Enhancing soil microbial health: synergistic effects of long-term manuring and nitrogen fertilization on microbial dynamics in semiarid agroecosystems

The soil’s biological health is an important aspect in sustaining crop production in arable soils. The impact of the long-term application of graded doses of farmyard manure(FYM) and its integration with mineral nitrogen on soil biochemical properties was investigated in a pearl millet-wheat system. The study involved four levels of FYM (0, 10, 20 and 30 Mg ha-1) and two nitrogen levels (0 and 120 kg ha-1) and the effects were assessed soil nitrogen availability, microbial activity and nitrogen (N) cycling soil enzymes activities in two soil depths (0-15 and 15-30 cm). The results showed a significant increase (p< 0.05) in soil available nitrogen with addition of FYM and N and it ranged from 169-328 kg ha-1 in surface soil and 132-238 kg ha-1 in subsurface soil. The soil microbial biomass carbon (MBC) and nitrogen (MBN) content was significantly increased with increasing FYM and N levels, where MBC ranging from 162-1189 mg g-1 soil in 0-15 cm depth and 91-852 mg g-1 soil in 15-30 cm depth. The substrate-induced respiration (SIR) and soil microbial quotient (SMQ) was also reported with FYM and N application irrespective of soil depths. The soil urease activity was increased by 227% in surface soil and 323% in subsurface soil with increased FYM level from 0 to 30 Mg ha-1. The activity of arginine deaminase in soil ranged from 4.36-10.3 µg NH4+ g-1 soil hr-1and 2.60to 6.34 µg NH4+ g-1 soil hr-1in 0-15 cm and 15-30cmsoil layer, respectively. Thus, the study emphasizes the importance ofFYM and N fertilization for enhancing soil microbial biomass,activity and nitrogen availability in semiarid environment, all of which support better soil health and sustainable crop production.