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ARS Home » Plains Area » Lincoln, Nebraska » Agroecosystem Management Research » Research » Publications at this Location » Publication #254661
Title: Derivation of a Variable Rate Nitrogen Application Model for In-Season Fertilization of Corn

Author
item HOLLAND, KYLE - Holland Scientific
item SCHEPERS, JAMES - Retired ARS Employee

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2010
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fertilizer used in corn and wheat production can potentially pollute surface and ground water if excessive amounts are applied. In addition to the environmental damage the lost fertilizer represents a financial loss for the farmer. Sensors have been developed that can detect when corn and wheat are nitrogen deficient. This study developed a model that uses sensor data to determine the amount of nitrogen fertilizer needed to optimize grain production. This model has the potential to be used with crop sensors so that nitrogen fertilizer is applied at the proper rate to areas of the field where the crop is nitrogen deficient.

Technical Abstract: Nitrogen fertilizers used in crop production contribute to pollution of groundwater by nitrate and occurrence of hypoxia in the Gulf of Mexico. Economic and environmental pressures are forcing producers to improve nitrogen use efficiency. The objective of this study was to develop a production-based in-season nitrogen (N) recommendation model for use with crop canopy sensors and remote sensing data. The approach is based on the general shape of an N fertilizer response function (sensor index versus N rate) and the relationship between N rate and in-season crop vegetation index data. Transformation and substitution techniques were used to generate a simple function that offers an N fertilizer recommendation based on spatially variable in-season remote sensing data and established local crop production information such as the economic optimum N rate or producer defined optimum N rate. The model accommodates management zones, preplant N applications, manure mineralization, legume credits, nitrate in irrigation water, and crop growth stage. Estimates of potential yield are not needed. Instead the method relies upon production information provided by the user and the generalized shape of the fertilizer N response function. Testing the model with SPAD chlorophyll meter data from irrigated corn showed that the recommended fertilizer N rate plus preplant N rate totaled 184, 164, 186, 188, and 200 kg ha-1 for preplant N rates of 0, 50,100, 150, and 200 kg N ha-1 when averaged across growth stages for three years.