Effect of nitrogen application and sorghum mulch on nitrogen use efficiency, microbial biomass carbon, extracellular enzymes activities and growth of mashbean (Vigna mungo (L.) Hepper)

Low nitrogen use efficiency is one of the major problems causing low yield in mashbean (Vigna mungo L.). In this study, the influence of sorghum mulch and nitrogen (N) application rates in improving the nitrogen use efficiency (NUE), soil health and performance of mashbean was evaluated. Mashbean seeds were sown with two levels of nitrogen 50 and 75 kg ha⁻¹ with sorghum mulch (@ 15 t ha⁻¹) and without sorghum mulch. The highest seedling growth, seedling dry weight, and NUE (54.5) were recorded with 75 kg ha⁻¹ N under sorghum mulch application. Application of N at 75 kg ha⁻¹ also increased the microbial biomass (MBC) (812 µg C g⁻¹) under no sorghum mulch and this trend was reverse under sorghum mulch application. The activities of extracellular enzymes increased with the increase in N application rate (from 50 to 75 kg N ha⁻¹) under both no sorghum and sorghum mulch application; however, the highest activities of β-glucosidase (1093 nM g⁻¹ h⁻¹), chitinase (4246 nM g⁻¹ h⁻¹), acid phosphatase (6698 nM g⁻¹ h⁻¹) and lucine amino peptidase (1119 nM g⁻¹ h⁻¹) were recorded under sorghum mulch application with 75 kg ha⁻¹ N. Higher N application rate (75 kg ha⁻¹) under sorghum mulch improved growth, NUE and performance of mashbean. However, application of N (75 kg ha⁻¹) improved the soil MBC under no sorghum mulch and extracellular enzymes activities under sorghum mulch application.