Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water Management Implications in Different Soils of Coastal West Bengal

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1 Int. J. Environ. Eng. Nat. Resour. Volume 1, Number 2, 2014, pp Received: May 23, 2014; Published: August 30, 2014 International Journal of Environmental Engineering and Natural Resources Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water Management Implications in Different Soils of Coastal West Bengal Shishir Raut, Buddheswar Maji and Sukanta Kumar Sarangi Central Soil Salinity Research Institute, Regional Research Station, Canning Town, West Bengal , India Corresponding author: Shishir Raut Abstract: Sorptivity was determined for soils coming under three different moisture regimes namely, irrigated cultivated (I.C.), non irrigated uplands (N.I.U.), and water logged (W.L.) from South 24 Pargana, a coastal district of West Bengal (India) for two different seasons. The study was carried out in laboratory at room temperature in plexiglass columns. Physico-chemical parameters like ph, EC, saturated moisture content, texture, organic C had also been determined. Steady state cumulative infiltration was highest (8-10 mm) in non-irrigated upland soil and lowest (1-2 mm) in water logged soil. The highest sorptivity of mmmin-1/2 was found in non-irrigated upland soil and lowest in seasonally water logged soil ( mm min-1/2). Organic C content of all soils were low (< 2%), EC values were also low (< 2 ds/m). Saturated moisture was high in water logged soil. The N.I.U. soils were having higher fraction of fulvic acid ( %) and lighter texture for which these were more capable of infiltration, where as W.L. soils having greater fraction of insoluble humic acid ( %) and exhibited less cumulative infiltration. Sorptivity decreased as the clay content, ph, EC, porosity and humic acid content of the soil increased (r values are -0.79, -0.75, -0.75, and -0.85, respectively). Both the percentage of clay content and percentage of clay plus silt were significantly (+ve) correlated with the percentage of organic carbon (r 2 = 0.76 and 0.70, respectively). The correction of soil ph and EC, and modification of soil texture with adoption of appropriate amendments will help in improving sorptivity of the Irrigated cultivated and water logged soils. Key words: Infiltration, soil sorptivity, humic acid, fulvic acid. 1. Introduction Sorptivity is defined as the ability of a soil to absorb water during infiltration. Theoretically, Philip [1] has established that, in absence of gravity effect, the amount of water absorbed during infiltration is proportional to the square root of time (t) when water is allowed to infiltrate into a horizontal column of porous material the surface of which is maintained at a constant moisture content i.e., I = St ½ where S is a constant and is called sorptivity, I is cumulative infiltration. Sorptivity, S= (θ o -θ i )(D/π) 1/2, where D is weighted mean diffusivity, θ i is initial soil water content, θ o is saturated wetness and t is time. Sorptivity is defined only in relation to a fixed initial state θ i and an imposed boundary condition θ o.this is true for t > 0. Typical values of the steady infiltration rate for sandy and silty soils, loams and clayey soils are mm/h, 5-10 mm/h and 1-5 mm/h respectively [2]. The in situ measurement of sorptivity with infiltrometers using the falling head method is the fundamentals in soil physics. The dependence of sorptivity and conductivity on density variations is about 5%. There were good agreement between the S estimation method and the classical Philip method for horizontal infiltration at non ponding condition. Study conducted by Harden and Scruggs [3] showed that in the lower slopes of Andes (Equador) infiltration rates ranged from 6 to 206 mm /h, 16 to 117 mm /h in the

2 78 Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water southern Appalachians and mm /h in Luquillo Mountains (Puerto Rico) at forested sites. Soils under sal forest, chrysopogon and cropland have less water drop penetration time and therefore are classified as wettable. However soils under eucalyptus plantation and panicum stand showed considerable hydrophobicity. This is considered as being caused by differences in organic matter composition rather than amount of organic carbon [4]. Soils containing a large amount of hydrophobic materials such as plant litter, residue and microbial by-products may become water repellent or less wettable [5]. These are generally thought to be present as a coating on soil particles or aggregates. The accumulation of hydrophobic waxes on soil