GPS Helps Put Manure Where It Counts

Farmers need greater accuracy when applying livestock waste to their fields, to maximize crop yields. Agricultural Research Service scientists at the Soil and Water Conservation Research Laboratory in Lincoln, Nebraska, are working on ways to hit the target and protect groundwater.

Soil scientist James S. Schepers has been studying how to increase the odds of hitting the target with site-specific applications. His overall goal is to improve groundwater quality and prevent leaching of specific chemicals, such as nitrates, into groundwater.

Valuable nutrients found in livestock wastenitrogen, phosphorus, and potassium--can be lost if not applied where crops can use them. Schepers uses GPS (global positioning system) satellite technology to help farmers identify low-yielding areas in fields and to put nutrients where they are most needed. The wide difference in nutrient availability that can occur in soil within the relatively small space of a single field is referred to as spatial variability.

Most livestock manure is broadcast and is not applied uniformly or to a specific site. Farmers fertilize an entire field and, after adding manure, may eventually double or triple the required nutrient level in some parts of the field while neglecting others, says Schepers.

ARS research uses GPS--a combination of satellite technology and computer programs--to draw a map of a specific crop field that includes such information as per-acre yield data collected during harvest. Such data can be used to determine where manure application might be appropriate.

GPS helps farmers be more cost efficient and environmentally sensitive than traditional broadcast methods of commercial fertilizer or manure application allow.

"This approach is one aspect of precision farming," Schepers says. "But convincing producers to apply the manure on a site-specific basis will require them to recognize spatial variability in crop growth and yields. GPS technologies make it possible to easily locate these variable areas." 

Good old-fashioned followup is also required. Farmers will still have to scout their fields on foot to determine the causes of nutrient deficiencies. 

"There is no substitute for getting down and looking at the crops," says Schepers, "but GPS can help farmers do a better job of addressing problems."--By Dawn Lyons-Johnson, Agricultural Research Service Information Staff.

James S. Schepers is in the USDA-ARS Soil and Water Conservation Research Unit, University of Nebraska, 119 Keim Hall, P.O. Box 83934, Lincoln, NE 68583; phone (402) 472-1513, fax (402) 472-0516.

"GPS Helps Put Manure Where It Counts" was published in the June 1998 issue of Agricultural Research magazine. Click here to see this issue's table of contents.