Residual Effect of Agroforestry Landuses on Soil Fertility

A ten-year agroforestry study was conducted on nine 15 x 90 m plots at 4% slope in the warm sub-humid climate of the Western Himalayan region of India. After 10 years the soil under crop and tree (or) hedge were collected and analyzed for its fertility level. Organic carbon content in surface soil was increased from 0.45% in cultivated fallow to 0.74%, 0.76% and 0.91% for tree + crop, Leucaena hedge + crop and sole tree cultivation respectively. Carbon, Nitrogen (C : N) ratio was very less in hedge + crop intercropping system. The total nitrogen and Olsen's phosphorus was quite high in alley cropping system when compared to sole tree cropping. Agroforestry landuse system increases the phosphorus content 2.5 times when compared to cultivated fallow land. There was not much difference in potassium content between cultivated fallow and other treatments except sole cultivation of Leucaena tree. In agroforestry cultivation, all the nutrients were decreased with increasing the depth, but in cultivated fallow the phosphorus and potassium content increased with increasing the depth. The yield of sorghum in treatment plots was increased significantly due to increased fertility level by agroforestry system.