particles humic acid and/or fulvic acid soil coatings and other long-chained organic compounds on or between soil particles are all accepted as factors contributing to this negative impact phenomenon [6]. Wettability of soil is greatly influenced by nature of decomposed organic materials [7]. Topography and rainfall are the main factors which determine a soil would be water logged or not. Information on the influence of different fractions of organic material such as humic acid, fulvic acid and humin on soil wettability/repellency resulting in water logging is meagre. The study of the relationship between sorptivities and humic acid in Coastal West Bengal soils is also meagre. Therefore present investigation was carried out to study the effect of three different water regimes on soil sorptivities and on the composition of soil organic matter and to study the effect of different fractions of organic matter towards water repellency/soil wettability. 2. Materials and Methods Soil samples were collected for two different seasons from two different depths (0-15, and cm) from Sonakhali village of Coastal West Bengal coming under three different moisture regimes namely non-irrigated upland (N.I.U.; extreme north), irrigated cultivated (I.C.; extreme south of the study area), and seasonally water logged (W.L.; middle; Fig. 1). Soils were classified as Aeric Endoaquepts and Typic Fluvaquents. It covers approximately ten sq km area. The seasons for collections were Jan-Feb., 2012 (before rice cultivation) and May-June, 2013 (after rice cultivation). The area is mostly mono cropped (rice cultivated). Soil samples were collected from three different points (three replications) under each moisture regimes (Fig. 1). The horizontal infiltration and sorptivities were studied in plexiglass columns in the laboratory. The columns were prepared placing plexiglas segments (0.01 m height and 32 in number) one over another. These were filled as uniformly as possible with soil sample at bulk density of 1.3 Mg m -3. Columns were placed horizontally on a wooden stand and water was introduced to the inlet end from marriotte tube at a constant suction of 0.2 k Pa. Water entering the column was measured volumetrically and the distance from the water source to wetting front was visually observed. After completion of the infiltration, the columns were sectioned into one cm segments and water content was determined gravimetrically. From these, soil water diffusivity, D (θ) was calculated by using the following formula: D (θ ) = -1 /2t. dx/ dθ ʃ xdθ (1) where, t is time; x is distance; the definite integral is solved between initial wetness (θ i ) and final wetness (θ). The weighted mean diffusivity was calculated according to Crank s [8] formula: D = 1.66/ (θ o -θ i ) 5/3 ʃ D(θ) (θ o -θ i ) 2/3 dθ (2) where D is weighted mean diffusivity, θ i is initial moisture content, θ o is saturated moisture content D(θ) is soil water diffusivity. Physicochemical parameters like soil texture, ph, EC, organic C etc. were also studied. Cumulative infiltration was plotted as a function of time (Fig. 2).

3 Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water 79 The physicochemical characteristics of the soils were determined by using Black [9] and Jackson [10] methods. Particle size analysis was done using a Buoycous hydrometer. Organic carbon was determined by Walkley and Black method, ph and electrical conductivity (E:C) were measured in 1: 2 soil : water ratio. Saturated water content of the soils was determined by using Keen s box [11]. The humic acid and fulvic acid fractions of organic matter were separated by following the procedures of Kononova [12]. Relationship between sorptivity and other soil parameters were also determined. Correlation between clay and EC, clay and organic carbon as well as clay plus silt and organic carbon for the soils was studied. 3. Results and Discussions 3.1 Physicochemical Properties and Soil Sorptivities The highest steady state cumulative infiltration was observed in N.I.U. soil (6-10 mm) followed by irrigated cultivated (I.C.) soil (6-8 mm) and seasonally water logged (W.L.) soil (1-2 mm). This result can be verified from the slope of the cumulative infiltration and time curves (Fig. 2). In 50 minutes time only 1-2 mm water infiltrated in W.L. soil. Where as for the same period 4-7 mm water infiltrated in N.I.U. soil. Infiltration in I.C. soil was medium (4-5 mm). Irrigated cultivated (I.C.) and water logged (W.L.) soils were clay, with a clay content of 44-64% in the Fig. 1 The study area and sample locations (NIU: Non-irrigated uplands, WL: Water logged, IC: Irrigated Cultivated).

