Effect of Nitrogen Rate and Residue Management on Soil Water Status and Yield.

Water and nitrogen are critically important for corn production. Too much or too little of either can have devastating effects on grain yield. The objective of this field research was to evaluate the interaction between carbon and nitrogen and its impact on soil water status and plant water use by manipulating carbon (residue removed or retained and incorporation) and nitrogen (N) rate (0 and 224 kg N ha^-1) in a continuous corn rotation replicated four times. The experiment was conducted on a Canisteo soil (Fine-loamy, mixed, superactive, calcareous, mesic typic endoaquolls) in southwest Minnesota, USA. Volumetric soil water content (VWC) was continuously monitored for two replications of two N treatments during the growing season in 2014 and 2015. Volumetric soil water content was measured at 0.1 and 0.2 m depths below the soil surface. Preliminary results showed that frequency and intensity of precipitation events impacted whole season soil profile daily water content for both years. In 2014, during the critical growth period between V18 and R3, the soil profile where full residue was returned (FRR) contained more water for the 224 kg N ha^-1 treatment than the 0 kg N ha^-1 treatment. Where low residue was returned (LRR) there was virtually no difference in the amount of water. In 2015, during the same time period the data showed generally more water under FRR compared to LRR regardless of N treatment. Additional results for grain yield, evapotranspiration (ET) and water use efficiency (WUE) will be presented. Midwestern cropping systems of the future will need to be sustainably intensified in order to be high yielding while simultaneously conserving water and nutrients.