PS 33-150 - CANCELLED - Managing the maize microbiome for sustainable nutrient retention in Illinois agricultural soils

Background/Question/Methods

Illinois corn producers have taken a greater interest in improving the efficiency of nitrogen (N) use due to high fertilizer costs and concerns about water quality issues. The hypoxic zone in the Gulf of Mexico attained its highest recorded area in 2017, and this has brought even greater attention to issues of N loss from conventional agricultural systems. Understanding the ecological drivers that govern microbial transformations, such as N fixation and nitrification, can lead to the management of soil microbial processes to improve the residence time of soil N. Our objectives for this project are to focus on plant-microbe interactions that affect plant nutrition and soil N retention. Here we are investigating how new microbial-focused agronomic approaches alter soil N holding capacity. Specifically, we examine how microbial-associated phenotypes (MAP) of biological nitrification inhibition (BNI) and a N-fixing inoculant (Klebsiella variicola) interact synergistically to shape N fertilizer use in maize production. We tested these technologies in the field under three N rates (0, 30, and 60 lbs N/acre), with/without an N-fixing inoculant, and with/without a BNI trait in a corn inbred (B73).

Results/Conclusions

We found throughout the growing season, that the presence of the BNI trait tended to reduce nitrification rates when compared to B73. From the N-fixation assays, we did not find a significant effect of N-fixing inoculant but, did observe higher levels of ammonium in inoculated plots indicating that these N-fixing inoculants are fixing atmospheric N into the plant-available form of ammonium in soils. When N was less limiting (60 lbs N/acre), applications of the N-fixing bacteria tended to increase plant N accumulation and these improvements in N uptake were most apparent when the BNI trait was present. We also observed some benefits from both the BNI trait and the N-fixing inoculant on grain protein concentrations, indicating improved N partitioning into grain tissues. Overall, these results suggest that combining MAPs and N-fixing inoculants could be a way to improve plant nutrition and maintain N in the agroecosystem.