Soil inoculation with nitrogen‐fixing bacteria to supplement maize fertilizer need
Logan P. Woodward, Connor N. Sible, Juliann R. Seebauer, Frederick E. Below
Abstract
Abstract Nitrogen (N) is an essential plant nutrient, but low and variable plant‐available N levels in agricultural soils often limit maximum grain production. The objective of this study was to determine if a free‐living nitrogen‐fixing bacterial inoculant (NFI) could supply biologically‐fixed N as an additional N source and if this enhances maize ( Zea mays L.) N uptake and grain yield. Maize was grown at four site‐years in Illinois during 2019–2021. The NFI, a mixture of edited Klebsiella variicola and Kosakonia sacchari , was applied in furrow at planting with urea‐N rates from 0 to 225 kg N ha −1 . Using quadratic regression models, across N rates, the NFI supplemented the fertilizer‐N equivalent of 38.5 or 12.1 kg N ha −1 at V8 or R1, respectively. Increases in N accumulation were observed in all plant fractions, and δ 15 N abundance measurements confirmed that some of this additional N was derived from biological N fixation. The NFI treatment increased N accumulation by an average of 4.8% and 3.7% at V8 and R1, respectively, which was the result of greater biomass, with no effect on plant N concentration. Application of NFI resulted in an average of 1.5% more kernels m −2 and 0.11 Mg ha −1 more grain yield. This work reveals that NFI can provide an additional source of N for maize production but identifies that the season‐long benefit of fixed‐N from an NFI is yet to be fully optimized.