Does N fertilizer rate affect microbial benefits to early maize growth? An evaluation of Iowa-isolated microbial communities.

Abstract

Chemical nitrogen fertilizer is commonly used in maize production and is a necessary part of achieving maize yields seen in Iowa today. Despite nitrogen fertilizer’s usefulness, its manufacture and use at current rates are significant sources of air and water pollution. Nitrogen fertilizer use has increased in Iowa while crop diversity has dramatically decreased since 1950, changing soil microbial communities’ makeup in crop fields. Use of synthetic microbial communities based on microbes isolated from maize roots in diversified cropping systems, using low amounts of chemical nitrogen fertilizer inputs may provide another sustainable method to help supply nitrogen to maize plants. This experiment explores the effects of various synthetic microbial communities on nitrogen-associated plant growth metrics in early-season maize. Plant metrics examined included development stage, plant height, chlorophyll content and dry root and shoot weight in both reduced and grower-typical nitrogen environments. Interesting trends were seen in plant height, with the Rhizobiales synthetic community showing the largest numerical values in reduced nitrogen soil for most measurement times. Plants treated with the MARSc community (SynCom) produced significantly larger root weights compared to other treatments in reduced nitrogen soil and produced the largest root weight of the synthetic communities in grower-typical nitrogen soil, although not significantly. Overall, synthetic community performance was encouraging, especially in reduced nitrogen. Research should continue into synthetic communities to determine their ability to repeat the results produced in this study, as well as to refine the makeup of synthetic communities to make them more beneficial to maize.