Evaluation and Calibration of In-Season Tools for Detecting Nitrogen Stress in Corn

Summary

• Cordova: Modeled data suggested a reduction of 12 or 18 lbs of N for the North and South field block, respectively, versus 70 lbs of N applied pre-plant and 70 lbs of N applied side-dress. Corn grain yield did not differ whether among the fixed-pre plant or the two side-dress treatments indicating that 140 lbs of N applied pre-plant would be sufficient for this location. The reduction in the amount of N based on the variable rate treatment did not cover the additional cost for using the crop model plus additional application costs.
• Clarks Grove: Side-dress N application resulted in an increase in yield of 5 bu/ac compared to 140 lbs N applied all before planting. Modeled data suggested a reduction of 13 lbs of N versus 70 lbs of N applied pre-plant and 70 lbs of N applied side-dress. There was no yield difference on average between the variable rate and fixed side-dress N application treatments. Similar to Cordova, the cost reduction in N for the model and variable rate technology did not cover their cost and a planned flat rate split application would have been sufficient at this location.
• The models all predicted a lower N requirement than the flat rate treatment. Any benefit to the model would thus be associated with cost savings on N as it would not be expected to get a yield increase when less N is applied. Application rates based on the models were consistent with current MRTN suggested rates for corn production in Minnesota.
• Waseca: The data collected at Waseca found no evidence that side-dress application of N would result in a lower N requirement for corn. The total amount of N required for the pre-plant was the same as the combination of pre-plant plus N side-dressed at V5 or V10. Model output tended to under predict N requirement at the small plot location. Sensor technology also was used to assess N requirement but did not perform better than models (data not included).