By Rebekah Ray

MISSISSIPPI STATE -- Two Mississippi State University researchers showed that combining remote sensing and variable rates of fertilizer application helps cotton production on different types of soils.

Using a test plot located in the North Delta, Dr. Jac Varco and MSU research assistant John Thompson studied cotton's performance under different conditions.

"To the human eye, soil may appear uniform in texture and characteristics, but different soils with different chemical compositions may exist within a field, and that can affect crop production," Varco said.

Until recently, Mississippi Delta cotton farmers did have not have the tools to vary application rates of nitrogen within fields. Nitrogen is essential for plant growth. Soil microorganisms release the chemical as they feed on organic matter and plant residues. Nitrogen fertilization increases photosynthetic activity and plant growth, and produces healthy looking plants with a dark green color.

"Remote sensing can help distinguish different soil textures, elevation and drainage patterns in a field so that nitrogen fertilizer can be applied more appropriately," Varco said.

Over-application of the nutrient can delay crop maturity by causing excessive growth and increasing insect infestation and boll rot. Controlling plant height in cotton is critical for effective use of insecticides and mechanical harvesting.

Researchers from the Institute for Technology Development located at the Stennis Space Center in Picayune used Lidar, or laser radar, to determine soil elevations on the Delta test plot. They also used multispectral imaging to distinguish soil moisture patterns. By coupling this information with soil elevation measurements, they could predict drainage.

Cotton was planted and nitrogen applied to the field uniformly. The researchers mapped 72 acres of the site on a 1-acre grid using a global positioning system to show soil characteristics.

The researchers established a control section and two test sections that were treated with variable rates of nitrogen. One test section was fertilized according to soil test results, and the other used that same information and included elevation, soil moisture and clay percentages. The control plot received 40 pounds of nitrogen per acre.

Over the growing season, researchers measured plant heights and leaf nitrogen status, and used remote sensing to determine how variable rate fertilizer nitrogen applications affected cotton growth.

This research was done in conjunction with NASA's Commercial Remote Sensing Program and ITD/SSC.