Aonla and soybean 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 under these conditions both from ecological and economical point of view. Therefore, to promote aonla-based agroforestry system in subtropical conditions of H.P., we evaluated changes in soil properties, agricultural crop yield and the economic potential of this agroforestry system. The intercropping system was established in nine years old aonla (Phyllanthus emblica cv. NA-7) planted at 8 m x 8 m spacing intercropped with soybean (Glycine max var. Shivalik) with 45 cm x 15 cm spacing. Separate monocropping field for soybean was established adjacent to the intercropped field. The experiment was laid out in Factorial Randomized Block Design with combination of factors i.e., Direction (East, DR1; West, DR2; North, DR3 and South, DR4) and Distance from the tree trunk (1 m, D1; 2 m, D2 and 3 m, D3) as treatments (12) replicated thrice. Yield of soybean crop was recorded under agroforestry system and compared with that grown in open cropping system (sole soybean). 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 aonla trees and open cropping system. Additionally, the soil under trees at 2 m distance before and after intercropping soybean and from open system was analyzed by GC-MS to detect the presence of allelochemicals for assessing allelopathic interactions in the tree-crop system. The economic feasibility of aonla-soybean agroforestry system was determined by calculating the cost of cultivation, gross returns, net returns and benefit cost ratio. The results showed that soybean grown under agroforestry system exhibited significantly higher seed yield (6.19 q ha-1) than sole soybean (4.09 q ha-1). Soil chemical properties (pH, electrical conductivity and organic carbon) and available nutrients in soil (nitrogen, phosphorus and potassium) exhibited significantly higher values in the east direction and exhibited an increasing trend with an increase in the distance of soybean crop from aonla trees. Also, the values of soil chemical properties and nutrient contents increased significantly after intercropping soybean with aonla. GC-MS analysis of soil showed the presence of allelochemicals viz., Bis(2-ethylhexyl) phthalate; 1,2-Benzenedicarboxylic acid, bis(2-methylpropyl) ester and Dibutyl phthalate in both the land use systems. However, the remaining allelochemicals which were observed only in the agroforestry system either have been released by aonla or some other plants (weeds). Economic analysis revealed higher gross returns, net returns and benefit cost ratio for the agroforestry system than the sole cropping system. Improvement in soil health and higher economic returns indicated that combination of aonla and soybean can be a viable option for farmers of subtropical region of Himachal Pradesh which can improve their socioeconomic status.
