ORGANIC AND MINERAL FERTILIZERS SWAY THE NITROGEN AVAILABILITY TO PLANTS VIA MICROBIAL DIVERSITY - A LONG-TERM IMPACT

Continued application of organic matter and inorganic synthetic fertilizers to soil influences the nutrient dynamics and diversity of microbial communities. A single site field study (plot size of 9.5 m x 5 m used in each treatment) encompassing 23 years compared the impact of organic and NPK fertilizers for exploring amino acids as indicators of nitrogen fate, and phospholipid fatty acids (PLFA) as biomarkers of microbial diversity in North China Plain field. Treatments in quadruplicated RCBD experiment were: whole N from organic manure (OM); half N from OM + half N from chemical fertilizer (HOM); chemical NPK fertilizers (NPK), NP, NK, PK, and no fertilizer control or check (CK) applied to raise wheat and maize crops continuously. To each crop, N was applied at the rate of 150 kg N ha(-1) through organic manure and/or chemical fertilizer urea in two splits (90 + 60 kg N ha(-1)). Calcium superphosphate (150 kg P2O5 ha(-1)) and potassium sulfate (150 kg K2O ha(-1)) were applied basally in respective treatments. Soil samples were drawn from each treatment after 23 years of experimentation. These fertilization amendments exhibited that contents of total nitrogen and amino acids were significantly (p <= 0.05) higher under OM and HOM compared to NPK and CK treatments. Total amino acids determination revealed that N and P included treatments among mineral fertilizers mainly contributed to amino acids residues in soil. The PLFA profiling exhibited that increased amino acids under OM and HOM correlated significantly (p <= 0.05) and positively with an increase of Gram-positive (G+ve) bacteria and fungi, negatively with actinomycetes, and non-significantly with Gram-negative (G-ve) bacteria. These results suggest that accrual of organic and microbial residues (G+ve bacterial and fungal) enhance the N stabilization in surface soil, which ultimately could increase the plant growth and yield of crops.