4 80 Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water Cumulative infiltration (mm) nd season NIU IC WL Time (min) Fig. 2 Cumulative infiltration as a function of time for soils of three moisture regimes. surface layer (Tables 1-2). Clay content in non irrigated upland soil (N.I.U.) was around 40% and were clay loam. In the 15-30cm soil layer for I.C. and W.L. soils clay content did not differ much (36-64%, clayey). All three soils were low in organic matter content (< 2%). The highest porosity or saturation water content was found in W.L. soil ( cm 3 cm -3 ) and lowest was in N.I.U. ( cm 3 cm -3 ). The N.I.U. and W.L. surface soils were slightly acidic to neutral (ph ). The E.C. values of all soils were low for all depths ( ds/m; Tables 1-2). Water content of air dried soil before initiation of infiltration ( i ), final water content ( 0 ) and water gain during infiltration ( 0- i ) are presented in Tables 3-4. Average water content in soils after infiltration varied from cm 3 cm -3 in I.C. and cm 3 cm -3 in W.L. soils, whereas values were cm 3 cm -3 in NIU soils. The gains were higher in I.C. and W.L. soils. Highest sorptivity ( mmmin -1/2 ) was observed in N.I.U. soil, followed by mmmin -1/2 in I.C. soil and mmmin -1/2 in W.L. soils. Sorptivity values differ significantly (F tab (2,6) > F cal ) for two different moisture regimes for different depths. These results can also be verified from the slope of the cumulative infiltration vs. t ½ relationship curves (Fig. 3). The slope of N.I.U. soils in the present study were higher than the irrigated cultivated and water logged soils. The seasonal variation of cumulative infiltration may be associated with the cultivation practices i.e., root Cumulative infiltration (mm) NIU Square root of min IC WL Fig. 3 Cumulative infiltration as a function of square root of time. activity apart from the variations due to soil texture [13]. In the present study the seasonal variation of cumulative infiltration in different soils was low (Fig. 2). However, soil samples collected from the 2 nd season showed highest cumulative infiltration as compare to those collected in the 1 st season. During rice cultivation all these soils were puddled. High clay content facilitates puddling resulting in the decrease in non-capillary pore spaces which in turn decreases infiltration in the present study in case of irrigated cultivated and water logged soils (Fig. 2). In our study the cumulative infiltration of non-irrigated upland soils was about 5 times higher than that of water logged soils. This result is in agreement of the experimental results of Singh and Bhargava [14]. Organic C content of coarse soils are usually lower than clayey soils [15] for all depths. In the present study for all water regimes organic carbon percentages decreased with soil depths (Tables 1-2) and organic carbon content of N.I.U. soils ( %) were less than that of I.C. ( %) and W.L. ( %) soils. The relatively high porosity value of cm layer of N.I.U. as compared to the surface soil was associated with more clay content (Tables 1-2). Similarly, the high porosity of W.L. and I.C. soils were associated with high % of clay for all the three layers. E.C. values for all three soils were low, which increased slightly with soil depth. This might be associated with more compaction with increased soil

