Submitted to: Precision Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/31/2003
Publication Date: 6/20/2004
Citation: Harmel, R.D., Kenimer, A.L., Searcy, S.W., Torbert, H.A. 2004. Runoff water quality impact of variable rate sidedress nitrogen application. Precision Agriculture. 5(3):247-261. Interpretive Summary: As agricultural producers are faced with increasing pressures to decrease costs, increase yields, and protect the environmental, new techniques are needed to achieve these goals. One recently-developed farming practice is precision farming. Precision farming techniques consider how soil and crop conditions change over the field and allow different fertilizer or pesticide application rates at different locations within the field where they are most beneficial to crop production. This prevents over application in areas where application is not needed or would not provide crop production benefits. The objectives of this study were to evaluate the water quality and crop yield impacts of precision application of nitrogen (N) fertilizer. This study was conducted in Bell County, Texas, on two adjacent fields. Fertilizer was applied uniformly to the conventional field at about 135 kg/ha and to the precision field at a range of 100 to 160 kg/ha. In this study in the Texas Blackland Prairie, precision N application did not result in drastic water quality differences compared to convention uniform rate N application. Also, precision application resulted in similar corn yields for both fields even though less N was applied to the precision field.
Technical Abstract: Precision agriculture, also referred to as site specific management and variable rate technology, can be simply defined as input application across a field based on variable requirements for that input. In recent years, precision agriculture has received attention from producers, agribusiness, and governmental agencies in an effort to increase profitability and protect the environment. The objectives of this study were to evaluate the water quality and crop yield impacts of precision application of nitrogen (N) fertilizer, which was based on corn yield monitoring. This study was conducted in Bell County, Texas, on two adjacent fields. Two years of corn yield data from the precision application field were collected under conventional uniform N application prior to precision application. Then for two more years, one field was fertilized using uniform N application, and the other was divided into management units designated as poor, moderate, and high based on measured yield potential. Fertilizer was applied to the precision field at an approximate range of 100 to 160 kg/ha. To monitor surface runoff, H-flumes equipped with automatic samplers were installed in each field. The liquid and solid fractions of collected samples were analyzed for N and phosphorus (P) constituents. In this study, precision N application did not result in drastic water quality differences compared to convention uniform rate N application with nitrate concentrations for both treatments averaging between three and five mg/l. Also, precision application resulted in similar corn yields for both fields even though less N was applied to the precision field.