Effect of Proximus® on Soil Nitrate Concentrations, Plant Dry Matter, and Yields.

Our goal was to determine the effect of Proximus® on soil nitrate concentrations (NO₃^-), plant growth, and crop yields under commercial field conditions. Eight locations across the Corn Belt were selected. All growers utilized urea ammonium nitrate (UAN) as the source of N. Each location was subject to the individual growers’ practice except a portion of the field had Proximus® co-applied with UAN at a rate of 9.5 L Proximus™ 45 kg-N^-1. Soil samples were collected to a depth of 15 cm approximately every 14 to 21 days. Samples consisting of 10 maize plants were collected at R1 to assess dry matter accumulation and N content. At harvest a hand sample of 15 ears was collect to assess both the kernels per ear and kernel weight. Soil results indicated a 22.7 % reduction of NO₃^- at peak nitrates after N application with a season average reduction of 15.6 % NO₃^- for the Proximus™ applied treatment compared to the UAN control. Plant DM at R1 for the UAN control averaged 134.1 g DM plant^-1 across all locations while the Proximus® treated plots averaged 163.4 g DM plant^-1, respectively. This DM increase directly resulted in greater N content of 0.5 g N plant^-1 in Proximus® treated areas. Lastly, plants that received Proximus™ produced ears that contained on average an additional 61 kernels ear^-1; which translates to approximately 1300 kg ha^-1. These data support the hypothesis that Proximus® is effective at reducing soil NO₃^- in the sampling zone while enhancing plant DM and yield.