Managing Water and Nitrogen Using a Site-Specific Center Pivot

Innovative modifications that Agricultural Research Service scientists have made to a center-pivot irrigation system will allow farmers to apply varying amounts of water and chemicals simultaneously, depending on the site-specific needs of plants.

ARS scientists in Florence, SC, are fine-tuning the controls for the modified center pivot. It can independently water and treat nearly 700 areas within a 14-acre circle. Each area is about the size of a two-car garage.

The modified center pivot consists of thirteen 30-foot-long segments. Each has three sets of sprinklers, and each set can apply water at a different rate. Up to eight different water-application rates can be used for any given speed of the system. A computer controls the system, driven by specialized software and a database containing information about the soil, crops and farming practices.

The scientists say site-specific application of irrigation water and fertilizer can conserve water, reduce the chance of crop stress from drought or flooding, and reduce leaching of fertilizer or pesticides to groundwater.

Since 1995, the scientists have tested and improved the system by applying water to

selected regular-shaped corn and soybean plots and nitrogen to corn. In the future, they'll use it to manage variable-rate applications of water, nutrients and pesticides to highly variable areas with irregular-shaped boundaries.

This site-specific center pivot can be used to manage each area within the fields most efficiently and profitably to optimize crop yields while protecting the environment. The system does this by applying the proper amount of water or nutrients to each area according to its environmentally acceptable production capacity.

Scientific contact: Carl R. Camp, ARS Coastal Plains Soil, Water and Plant Research Center, Florence, S.C., phone (843) 669-5203, ext. 107, fax (843) 669-6970, camp@florence.ars.usda.gov.