5 Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water 81 depth. Sorptivity values differ significantly (F tab (2,6) > F cal ) for three different moisture regimes for different depths (Tables 3-4). The sorptivity values of sandy loam soil, clay loam and clay soils were 6.9, 3.3 and 1.9 mm min -1/2 studied in Inceptisol soils of Gujarat (India) [16]. The vertical sorptivity studied in India was 2.2 cm min -1/2 in Eucaluptus stand and 3.2 cm min -1/2 under cropland [17]. Sorptivity in the present Table 1 Name of soil Physicochemical characteristics of Sonakhali soil (1 st season). Particle size (%) S Si C Tex class Org C (%) ph EC (ds/m) s (cm 3 cm -3 ) (0-15cm) NIU cl IC C WL C (15-30 cm) NIU cl IC C WL C S: sand, C: clay, and l: loam; NIU: non-irrigated upland, IC: irrigated cultivated, WL: water logged. Table 2 Physicochemical characteristics of Sonakhali soil (2 nd season). Name of soil Particle size (%) S Si C Tex class Org C (%) ph EC (ds/m) s (cm 3 cm -3 ) (0-15cm) NIU cl IC C WL C (15-30cm) NIU cl IC C WL C S: sand, C: clay, and l: loam; NIU: non-irrigated upland, IC: irrigated cultivated, WL: water logged. Table 3 Water content of soil samples, gain in water content and sorptivity (1 st season). Name of soil i (cm 3 cm -3 ) 0 (cm 3 cm -3 ) 0- i (cm 3 cm -3 ) Sorptivity (mmmin -1/2 ) (0-15cm) NIU IC WL (15-30cm) NIU IC WL F 2, 6 > F tab(1%) ; C.D. =2.7; T1 = 11.9, T2 = 7.0, T3 = 4.0. Table 4 Water content of soil samples, gain in water content and sorptivity (2 nd season). Name of soil i (cm 3 cm -3 ) 0 (cm 3 cm -3 ) 0- i (cm 3 cm -3 ) Sorptivity (mmmin -1/2 ) (0-15cm) NIU IC WL (15-30cm) NIU IC WL F 2, 6 > F tab(1%) ; C.D. =2.8; T1 = 12.4, T2 = 6.2, T3 = 3.5.

6 82 Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water study is affected by tillage intensity and applied irrigation water. Sorptivity in the fields with more number of irrigation (I.C. fields) was 14-53% higher than less number of irrigated plots (W.L. fields). Irrigation increases total porosity and pore continuity. For this reason, sorptivity of irrigated cultivated fields in the present study might have been higher than that of the W.L. fields, though the textural classes of both types of fields were similar [18]. 3.2 Humic Substances The humic acid (H.A.) and fulvic acid (F.A.) fractions of organic matter in the present study were separated by Kononova method and are given in Table 5. Fractionation of organic matter showed that % of H.A. was highest (0.32%) in W.L. soil and % of F.A. was lowest (0.08%) in the surface layer of the same soil. On the other hand, the F.A. fraction was highest in N.I.U. soil (0.2%). I.C. soils showed intermediate values (0.10%). In the lower layers also H.A.% was higher in the W.L. soils (0.30). The H.A./F.A. ratio decreased with depth (0.5 to 0.44 for N.I.U. and 4.3 to 4.0 for W.L. soils). The relationships between sorptivity and clay, ph, E.C., porosity and humic acid were significant (at 1% probability level) (r = -0.79, -0.75, -0.75, and respectively), exponential and negative (Table 6). Percentage fulvic acid was positively correlated (r = 0.90, significant at 1% level) with sorptivity. Table 7 shows that both the percentage of clay content and percentage of clay plus silt were significantly (+ve) correlated with the percentage of organic carbon (r 2 = 0.75 and 0.72 respectively). Humus is the major soil organic matter component making up 75-80% of the total. The humus content in alluvial soil is 1.5-6% [19]. The humic acid fulvic acid ratio in the present study was in the surface layers of N.I.U. and for I.C. and W.L. soils which decreased with soil depth [20]. Presence of humic acid in soil generally decreases volumetric water content of soil. Decline in water repellency of soil is due to the presence of water soluble fulvic acid. The N.I.U. soils in the present study were having higher fraction of fulvic acid ( %) for which these were more capable of infiltration, where as W.L. soils having greater fraction of insoluble humic acid ( %) and exhibited less cumulative infiltration [21] (Table 5). Regression equations in Table 8 showed that sorptivity Table 5 Humic acid and fulvic acid content of