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

Start Date: 2017
Principal Investigator: Dan Kaiser
Organization: University of Minnesota, Department of Soil, Water, and Climate
Status: Completed

Background Info

An increased emphasis for reducing nitrate loss to surface and ground water has increased the number of tools available to farmers to help reduce the potential of nitrate loss through fine-tuning of nitrogen rates in-season. Currently, split-application of N is suggested in south-central and south-eastern Minnesota where climates are more prone to leaching. With more farmers interested in variable rate N some of the new tools available need to be researched better to determine if they can provide a better estimation of optimal N rates compared to the current practices suggested with the MRTN approach.

Objectives

Compare the effectiveness of models of adjusting corn N rates in-season for corn

Determine if late season rescue N can increase corn grain yield

Key Findings

This research has brought up two questions about using models. The Climate Pro model only gives a predicted surplus or deficit and did not provide any guidance on application rate so determining the actual need for N is difficult. In addition, if the data clearly shows that the amount of N required is more important than when it is applied, there should not be impact of timing on the surplus or shortfall of N unless the measured values are at shallower soil depths. However, if roots are taking up nitrogen at deeper then the amount of N remaining at shallower depths may not be overly critical. While on-farm data does how the models can be used to achieve maximum yield, the cost benefit needs to be accounted for as well as the accuracy across many field locations.

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