EFFECT OF SALINITY ON PHYSICAL AND CHEMICAL PROPERTIES OF SOILS OF KHULNA REGION
Transcript of EFFECT OF SALINITY ON PHYSICAL AND CHEMICAL PROPERTIES OF SOILS OF KHULNA REGION
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Final Report 1. Title of the research project: EFFECT OF SALINITY ON PHYSICAL AND CHEMICAL PROPERTIES OF SOILS OF KHULNA REGION 2. University where research is being carried out: Soil Science Discipline Khulna University, Khulna-9208 3. (a) Name of the Project Director: Dr. Mizanur Rahman Bhuiyan (b) Address: Soil Science Discipline, Khulna University, Khulna-9208 (c) Academic Qualification of Project Director: M.Sc. (Soil Science), Ph. D. (d) Research Assistant: Ms. Roxana Ahmed, M.Sc. 4. Date of Initiation and duration of the Project: 01 November 2005 & 1(one) Year 5. (a) Total Amount Sanctioned: Taka 80,000/- (b) Amount Received: Taka (c) Amount Spent: Taka 6. Introduction: Salinity is one of the most important problems of coastal belt of Bangladesh. Saline
soils, as they contain high concentration of soluble salts are not very suitable for normal
agricultural practices. The coastal offshore area of Bangladesh includes tidal, estuarine and
meander river floodplains. The tidal floodplain land occurs mainly in the south of the Ganges
river floodplain and also on different parts of Chittagong coastal areas. The Ganges tidal
floodplain constitutes about 49% of the coastal areas (Karim et al., 1982). The total amount
of sediment that Bay of Bengal receives is about 1.7 x 109 ton per year. When the deposited
alluvium comes to the contact of sea water it becomes saline. The degree of salinity varies
mainly with season and intensity of tidal flooding (SRDI, 2003). At present total extent of
salt affected soils in Bangladesh is about 10, 20,750 ha. In Khulna, Bagerhat and Satkhira
district the extent of saline soil is about 4,17,460 ha in 2000 which is about 40% of total
saline soil. The recent survey has indicated that the total saline soil of Bangladesh is
increasing. According to SRDI, 2003 the total extent of saline soil was 8,33,450 ha in 1973
and while in 2000 it becomes 10,20,750 ha. Over the last three decades total salt affected
areas increase by 22.47% which is very much alarming. Recent satellite imagery shows that
the non-saline soils of coastal and other regions are gradually becoming saline. This may be
due to withdrawal of water by India during dry season, introduction of brackish water for
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shrimp cultivation, faulty management of sluice gates, regular saline tidal water flooding in
unpoldered area, capillary upward movement of soluble salts due to presence of high saline
ground water table at shallow depth (SRDI, 2003). The salinity has very significant effect on
physical, chemical and biological characteristics of soil. The hydraulic properties, the
aggregate stability, soil strength and soil aeration are influenced by soil salinity. The changes
in soil physical behavior are controlled by salt characteristics of the saline soil (Kaur, 1994).
Soil salinity also affects nutrient availability and microbial transformations in soil (Swarup,
1994). The existing reports on soil salinity mainly deals with the chemical properties of salt
affected soil and little light has been put forward to evaluate physical properties and to
determine the changes in microbial processes in saline soils. Apart from the evaluating the
physical and chemical properties of saline soil it is also very important to evaluate the effect
of salt water intrusion in non saline soils because the soil salinity has been expanding its
claws over Bangladesh. The intrusion of salt water will change the aggregate stability of soil
by enhancing the rate of slaking. The rate of slaking is controlled by salt characteristics, salt
concentration and exchangeable sodium percentage of soil (Rost and Rowles, 1941). The
rapid slaking can seal the pores and decrease hydraulic conductivity, water retention
characteristics and aeration capacity of soil. It is inevitable to determine the rate of change in
nutrient availability and microbial processes due to the increase in salt concentration. This
information will help to adopt best measures for managing the saline soils.
The aim of this research work is to investigate the effect of saline water application on
physical and chemical properties of soils.
7. Materials and Methods:
7.1. Experimental Design: A laboratory incubation experiment was carried out to assess the effect of salt water
intrusion in non saline soils. Two non saline soils were selected from Ganges Meander
floodplain of Khulna division. A calcareous (C) and a non calcareous (NC) soil of Silt loam
texture were selected. Saline water (13 dSm-1) was collected from the river at Shamnagar,
Satkhira district. The salinity treatments were 0, 6.5 and 13 dSm-1 in both soils. Analyses of
treatment water are presented in Table 1. Each salinity treatment was replicated three times.
