On Hood's Perthsire Farms, he tested models for cotton and soybeans for ARS plant physiologist Vangimalla R. Reddy, who is with the agency's Alternate Crops and Systems Laboratory in Beltsville, Md. Hood is also pioneering the effort to link the models to a precision farming operation.

He uses computers on-board harvesters for on-the-go yield monitoring. He also hires pilots to fly over his fields and take infrared photographs that show crop vigor.

Crop growth models predict all aspects of farming through harvest, including water, fertilizer and chemical needs.

Gossym, the ARS cotton model, even tells Hood about the threat posed by boll weevils and other insects. Comparing that information to aerial photographs and yield data enables Hood to judge whether predicted losses make spraying cost-effective.

Gossym has served as the template for all subsequent ARS crop growth models, which now cover a total of seven crops.

Reddy works with farmers throughout the country to develop the models. He continues to fine-tune the cotton and soybean models and is developing similar models for corn, wheat, rice and potatoes.

His colleague, Jeff Baker, developed a melon model that is also in use. The cotton, melon, potato and soybean models are all available on the Internet or on CD. The Cotton Production Model, Gossym's successor, was released this year for more research and development.

ARS has signed a cooperative agreement with Florida A&M University in Tallahassee to field-test the crop growth models on small farms owned by minority farmers.

The crop growth models can also be used for scientific applications such as studying the effects of global warming on crop yields or lowering nitrogen levels in bodies of water like the Chesapeake Bay.

ARS is the U.S. Department of Agriculture's chief scientific research

agency.