Agropedology 2018, 28 (02), 118-136 Soil Erosion and Crop Productivity Loss in Palghar and Thane Districts of Maharashtra S. V. Shejale*, S. B. Nandgude, S. S. Salunkhe, M. A. Phadtare and D. M. Mahale Department of Soil and Water Conservation Engineering, College of Agricultural Engineering and Technology, Dr. B.S.K.K.V., Dapoli- 415 712, Maharashtra, India Abstract: Present research work was carried out on soil erosion and crop productivity loss in Palghar and Thane districts. The study also describes tolerable soil loss and relationship between top-soil loss and yield loss. The estimated average annual soil loss was 40.45 t ha-1yr-1 before adoption of the soil and water conservation measures (by USLE method) and estimated average tolerable soil loss was 9.36 t ha- 1yr-1, for Palghar district. Similarly, the estimated average annual soil loss and tolerable soil loss were found to be 35.89 t ha-1yr-1 and 9.61 t ha-1yr-1, respectively for Thane district. The estimated average conservation practice factor (P) factors were obtained as 0.32 for Palghar district and 0.30 for Thane district to bring the soil loss below the tolerable limit. After adoption of soil and water conservation measures, the estimated soil loss were 9.02 t ha-1yr-1and 9.38 t ha-1yr-1 for Palghar and Thane districts, respectively. Keywords: Soil erosion, USLE, tolerable soil loss, RS and GIS. Introduction expensive process. A number of parametric models have been developed to forecast soil erosion. Universal Soil Soil is one of the limited and irreplaceable Loss Equation i.e. USLE (Wischmeier and Smith 1978) resource natural resource and provides beneficial is the most popular empirically based model used nutrients, water and support to plants. Soil erosion is globally for erosion prediction. However, estimation of major global issue specifically for developing countries soil loss needs to be coupled with soil formation process like India. Hence, soil erosion and consequently land through pedogenesis. So overall soil erosion and related degradation are the major threats to Indian food security productivity loss of land is a complex phenomenon and Maharashtra state is not an exception. The quantity involving soil erosion, soil formation, input applications of soil erosion per year in Maharashtra is 773.5 M tonnes and environmental conditions. It demands and 94 per cent of that erosion is water induced. multidisciplinary study of all aspects to get realistic view Assessment of soil erosion is long-term and of relationship between soil loss and crop productivity. For developing suitable soil conservation strategies, knowledge of the prevailing and permissible *Corresponding author: (Email: [email protected]) Soil erosion and crop productivity 119 rates of soil erosion is an essential pre-requisite. of 2,578 mm while it is 4, 225.10 sq. km. (TGA) for Tolerable soil loss is a concept developed in the 20th Thane district having average annual rainfall of 2,584 century and it is useful to judge if a soil has potential risk mm. of erosion, productivity loss and off-site damages. The acceptable rate of soil erosion (T-value) is defined as the Data Collection maximum amount of erosion at which the quality of a Tehsil-wise daily rainfall data of Palghar and soil as a medium for plant growth can be maintained. Thane districts for 1998-2016 were obtained from Quantifying the acceptable soil loss without affecting Department of Agriculture, Maharashtra State. The crop productivity is a major challenge for researchers, major soils of the study area are low activity clay soils planners, conservationists and environmentalists. If the mostly derived from laterite. The different soil erosion exceeds the value, it adversely affects parameters such as sand, silt, clay and organic carbon productivity and must be brought down within the were collected from the secondary sources (Thawakar permissible rate to ensure sustainability of a production 2014). Shuttle Radar Topographic Mission (SRTM) data system. Conservation objectives for soil loss tolerance was used and Land use/ Land cover was prepared using are based on maintaining a suitable seedbed and nutrient LANDSAT-8 (Date-19/03/2017, winter). Crop data supply in the surface soil, maintaining adequate depth were collected from the District Superintending and quality of the root zone, and minimizing Agriculture Office (DSAO) of Palghar and Thane unfavourable changes in water availability throughout districts respectively to obtain the crop cover the soil. This kind of study is very essential in Konkan management factor (C). The bulk densities of different region of Maharashtra due to extreme weather location for all tehsils falling in study area were conditions and huge loss of soil through run-off. Palghar computed by using pedo-transfer function (PTF) (Kaur