The treated soils were then incubated in laboratory condition for 7, 15, 30, 60 and 120 days.
The water content of the incubated samples was maintained at field capacity. The symbols
used in the experiment were presented in Table 2. Soil pH, EC, available N, P, K, S, Ca and
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Mg were determined after each sampling. The changes in micro-aggregation were analyzed
prior and after the completion of incubation.
Table 1. Analyses of treatment water
Salinity
pH P S04
2- K+ Ca2+ Na+ Cl- HCO3-
(dS m-1) (g g-1) (cmol(+)kg-1)
0 7.97 0.03 0.00 0.00 0.00 0.00 0.00
0.00
6.5 8.3 0.03 7.13 0.54 1.25 4.18 50.00
244.00
13 8.44 0.05 18.15 1.38 3.20 10.56 67.50
305.00
Table 2. Symbols used in the experiment
Salinity
(dS m-1)
Soils
Calcareous soil Non calcareous soil
0 C0 NC0
6.5 C6.5 NC6.5
13 C13 NC13
7.2. Methods of Analyses 7.2.1. Particle size analysis: The particle size analysis of the soils was carried out by
combination of sieving and hydrometer method as described by Gee and Bauder (1986).
7.2.2. Microaggregate analysis: Soil structure was evaluated by microaggregate
analysis of the soils following the method Kachinskii (1965) with the exception that
hydrometer was used to determine the particle size distribution instead of pipette method.
The state of aggregation and dispersion factor were calculated by the using the following
equations (Baver and Rhoades, 1932)
State of aggregation = ba Dispersion factor = 100
yx
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Where a = percentage of aggregates larger than a specified size in microaggregate analysis, b
= percentage of particles larger than a specified size in particle size analysis, x = percentage
of clay in microaggregate analysis and y = percentage of clay in particle size analysis.
7.2.3. Soil pH: Soil pH (2:1) was determined electrochemically with the help of glass
electrode pH meter as suggested by Jackson (1973).
7.2.4. EC: The electrical conductivity of the soil was measured at a soil water ratio of
1:1 by EC meter (USDA, 2004).
7.2.5. Available P: After extraction of soil sample with 0.5M NaHCO3 (pH 8.5)
solution (Olsen et al., 1954) the concentration of P was determined by ascorbic acid blue
color method (Murphy and Riley, 1962).
7.2.6. Available S: After extraction of soil with 500 ppm of P from Ca-phosphate
(Fox et al., 1964) the concentration was determined by turbidity method as described by
Hunt, 1980.
7.2.7. Water Soluble and Exchangeable Na+ and K+: Exchangeable Na+ and K+ was
extracted with 1N NH4OAc solution (pH 7.0) as described by piper (1950) and Jackson
(1973) and then analyzed by Flame Photometer. Water soluble sodium and potassium was
determined after extraction with distilled water.
7.2.8. Water Soluble and Exchangeable Ca2+ and Mg2+: Exchangeable Ca2+and
Mg2+ was extracted with 1N NH4OAc solution (pH 7.0) as described by piper (1950) and
Jackson (1973) and then analyzed by atomic adsorption spectrophotometer.
7.2.9. Chloride: Water soluble chloride was determined by titration with silver nitrate
as described by Reitemeier (1943).
7.2.10. Bicarbonate: Bicarbonate was determined by titration with sulfuric acid as
described by Reitemeier (1943).
7.3. Statistical Analysis: The data was analyzed statistically by MINITAB (release 13.20). 8. Results:
8.1. Particle size and Microaggregate analysis: The percentages of sand, silt and clay in calcareous soil were 13.05, 55.0 and 31.95, respectively. The percentages of soil separates slightly varied in non-calcareous soil where
the percentages of sand, silt and clay were 13.05, 52.5 and 34.45, respectively. State of
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aggregation slightly increased due to saline water application whereas dispersion factor
showed slight variation (Fig. 1-2).
