Agroforestry Systems of Harar, Aonla, and Soapnut: Enhancing Microbial Activity and Crop Productivity in the Sub-Tropical Region of Himachal Pradesh

This study investigated the influence of agroforestry systems involving grafted harar (Terminalia chebula), soapnut (Sapindus mukorossi), and aonla (Phyllanthus emblica) on sesame (Sesamum indicum) productivity and soil health in the sub-tropical region of Himachal Pradesh. Seven land-use treatments, including different tree–crop combinations and sole sesame cultivation, were assessed with soil sampled at 0–15 cm and 15–30 cm depths. Agroforestry systems significantly enhanced sesame growth and yield compared to sole cropping. The harar + sesame system recorded the highest benefit–cost ratio (2.36), while soapnut + sesame achieved the maximum total biomass (68.32 t ha⁻¹) and carbon stock (34.16 t ha⁻¹). Tree-based systems improved plant height, seed weight, and overall yield, with harar-based combinations showing superior performance. Soil physical properties, particularly moisture content, improved under agroforestry, especially in surface layers. Chemical attributes such as pH, electrical conductivity, organic carbon, and available N, P, and K were higher in agroforestry systems, though values declined with depth. Biological indicators, including microbial biomass carbon, nitrogen, phosphorus, and enzyme activities (phosphatase, catalase, dehydrogenase), were significantly elevated—highest under harar + sesame. Overall, agroforestry enhanced soil fertility, biological activity, and system profitability, demonstrating its potential as a sustainable strategy for improving productivity and resilience in semi-arid agroecosystems.