net return

• Suitable for high cropping intensity

43

08. Future Challenges and Opportunities Soil Health Management

Four key areas where future challenges and opportunities exist are identified to

advance the agro ecological management of soil health.

• Opening the black box:

The notion of the soil as a living resource whose health is essential for

agricultural sustainability is emerging as it becomes possible to ‘see’ soil

biota more clearly within what was previously considered a ‘black box’.

Using the growing suite of new technologies to open this black box will

allow us to develop a more generalizable understanding about how to

manage soil biodiversity and function. This is particularly important in the

context of the demands of climate change adaptation.

• Above-ground/below-ground interactions:

Developing a better understanding of the way in which agricultural

management and soil biota interact is a necessary prerequisite to determine

the plant densities, arrangements, species and management systems that

are needed to generate a sufficient quantity and quality of biomass, while

maintaining the essential ecosystem functions provided by soil biota in

agricultural landscapes.

• Mapping soil-based ecosystem services:

Identifying, quantifying and mapping hotspots of ecosystem service

providers will contribute to a predictive knowledge of soil-based ecosystem

services. This includes the temporal and spatial dynamics of ecosystem

service provision resulting from various environmental factors.

44

• Soil health monitoring systems:

Developing local soil health monitoring systems to evaluate ecosystem

service provision performance can help to guide local policy (e.g. as part of

payments for ecosystem services schemes), while complementing national

and international monitoring systems that are aimed at high-level natural

resources management and policy.

45

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