and Thane are coastal districts of Maharashtra et al. 2002). surrounded by the Arabian Sea in the west and the Sahyadri Mountains in the east. Due to high rainfall and Soil Erosion Model- USLE hilly terrain both district are facing problem of erosion. However, due to hilly terrain of Sahyadri ranges, data The Universal Soil Loss Equation (Wischmeier availability or accessibility is scare. The application of and Smith 1978) is being used widely, both within the Remote Sensing (RS) and Geographical Information US and internationally for assessment of soil loss. The System (GIS) is the most suitable technique for coastal equation given by Wischmeier and Smith (1978) is, resource management. GIS based analysis gives better results and effective strategies for the mitigation of such A = R*K*L*S*C*P .... (1) affected coastal zones. where, A is computed soil loss (t ha-1yr-1), R is Materials and Methods rainfall erosivity factor (MJ mm ha-1 h-1yr-1), K is soil Study area erodibility factor (t-ha-hr ha-1MJ-1mm-1), L is slope length factor, S is slope steepness factor (%), C is cover- Palghar and Thane districts were selected as management factor and P is supporting practices factor. study area. Palghar district is situated between 19° 17' N and 20° 14' N latitude and 72° 39' E and 72° 31' E Rainfall Erosivity Factor (R) longitude. Thane district is situated between 19°19' N and 19° 23' N latitude and 73° 19' E and 73° 30' E Rainfall erosivity refers to the ability of rainfall longitude. The total geographical area of Palghar district to erode the soil particles from an unprotected field. In is 5,328.3 sq. km. associated with average annual rainfall present study, tehsil-wise daily rainfall data was used for 120 S. V. Shejale et al. estimating erosivity index. Rainfall intensity data was Where, L = Slope length in meters and Sp = not available for study area and hence the daily Slope steepness in percentage. Using this equation, the precipitation and EI30 data of Wakawali station were used map of slope length was prepared. for regression analysis (Yadav and Mhatre 2005). The Although L and S factors were determined following equation implies the correlation between daily separately, the procedure has been further simplified by erosivity index and daily rainfall. combining the L and S factors together and considering the two as a single topographic factor (LS) (Wischmeier Y = 0.3339x1.50 …. (2) and Smith 1965). The LS factor layer was generated for, I. Slope steepness less up to 21 %, the equation modified where, Y is daily erosivity index and x is daily by Wischmeier and Smith (1978) was used which is, precipitation. The equation was power in nature and LS1= (L / 22.13)m *(65.41 sin2è+ 4.56 sin è + 0.065) the coefficient of determination obtained was 0.7624. …. (5) where, LS1 is the slope length and gradient Soil Erodibility Factor (K) factor and è is angle of the slope. II. Slope steepness of 21 % or more, the equation used, Soil erodibility is the vulnerability or which is given by susceptibility of the soil to get eroded. An algebraic LS2= (L / 22.13)0.7 * (6.432 * sin (è 0.79) *cos (è)) approximation of the nomograph that includes soil .… (6) parameters such as texture, structure, permeability and where, LS2 is the slope length and gradient organic matter content is proposed by Wischmeier and factor, è is angle of the slope and L is slope length in Smith (1978) and Renard et al. (1997). metre. The slope maps (both in per cent and degree ) were prepared from the SRTM DEM. Based on these -4 1.14 K= {[2.1*10 M (12-a) + 3.25 (b-2) + 2.5 (c- slope maps, slope length (L) and slope gradient (S) maps 3)]/100}*0.1317 …. (3) and finally a layer of LS factor were generated for Palghar and Thane districts. Where, K is soil erodibility factor (t-ha-hr ha-1MJ-1mm-1), M is [(% silt + 0.7 * % sand) * (100 - % Crop Management Factor (C) clay)], a is organic matter content, b is structure of the soil and c is permeability of the soil. Crop management factor is the ratio of soil loss Based on soil parameters, tehsil-wise Soil from a cropped land under specific condition to soil loss erodibility factor (K) factor values for different locations from a continuous fallow land, provided that soil type, of the study area were calculated by using Eqn. 3. slope and rainfall conditions are identical. LANDSAT-8 data were used to find out the various land use classes. Topographic Factor (LS) Weighed value of C based, on cropping pattern, was calculated for different classes and C factor was Topographic factor (LS) in USLE accounts for prepared. the effect of topography on sheet and rill erosion. The two parameters that constitute the topographic factor are Conservation Practice Factor (P) slope gradient (S) and slope length factor (L) and can be estimated from a digital elevation model (DEM).