Sonakhali soil (pooled data for two seasons). Soils Total organic H.A. F.A. H.A./F.A. matter (%) (%) (%) ratio (0-15 cm) 0.68 N.I.U I.C W.L (15-30 cm) 0.61 N.I.U I.C W.L I.C.: irrigated cultivated, W.L.: water logged, N.I.U.: non irrigated upland. Table 6 Relation between sorptivity (S) and other parameters (x) of soil. Soil parameter (x) Correlation Regression coefficient ( r) equation % clay ** S = 5.9 e x ph * S = 358 e x EC (ds / m) ** S = 18.5 e x Porosity (cm 3 cm -3 ) (saturated water ** S = 30 e -4.5-x content) Humic acid (%) ** S = 5 e -1.7-x Fulvic acid (%) 0.90 ** S = 0.45 e 12.3-x * significant at 5% probability level, ** significant at 1% probability level, S is sorptivity (mm min -1/2 ). Table 7 Relation between % clay, % silt + clay and organic carbon. Soil separates (X) Square of correlation coefficient ( r 2 ) Regression equation % clay 0.75* Y = X % clay + silt 0.72* Y = X * significant at 5% probability level, Y is soil organic carbon (%). Table 8 Correlation matrix generated for EC and clay content of soil. Parameters Clay (%) EC (1:2)(0-0.15m) 0.46 EC ( m) 0.50

7 Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water 83 decreased as the clay content, ph, EC, porosity and humic acid content of the soil increased (r values are -0.79, -0.75, -0.75, & -0.85, respectively). These were in agreement with the findings of Singh and Kundu [22] for Orissa soils. The % of clay content was found to be the best predictor of organic carbon. Table 7 showed that both the percentage of clay content and percentage of clay plus silt were significantly (+ve) correlated with the percentage of organic carbon (r 2 = 0.75 and 0.72 respectively). This may be attributed to the decrease in C mineralization with increase in finer sized particles. Or in other words, pores of smaller sizes protect organic substrates against microbial decomposition in soils [23]. The correlation matrix of soil texture and EC values shows that EC values were positively correlated (r = 0.46) with clay and EC values of higher depth are also positively correlated with clay (r = 0.50) (Table 8). 4. Conclusions Cumulative infiltration and sorptivity studied in plexiglass columns in laboratory showed that in general the values were high in N.I.U. soils (= mmmin -1/2 ) and low in water logged soils (= mmmin -1/2 ) ; and intermediate in irrigated cultivated soils (= mmmin -1/2 ). Presence of humic acid in soil generally decreases volumetric water content of soil. Decline in water repellency of soil is due to the presence of water soluble fulvic acid. The N.I.U. soils in the present study were having higher fraction of fulvic acid ( %) for which these were more capable of infiltration, where as W.L. soils having greater fraction of insoluble humic acid ( %) and exhibited less cumulative infiltration [24]. The humic acid fulvic acid ratio in the present study decreased with soil depth. Presence of humic acid in soil generally decreases volumetric water content of soil which might have contributed to create water logging on the surface. In soils where cumulative infiltration and sorptivity are low (W.L.) to intermediate (I.C.) (middle and lower part of Fig. 1), adoption of suitable management practices such as deep ploughing, addition of sand and vertical drainage for in situ conservation of water is necessary to improve water use efficiency and productivity of the soils. Physico-chemical parameters like Organic carbon, porosity, EC, ph etc. and sorptivities studied in two different seasons did not differ much indicating the influence of seasons on soil sorptivity was low. However, the correction of soil ph and EC, and modification of soil texture with adoption of appropriate amendments will help in improving sorptivity of the soils. Addition