8.2. Soil pH: Soil pH was increased during 15 days incubation. After 15days pH of the soil tended to decrease slightly in both soils. The change of soil pH was higher in higher salinity
treatments in both calcareous and non-calcareous soils (Fig. 3). In the calcareous soil the
change of pH was higher than the changes in non-calcareous soil. The effect of saline water
application was significant in calcareous (p
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15 days of incubation in all salinity treatments except 6.5 dS m-1 salinity treatment in non-
calcareous soil. This increment was followed by another sharp decrease after 30 days
incubation with few exceptions. However, after 60 days the S concentration tended to be
leveled off. Initially changes in S concentration due to salinity treatment was higher in non-
calcareous except in 6.5 dS m-1 treatment but in later stage S concentration was higher in
calcareous soil in 13 dS m-1 treatment. The effect of salinity treatment was statistically
significant (p
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The increase in Mg concentration was higher in higher salinity treatment in both calcareous
and non-calcareous soils.
8.9. Available Na: Available Na content was increased in both calcareous and non-calcareous soils with the
salinity treatments (Fig. 10). The increase in Na concentration was lowest in 0 dSm-1 salinity
treatment and highest in 13 dSm-1salinity treatment. The change in Na concentration showed
an increasing trend during15 days incubation. The concentration of Na exhibited a decreasing
trend during 60 days incubation. After 60 days Na concentration tended to be leveled off. The
changes in Na concentration were higher in non-calcareous soil than its calcareous
counterpart. The statistical analyses revealed that the effect of salinity treatment on Na
concentration was significant (p
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0
1
2
3
4
5
6
EC0 EC6.5 EC13
Salinity Treatments
Stat
e of
Agg
rega
tion
C NC
Fig. 1. Effect of salinity treatments on state of aggregation
0510152025303540
EC0 EC6.5 EC13
Salinity Treatments
Dis
pers
ion
Fact
or
C NC
Fig. 2. Effect of salinity treatments on Dispersion Factor
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6.8
77.2
7.47.6
7.88
8.28.4
8.68.8
9
0 7 15 30 60 120
Time Interval (Days)
pH
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 3. Effect of salinity treatments on Soil pH
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 7 15 30 60 120
Time Interval (Days)
EC (d
S/m
)
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 4. Effect of salinity treatments on Soil EC
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0
5
10
15
20
25
30
0 7 15 30 60 120
Time Interval (Days)
Ava
ilabl
e P
(g
g)
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 5. Effect of salinity treatments on available P
050100150200250300350400450500
0 7 15 30 60 120
Time Interval (Days)
Ava
ilabl
e S
(g
g)
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 6. Effect of salinity treatments on available S
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0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 7 15 30 60 120
Time Interval (Days)
Avai
labl
e K
Cm
ol(+
) Kg
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 7. Effect of salinity treatments on available K
051015202530354045
0 7 15 30 60 120
Time Interval (Days)
Ava
ilabl
e C
a C
mol
(+) K
g
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 8. Effect of salinity treatments on available Ca
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0
2
4
6
8
10
12
14
0 7 15 30 60 120
Time Interval (Days)
Ava
ilabl
e M
g C
mol
(+) K
g
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 9. Effect of salinity treatments on available Mg
0
1
2
3
4
5
6
7
0 7 15 30 60 120
Time Interval (Days)
Ava
ilabl
e N
a C
mol
(+) K
g
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 10. Effect of salinity treatments on available Na
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13
05101520253035404550
0 7 15 30 60 120
Time Interval (Days)
Ava
ilabl
e C
l Cm
ol(+
) Kg
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 11. Effect of salinity treatments on Cl concentration
0
5
10
15
20
25
30
35
0 7 15 30 60 120
Time Interval (Days)
Ava
ilabl
e H
CO
3 C
mol
(+) K
g
C0 C6.5 C13 NC0 NC6.5 NC13
Fig. 12. Effect of salinity treatments on HCO3-concentration
9. Discussion: Soil salinity is one of the most critical aspects that may influence the future agriculture of
Bangladesh in future. So, the short and long term effect of soil salinity need to be
investigated. In the present work short term effect of saline water application was studied.
Saline water application increased EC of the soil. As the studied soils were non-saline
addition of highly saline water (13 dSm-1) did not increase EC of soil greater than 2 dSm-1.
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This increase was greater in the later stage of incubation may be because of dissolution of
soluble salts in soil. Several investigators also reported that addition of saline water during
irrigation markedly increase soil salinity (Goorahoo et al., 2003 & Moreno et al., 2001).
