Ecological and economical assessment of harar-soybean agroforestry system in subtropical conditions of Himachal Pradesh, India

Harar (Terminalia chebula) and soybean (Glycine max) are the potential tree and agricultural crops of subtropical region of Himachal Pradesh, India, however the potential of these crops under agroforestry system has not been explored both from ecological and economical point of view. The objective of this paper was to determine the effect of harar-soybean combination on soil chemical properties and to analyse the economics of the agroforestry system as compared to the open system. Soybean was grown under harar trees as per the recommended package of practices. Before sowing and after harvesting, soil samples were collected from four directions (East, West, North and South) at three distances (1, 2 and 3 m) from harar trees and open cropping system (sole soybean) for determining chemical properties (pH, electrical conductivity and organic carbon) and nutrient dynamics (nitrogen, phosphorus and potassium). In addition, the soil at two depths (0-15 cm and 15-30 cm) under trees at 2 m distance and in open was analyzed by GC-MS before and after cropping for the presence of allelochemicals that may affect crop yield. The economics of tree-crop combination was worked out and compared with the sole cropping system. The soil chemical properties and available nutrients in soil exhibited maximum values in the north direction. Except available phosphorus content, values of all the studied properties of soil increased with an increase in the distance of soybean crop from harar. It was also observed that values of soil chemical properties and nutrient contents increased significantly after intercropping in comparison to those before intercropping soybean. A substantial increase in soil properties was observed under the agroforestry system over the sole cropping system before sowing and after harvesting soybean. It was revealed that allelochemicals viz., octadecanoic acid, 1,2-benzenedicarboxylic acid and phthalic acid which do exist in harar trees were also detected in soil under the canopy of harar trees. The total cost of cultivation (Rs. 45,028.49 ha-1), gross returns (Rs. 101,937.78 ha-1), net returns (Rs. 56,909.29 ha-1) and benefit-cost ratio (2.26) were higher under the agroforestry system (harar + soybean) over sole soybean cropping. Improvement in soil health, soybean yield and higher economic returns indicated that combination of harar and soybean can be a viable option for farmers of subtropical areas of Himachal Pradesh for the upliftment of their socioeconomic status.