ABSTRACT:
Tolerable soil loss (T) is defined as the maximum rate of annual soil erosion that economically and indefinitely will continue to sustain a high level of crop productivity. Currently a T value is assigned to a soil based on its current functional state and structural integrity. However, in India a default T value of 11.2 Mg ha−1 yr−1 (5.0 t ac−1 yr−1) is being followed. Our objective is to provide adjusted T values for India's Northwest Himalayan region by incorporating bulk density, water stable aggregate measurements, infiltration rate, soil carbon, and fertility status into the assessment. A quantitative model was used to sum up overall soil performance to define the current state of soil resource. Scaling functions were used to convert soil parameters to a 0 to 1 scale. The normalized values were then multiplied by appropriate weighting factors based on relative importance and sensitivity analysis of each indicator. A categorical ranking of soil 1, 2, or 3 was given to a soil group based on the overall assessment. A general guideline developed by the USDA-Natural Resources Conservation Service (NRCS) was followed to calculate soil loss tolerance for each soil group using effective soil depth. Adjusted T values for the area ranged between 5.0 and 12.5 Mg ha−1 yr−1 (2.2 and 5.6 t ac−1 yr−1) compared to 11.2 Mg ha−1 yr−1 (5.0 t ac−1 yr−1). Use of the adjusted T values will improve conservation planning, help meet erosion control regulations for development of sustainable farm operations, and improve watershed management in this portion of India.
Footnotes
Debashis Mandal is soil scientist. Kuldip S. Dadhwal is head of Soil Science and Agronomy Division. Om Pal Singh Khola and Bihari L. Dhyani are senior scientists in agronomy and agricultural economics, respectively, at the Central Soil and Water Conservation Research and Training Institute in Dehradun, Uttaranchal, India.
- Copyright 2006 by the Soil and Water Conservation Society
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