Enhancing Soil Biological Indices under Direct-Seeded Rice through Integrated Nutrient Management

Intensive chemical fertilization in the rice-wheat system of the Indo-Gangetic Plains as adversely affected soil biological resilience. The present study (Kharif 2024) evaluated the effect of integrated nutrient management (INM) involving green manures and graded nitrogen levels on soil biological properties under direct-seeded rice (DSR) in an Inceptisols of Northern India. The experiment was conducted at the College of Agriculture (Kaul) of CCS Haryana Agricultural University, Hisar laid out in Randomized Block Design with nine treatments involving combinations of two green manure crops (Sesbania aculeata and Vigna radiata) and varying levels of the recommended dose of nitrogen (RDN) i.e T1 (control), T2 (Dhaincha), T3 (Mungbean), T4 (50% RDN + Dhaincha), T5 (50% RDN+ Mungbean), T6 (75% RDN), T7 (75% RDN + Dhaincha), T8 (75% RDN + Mungbean) and T9 (100% RDN). Soil biological parameters including Urease, Alkaline Phosphatase (APA), Dehydrogenase (DHA), and Microbial Biomass Carbon (MBC) and Nitrogen (MBN) were assessed before sowing and after harvest. Results revealed significant improvement in all biological indices under integrated treatments compared to control. The treatment receiving 75% RDN + Dhaincha recorded the highest enhancement in MBC, MBN, urease, alkaline phosphatase, and dehydrogenase activities. The findings indicate that partial substitution of mineral nitrogen with leguminous green manure strengthens soil biological functioning and improves nutrient cycling under aerobic rice systems.