Soils at Risk from Compaction When Spreading Manure

June 26, 2008

LONDON, Ohio -- Crop fields can be at risk from compaction when spreading manure just as much as when using any other farm equipment. Visitors to the Great Lakes Manure Handling Expo can learn how to minimize the impacts of manure-spreading equipment on soils.

Randall Reeder, an Ohio State University Extension agricultural engineer, will discuss compaction and manure handling equipment at the event, which will take place July 9 at the Molly Caren Agricultural Center in London, Ohio. The expo will run from 8:30 a.m. until 4 p.m.

"Farmers who spread manure know of the potential compaction damage to their soil. The good news, however, is that compared to large equipment on most grain farms, manure spreaders have less weight per axle," said Reeder, who also holds an appointment with the Ohio Agricultural Research and Development Center.

Unlike a 600-bushel grain cart, for example, which weighs about 20 tons on a single axle, most manure spreaders never go much above 12 tons on a single axle. As the size increases, the manufacturers add axles. The biggest ones have four axles, said Reeder.

"Compaction damage to soil is determined by a combination of axle weight, tire pressure and soil conditions. For most farms, a manure spreader will cause less compaction than a grain cart or combine, but more than a tractor," said Reeder. "For livestock operations the manure spreader may be the worst compacting vehicle, partly because it is often run on wetter soil."

Using a drag line system to pump liquid manure to the field is a good option for reducing compaction because only the tractor is run across the soil. Applying liquid manure through a pivot irrigation system during the growing season is even better, but is rarely used in Ohio.

Reeder offers the following tips to help minimize compaction when managing manure:

• Use bigger tires or rubber tracks to decrease the pressure on the soil. "Thirty pounds per square inch (psi) is a reasonable inflation pressure for the biggest manure spreaders although lower is always better," said Reeder. "Don't over-inflate the tires."

• Start with less than a full load of manure to minimize the impact of compaction. "Farmers are familiar with this practice when using grain carts on wet soil. They don't fill the grain cart to capacity when loading it in the field," said Reeder. "Of course the trade-off for spreading manure is that it takes more trips."

• Select fields based soil conditions. "Save the better drained fields for spreading when soil moisture tends to be high. Spread manure on poorly drained fields when it's dry," said Reeder.

• Plant cover crops. "Cover crops established after harvest of corn and soybeans provide more support for manure spreaders," said Reeder.

• Manage manure like any other fertilizer. "Apply manure only where you need it and where you'll get the most benefit," said Reeder.

• Where applicable, practice controlled traffic. "Under certain situations, it is possible for a manure spreader to be adjusted to match other equipment in a controlled traffic system," said Reeder. Controlled traffic is a method to manage soil compaction, whereby all farm equipment operates the same width and wheels are spaced the same so that traffic is confined to specific paths year after year, and the remainder of the soil is untouched.

Nearly two decades of Ohio State University research on Hoytville silty clay loam has shown that through compaction from a 20-ton per axle load, 10 percent of potential crop yield may be lost, reducing income by thousands of dollars for large operations.

The theme of the Great Lakes Manure Handling Expo is "The Economics of Recycling" and will include commercial field demonstrations, educational demonstrations, educational sessions, and commercial vendor displays.

The event is sponsored by Ohio State University Extension, the Ohio Agricultural Research and Development Center, Michigan State University, Purdue University, Penn State University and Cornell University. Additional sponsors include Ohio Composting and Manure Management and the Midwest Professional Nutrient Applicators Association.

To learn more, log on to http://ohio-environmental.org, http://oema.osu.edu, or contact Jon Rausch at (614) 292-4504 or rausch.7@osu.edu, or Mary Wicks at (330) 202-3533 or wicks.14@osu.edu.

Author(s): 
Candace Pollock
Source(s): 
Randall Reeder