Nitrogen recovery from fertilizers and contribution of biological nitrogen fixation as a function of inoculation with plant growth-promoting bacteria associated with 15N-urea rates in maize crop

Abstract

Nitrogen (N) fertilization is one of the highest costs in the production process of non-leguminous crops such as maize. Developing management practices which minimize the reliance on chemical N inputs are critical for global food security and environmental sustainability. Recent research have demonstrated the potential of using plant growth-promoting bacteria (PGPBs) with a bias to increase the use efficiency (NUE), recovery of N applied via fertilizers, in addition to a small contribution to biological N fixation (BNF) on cereal crops, reducing N losses in agricultural systems. More detailed studies using refined techniques such as the isotopic technique (15N) are needed to provide relevant information about the potential of BPCPs such as Azospirillum brasilense and Bacillus subtilis associated with N rates to increase the recovery and accumulation of N-fertilizer application, and N contribution from atmosphere by BNF, benefiting the development and growth agricultural interest crops. This study aims to evaluate, in a greenhouse condition, the N accumulation in plant and N-recovery from fertilizers as a function of inoculation with A. brasilense and B. subtilis applied individually, or in co-inoculation, associated with 15N-urea rates. The N accumulations in shoots and roots (total N, N-NO3- and N-NH4+), the percentage and total amount of N from the labeled fertilizer and other sources (such as atmosphere - contribution by BNF), soil, organic matter, among others will be determined) and N-recovery from applied fertilizers. In addition, shoot and root dry mass will be determined, as well as the contents of chlorophyll, flavonols and the N balance index in the leaves. The hypothesis of the study is that A. brasilense and B. subtilis associated with N rates would increase the N use efficiency in plants due to the enhanced use and accumulation of N-fertilizer applied, with a contribution of N input from BNF, providing greater growth and biomass production in maize plants. (AU)