A Quantitative Methodology for Estimating Soil Loss Tolerance Limits for Three States of Northern India

Soil loss tolerance limit (SLTL) is the maximum amount of soil which can be removed annually before the long-term soil productivity is adversely affected. In many situations, the establishment of a SLTL is intended to provide basic information for the maintenance of soil productivity, which becomes one of the foci of the sustainability of agricultural land use. In India a default soil loss tolerance limit of 11.2 Mg ha−1 yr −1 is followed for planning soil conservation activities. The objective of this study is to provide a methodology to estimate quantitative SLTLs for suggesting suitable soil conservation measures. The assessment framework used follows three basic steps; viz. indicator selection, indicator interpretation and integration into a soil quality (SQ) index value. A quantitative model was used to integrate potential soil indicators such as saturated hydraulic conductivity, bulk density, soil erodibility, organic carbon and pH to assess soil resistibility to erosion. Scaling functions were used to convert soil parameters to a unitless 0 to 1 scale. Normalized values of all these soil parameters were then multiplied by assigned weights based on relative importance and sensitivity analysis. Soils were grouped into 1, 2, and 3 depending on overall additive score. A general guideline developed by the USDA-Natural Resource Conservation Service (NRCS) was followed, with certain modifications in depth categories, for estimation of SLTLs. The model was tested on 14.86 Mha of land in northern India comprising of the states of Punjab, Haryana and Himachal Pradesh. SLTLs varied from 2.5 to 12.5 Mg ha−1 yr −1 compared to the single value applied earlier. Keywords: erosion tolerance limitquantitative modelplanning conservation measurePunjabHaryanaHimachal PradeshIndia ACKNOWLEDGMENT The authors are grateful to the Director at the Central Soil and Water Conservation Research and Training Institute, Dehra Dun, India, for providing encouragement in conducting the study and also to the Head of Research Centre, Chandigarh, for providing necessary facilities for carrying out the research work. The authors are also thankful to Sh. G.B. Naik and Sh. A.K.Nitant, Sh. Chait Singh and Sh.Trilok Singh for their technical support.