Maize response to soil properties improved with beneficial microbes, humic acid and farmyard manure application

To avoid environmental pollution, the useful and safe disposal of farmyard manure (FYM) was assessed during a two-year (2017 and 2018) field experiment using beneficial microbes (BM): 25 and 50 L ha-1, humic acid (HA): 3, 6 and 9 kg ha-1, and FYM: 10, 15 and 20 Mg ha-1 compared with a control (without BM, HA or FYM). Doubling the amount of BM from 25 to 50 L ha-1 delayed phenological events of maize (Zea mays L.) by one day, decreased soil total nitrogen (Ntot) content (12.6%) but improved soil bulk density (BD) (1.25 Mg m -3), electrical conductivity (EC) (1.90 dS m-1) and mineral N (Nmin) content (33.89 mg kg -1 soil). Increasing HA application from 3 to 9 kg ha-1, physiological maturity of maize delayed by 2 days but increased soil EC (0.11 dS m-1), BD (1.63%), Nmin (12.94%) and decreased soil Ntot (34.42%) content. With the FYM level increasing from 10 to 20 Mg ha -1, the phenological events were delayed, but soil properties, i.e., pH (−0.3 unit), EC (6.66%), BD (−5.83%), Nmin (28.14%) and Ntot (30.16%) content, were improved. Soil properties like EC and Ntot and Nmin contents showed significant positive correlation with maize leaf area, grain N content and grain yield. It was concluded that with addition of either 50 L ha-1 BM or 6–9 kg ha-1 HA, FYM mineralization increased, growth periods prolonged and soil fertility indices improved. Thus, for improving the Nmin availability and prolonged maize phenological duration for maximizing productivity, 20 Mg ha-1 FYM should be applied in combination with 50 L ha-1 BM and/or 6 kg ha-1 HA.