of organic matter in the N.I.U. soil (top of Fig. 1) is needed to improve organic carbon status of soil and to improve water holding capacity of soil. Acknowledgment Authors acknowledge Director, CSSRI for his help and support during doing the research. References [1] J.R. Philip, Study of water infiltration in the soil under different tillage practices, Soil Science 83 (1957) 345. [2] M.M. Kononova, T.Z. Nowakowski, G.A. Greenwood, Soil Organic Matter-Its Nature, Its Role in Soil Formation and in Soil Fertility, Pergaman Press, Oxford, 1961, p [3] C.P. Harden, P.D. Scruggs, Infiltration on mountain slopes: A comparison of three environments, Geomorphology 55 (2003) [4] C.S. Piper, in: Soil and Plant Analysis, Academic Press, New York, [5] S.H. Doerr, R.A. Shakesby, R.P.D. Walsh, Soil hydrophobicity variations with depth and particle size fraction in burned and unburned Eucalyptus globules and Pinus Pinaster forest terrain in the Agueda basin, Portugal Catena 27 (1996) [6] C.M.M. Franco, P.J. Clarke, M.E. Tate, J.M. Oades, Hydrophobic properties and chemical characterizartion of natural water repellent materials in Australian sands, Journal of Hydrology 231 (2000) [7] Y.L. Zinn, Rattan Lal, D.V.S. Resck, Texture and organic carbon relations described by a profile pedotransfer function for Brazilian Cerrado soils, Geoderma 127 (2005) [8] J. Crank, in: The Mathematics of Diffusion, Oxford University Press, London and New York, 1956.

8 84 Effect of Water Regimes on Soil Sorptivity and Nature of Organic Matter and Water [9] C.A. Black, Methods of soil analysis, part I, Agronomy Monograph no. 9, American Society of Agronomy, USA, [10] M.L. Jackson, in: Soil Chemical Analysis, Prentice Hall of India Pvt. Ltd., New Delhi, [11] R. Singh, D.K. Kundu, Sorptivity of somesoils in relation to their physicochemical properties, Journal of the Indian Society of Soil Science 49 (2001) [12] M.M. Kononova, in: Soil Organic Matter, Pergaman Press, Oxford, 1966, pp [13] B.P. Ghildayal, R.P. Tripathy, in: Soil Physics, Wiley Eastern Ltd., New Delhi, 1987, pp [14] R. Singh, G.P. Bhargava, Infiltration Characteristics of some Inceptisols, Journal of the Indian Society of Soil Science 41 (1993) [15] F. Mtambanengwe, P. Mapfumo. H. Kirchmann, Decomposition of organic matter in soil as influenced by texture and pore size distribution World, Journal of Microbiology 20 (2008) [16] R.R. Weil, Humic/fulvic acid ratios of some surface soils, American Journal of Alternative Agriculture 8 (1993) [17] Shishir Raut, H. Chakraborty, Influence of water regimes on soil sorptivity and nature and availability of organic matter in Inceptisol, Journal of Agrcultural Physics 8 (2008) [18] R. Bhattacharya, S. Kundu, S.C. Pandey, K.P. Singh, H.S. Gupta, Tillage and irrigation effects on crop yields and soil properties under the rice-wheat system in the Indian Himalayas, Agricultural Water Management 95 (2008) [19] D. Mandal, J. Jayaprakash, Water repellency of soils in the lower Himalayan regions of India: impact of land use, Current Science 96 (2009) [20] F.J. Stevenson, in: C.A. Black (Ed.), Methods of Soil Analysis, Pat I, American Society of Agronomy, Madison, Wisconsin, USA, [21] B.P. Ghildayal, R.P. Tripathy, in: Soil Physics, Wiley Eastern Ltd., New Delhi, 1987, pp [22] R. Singh, D.K. Kundu, Sorptivity of some soils in relation to their physicochemical properties, Journal of the Indian Society of Soil Science 49 (2001) [23] R.R. Weil, Humic/fulvic acid ratios of some surface soils American, Journal of Alternative Agriculture 8 (1993) [24] A.V. Dyke, P.G. Johnson, P.R. Grossl, Humic substances effect on moisture retention, nutrition, and colour of Intermountain West Putting Greens USGA, Turfgrass and Environmental Research Online 8 (2009) 1-9.