Increase in soil salinity has direct positive and negative impact on soil aggregate stability.
Soil salinity associated with high exchangeable sodium percentage (ESP) and sodium
adsorption ratio (SAR) is responsible for clay swelling and dispersion (Halliwell et al. 2001
& Warrence et al., 2002). Whereas other investigators concluded that presence of dissolve
salt of Ca and Mg increase the stability of aggregates (Warrence et al., 2002). In the present
investigation increase in state of aggregation was reported. Reaction of soil and nutrient
dynamics is also affected by level of soil salinity. In the present work it was observed that pH
and EC were negatively correlated both calcareous and non-calcareous soils. Al-Busaidi and
Cookson (2003) reported that readings from the pH electrode from non-saline soils tended to
fluctuate more than when readings were taken from saline soils. However, pH readings from saline soils in different electrolytes also fluctuated but not to the same extent as in non-saline soils. Electrolytes appeared to suppress fluctuations in pH readings, probably due to, both, reducing the liquid junction effect (especially in water) and minimizing alkaline errors. The reduction in fluctuation between pH values in non-saline and saline soils supports the use of electrolytes especially in non-saline soils. However, Gupta et al. (1989) argued that sodium ions react in calcareous soils to
form sodium carbonate and bicarbonate, which by hydrolyzing at pH values more than of 8.8, leads to
a direct relationship between soil salinity and pH. Soil pH, EC has direct influence on Ca, P and S
dynamics in calcareous and non-calcareous soils. CaCO3 plays a pivotal role in P dynamics in
calcareous soil. In the present investigation P availability in soils varied with cyclic variation in Ca
availability. In calcareous soil addition of saline water increased the Ca concentration in soil solution
and thus leaded to precipitation of CaCO3 according to the theory of common ion effect. Thus Ca
concentration in soil reduced and P availability increased. But with time of incubation Ca
concentration increased. This may be due to dissolution of CaCO3. The dissolution of precipitated
CaCO3 can occur if the value of equilibrium constant of the reaction of CaCO3 precipitation is less
than 10-10 (Al-Busaidi and Cookson, 2003). This precipitation and dissolution may repeat in the
incubation period and controlled P concentration in soil. The bicarbonate ion produced during
dissolution of CaCO3 may react with Na and Mg of soil solution and thus caused to reduce bicarbonte
continuously during incubation. The initial increase in SO42- may be due to the addition of saline
water. The subsequent decrease may due to co-precipitation with CaCO3 (Al-Busaidi and Cookson,
2003). Potassium availability decreased with time in various salinity treatments in both the soils
indicates the K fixation by 2:1 type minerals and may be favored by the increase in soil moisture
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(Sparks and Huang, 1985). Although it was not observed in the present research, other scientists
reported that K decreased with increasing salinity in different soils (Bang, 2005).
10. Progress made during the period: The project work has been completed.
11. Conclusion/ Observation: The short term effect of saline water application did not increase the soil salinity greatly.
Aggregation state improved due to addition of saline water. The different nutrients behaves
quite differently in different salinity levls. The relationship between pH-EC, and precipitation
and dissolution of calcium carbonte controlled most nutrient availability in soil. Future
reseach should be directed to pH-EC relationship in calcareous and non-calcareous soil. The
role of calcium carbonte in controlling soil reactions in calcareous soils of Bangladesh not yet
well understood. The study of short and long term effect of saline water or brackish water on
soil can supply aliment to the agricutural policy makers for desiging effective irrigation
program for winter crops in forthcomming decade. A scrupolous research is essential for
finding out irrigation alternative in this field.
12. References:
Al-Busaidi, A.S., and P. Cookson. 2003. SalinitypH Relationships in Calcareous Soils. Agricultural and Marine Sciences 8(1):41-46. Bang, J. 2005. Characterization of soil spatial variability for site specific management using soil electrical conductivity and other remotely sensed data. PhD. Dissertation, Department of Soil Science, North Carolina State University, USA.
Baver, L.D. and H.F. Rhoades.1932. Soil aggregate analysis as an aid in the study of soil structure. J. Am. Soc. Agron. 24: 920-921. Fox, R.L., R.A. Olsen and H.F. Rhoades. 1964. Evaluating the sulfur status of soils by plants and soil tests. Soil. Sci. Soc. Am. Proc. 28:243-246 Gee, G.W. and J.W. Bauder. 1986. Particle size analysis. In: A. Klute (ed.) Methods of Soil Analysis. Part-1, 2nd ed. Agron.9. ASA, Madison,WI. Pp: 383-411.
