Residue effects, how to figure value

By Delta George

K-State Research

and Extension Agent

_

There are many ways to put a value on crop residue. To determine a value, producers could calculate: the amount of nutrients in the residue; the amount of organic carbon in the residue, then estimate how much the residue might increase organic matter levels in the soil; the tons of soil saved through reduced water and wind erosion; or the increase in soil moisture levels, and the potential effect on yield. Producers could also take the direct approach and find out how much someone is willing to pay for it.

However the value is calculated, it is obvious that crop residue is not a waste product, though some people still consider it as such. Residue will actually improve profits in several ways. Most would say that the greatest benefits of residue would be its effect on erosion control and stored soil moisture -- and ultimately crop yields.

Using crop residues to protect the soil surface is the single most effective way to control erosion. The effect of residue on water erosion begins with the initial impact of raindrops. When water drops hit crop residue, the water loses its energy and gently seeps into the soil, as opposed to splashing and loosening the soil particles. Bare soils can lose up to 30 tons per acre topsoil annually. In no-till where residue is left or on land in permanent cover such as CRP, annual soil losses are often less than 1 ton per acre.

Wind erosion can have a similar effect on bare soil. Wind lifts soil particles from the surface and drops them back to the ground. Standing crop residue raises the wind profile off the soil surface, providing lateral wind protection for 10 times the height of the residue.

Crop residues also increase soil moisture levels, by improving water infiltration and reducing evaporation losses. Having at least 2,000 pounds of residue on the soil during periods when no crop is actively growing typically adds about one inch or more of available stored water to the soil profile.

Residue improves water infiltration by providing physical barriers to water runoff, protecting the pore space in the soil, and preventing crust formation on the soil surface.

Evaporation rates can decline dramatically when the soil is protected with residue. Residue blocks solar radiation from the sun and keeps the soil surface cooler.

In general, more moisture will be stored in the soil when the residue remains standing upright for as long as possible; primarily because the standing residue raises the wind profile higher off the ground from the soil surface -- the site of the evaporation process. Also, residue standing during winter months provides more opportunity for capturing snow and keeping it in the field than residue that is lying flat.

The bottom line is that crop residue provides considerable value to the producer even if it is left on the soil surface rather than sold as a source of biomass. The exact monetary value can be calculated in several ways, but perhaps the greatest value is the protection of the soil resource, the additional soil moisture stored during non-crop periods, and the more efficient crop use of the water supply during the growing season. Every extra inch of conserved water can add several bushels of production to the land, depending on the crop and whether the minimum threshold has been reached. This can easily add up to $50 per acre or more at today's crop prices.

To maximize the use of residue, producers should:

* Maintain as much residue for as long as possible, especially during the erosion critical period in the cropping system,

* Harvest the crop at the tallest height practicable,

* Spread residue evenly at harvest, and

* Maintain stubble in a standing position.

For further discussion and information on the value of crop residue, see publication MF-2604, "Value of Crop Residue," HYPERLINK "http://www.oznet.ksu.edu/library/crpsl2/mf2604.pdf" http://www.oznet.ksu.edu/library/crpsl2/mf2604.pdf.

Editor's Note: This article was adapted from the K-State Research and Extension E-updates, March 2008. Delta George is a K-State Research and Extension agriculture and 4-H extension agent assigned to Bourbon County. She may be reached at (620) 223-3720.