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ABSTRACT
A 5-year field study was conducted to improve nitrogen (N) and phosphorus (P) use efficiencies in wheat with the synergistic use of plant growth-promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi (AMF), and spectral properties for deriving need-based fertilizer N management decisions. Bio-fertilizer consortium inoculation on wheat seed improved rhizosphere mycorrhization, albeit native mycorrhiza also produced mycorrhiza colonization. Lower mycorrhiza colonization was observed in no-P and high P treatments at 30 and 60 days after sowing (DAS) when wheat seeds were not inoculated with bio-fertilizer. However, the mycorrhiza colonization was independent of the fertilizer P level at 60 DAS in the inoculated treatments. The integrated nutrient management with bio-fertilizer and need-based N use sustained highest grain yield with 16.7% and 25% less use of fertilizer N and P, respectively. The agronomic (AE) and recovery efficiencies (RE) of applied N and P were increased by 23.0% (AEN), 21.3% (REN), 40.2% (AEP) and 49.8% (REP), respectively. On-farm validation studies exhibited improvement in partial factor productivity of fertilizer P (PFPP) by 35.8% and fertilizer N (PFPN) by 22.5% in comparison with the soil test-based recommendation. The synergistic use of bio-fertilizer and need-based N management improved the PGPR population, dehydrogenase and alkaline phosphatase activities in soil. The improved soil microbiological properties attributed to better mycorrhization and microflora propagation in soil-facilitated nutrient assimilation and thus higher N and P use efficiencies in wheat.
Acknowledgments
The authors acknowledge the TERI (The Energy and Resources Institute), New Delhi, India, for providing different bio-fertilizer consortia to carry out this study.