Goorahoo D., S. Benes, D. Adhikari and J. Bartram. 2003. Soil characterization of fields irrigated with recycled saline drainage waters. Proceedings of the national meeting of the Irrigation Association of America (IAA). Nov. 18-20th, San Diego, CA. 12 pages.
Gupta, R.K., R.R. Singh, and I.P. Abrol. 1989. Influence of simultaneous changes in sodicity and pH on the hydraulic conductivity of an alkali soil under rice culture. Soil Science 147(1): 28-33. Halliwell, D.J., Barlow K.M. and Nash D.M. 2001. A review of the effects of wastewater sodium on soil properties and their implications for irrigation systems. Australian Journal of Soil Research. 39:1259-1267. Hunt, J. 1980. Determination of total sulfur in small amount of plant material. Analyst.
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105:83-85.
Jackson, M.L. 1973. Soil Chemical analysis. Prentice Hall of India Pvt. Ltd. New Delhi, India.
Kachinskii, N.A. 1965. Soil physics. Part-1. Publ. Visshayaskhola, Moscow.
Karim, Z., S.M. Saheed, A.B.M. Salauddin, M.K. Alam and A. Huq. 1982. Coastal saline soils and their management in Bangladesh. Soils publication no. 33, BARC.
Kaur, R. 1994. Physics of salt affected soils. In: D.L.N. Rao, N.T. Sing, R.K. Gupta and N.K. Tyagi (eds.) Salinity management for sustainable agriculture. Central Soil Salinity Research Institute, Karnal, India.
Moreno, F., F. Cabreraa, E. Fernndez-Boyb, I. F. Girna, J. E. Fernndeza and B. Bellidoc. 2001. Irrigation with saline water in the reclaimed marsh soils of south-west Spain: impact on soil properties and cotton and sugar beet crops. Agricultural Water Management :48 (2): 133-150. Murphy, J. and J.P. Riley. 1962. A modified single solution method for determination of phosphate in natural waters. Anal. Chem. Acta. 27:31-36. Warrence, N.J., J.W. Bauder and K.E. Pearson. 2002. Basics of salinity and sodicity effects on soil physical properties. Department of Land Resources and Environmental Sciences, Montanta State University-Bozeman. (can be accessed from http:\\ www. waterquality.montana.edu/docs/methane/basics.shtml, visited at 05/03/07) Olsen, S.R., C.V. Cole, F.S. Watanabe and L.A. Dean. 1954. Estimation of available P in soils by extraction with sodium bicarbonate. USDA Cir. 939 Piper, C.S. 1950. Soil and plant analysis. The University of Adelaide Press, Adelaide, Australia.
Reitemeier, R.F. 1943. Semimicroanlysis of saline soil solutions. Indus. and Engin. Chem., Analyt. Ed. 15:393-402, illus.
Rost, C.O. and C.A. Rowles. 1941. A study of factors affecting the stability of soil aggregates. Soil Sci. Soc. Am.J. 421-433. Sparks, D.L. and P.M. Huang. 1985. Physical chemistry of soil potassium. In: Potassium in agriculture soil. ASA-CSSA-SSSA, WI, USA. pp. 201-276.
SRDI, 2003. Soil Salinity in Bangladesh 2000. Soil Resources Development Institute, Dhaka.
Swarup, A. 1994. Chemistry of salt affected soils and fertility management. In: D.L.N. Rao, N.T. Sing, R.K. Gupta and N.K. Tyagi (eds.) Salinity management for sustainable agriculture. Central Soil Salinity Research Institute, Karnal, India.
USDA (United States Department of Agriculture). 2004. Soil Survey Laboratory Manual, Soil survey investigation report no. 42, version 4.0, USDA-NRCS, Nebraska, USA.
Van Bavel, C.M.M. 1949. Mean weight diameter of soil aggregates as a statistical index of aggregation. Soil Sci. Soc. Am. Proc. 14:20-23.
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Signature
(Dr. Mizanur Rahman Bhuiyan) Project Director
Counter Signature
Registrar Khulna University
Counter Signature
Registrar Khulna University
Signature
(Dr. Mizanur Rahman Bhuiyan) Project Director