Impact of Long-Term Application of Organic Manure on Inceptisol Properties, Grain Protein Content and Yield of Wheat

A field experiment was conducted to investigate the implications of long-term farm yard manure (FYM) use on chemical and microbial properties of Inceptisol in the North-Western Plain Zone of India, and their correlation with yield and protein content of wheat grains. FYM was used at four different doses (0, 10, 20, 30 t ha−1) with recommended dose of nitrogen, phosphorus and potassium (NPK) as standard practice before sowing of both rice and wheat under rice-wheat cropping system. Application of FYM at 30 t ha−1 significantly enhanced the electrical conductivity (36.36%), nitrogen (29.79%), phosphorus (216.75%), potassium (280.15%), zinc (186.90%), copper (24.23%), organic carbon (130.77%), organic matter (132.43%), operational taxonomic units (OTUs) of top 30 bacterial classes (82.27%), genera (73.95%), plant growth promoting bacteria (PGPB, 86.00%) and lignocellulose degrading bacteria (LDB, 109.14%) over recommended NPK at p value of 0.05. Significantly high plant biomass (14.21 t ha−1) and grain yield (5.69 t ha−1) were obtained in recommended NPK treatment, followed by 30 t ha−1 FYM treatment, whereas significantly higher grain protein was obtained in 30 t ha−1 FYM treatment at p value of 0.05. The abundance of top 30 bacterial classes was highest under 30 t ha−1 FYM (100117), while lowest under recommended NPK treatment (54928). This treatment also witnessed highest presence of all beneficial bacterial classes, top 30 bacterial genera, PGPB and LDB. Highest up-regulated bacterial genes in recommended NPK, and superior soil quality parameters (nutrient profile and microbial diversity) in 30 t ha−1 FYM, indicate that sustainable yields and quality are achievable by using a balanced amount of inorganic fertilizers and organic manure.