Gage County
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Beatrice NE 68310
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News Column

Paul C Hay, Extension Educator

Fragile Crop Residue

Crop residue is important to crop producers because the natural carbon blanket reduces soil erosion, slowly increases organic matter levels, and improves soil structure and water infiltration rate. If crop producers can maintain 30 per cent crop residue cover after planting the 2005 crop they can reduce soil erosion levels in the field by 60 per cent. This is a very positive trade in particular because the carbon saved helps to improve soil organic matter levels being depleted by top soil erosion and the oxidation of tillage operations.

How do we get to 30 per cent cover after planting? It requires planning. Dryland corn and milo will have about 75-80 per cent residue cover after harvest. Irrigated grain crops will typically be about 90 per cent post harvest residue cover. Soybeans can vary widely from 30 per cent in a poor harvest year to 70 per cent after a good irrigated.

crop. So what's the problem! We have lots of residue material. Most farmers fighting the no-till trend will say this is plenty of residue to tie-up nutrients, keep the field wet, plug the planter, and still provide plenty of residue after a couple residue saving tillage passes.

Let's look at the facts.
Grazing stalks for 30 days, with a stocking rate of 1 cow per acre, will reduce residue cover by 50 percent. This is true even in soybeans where grazing activity is just bean hunting after the cow has filled up on corn stalks.
Weathering during the winter and spring will reduce cover by 10 to 30 per cent depending on rainfall and snow cover.
Anhydrous ammonia application with a slim line straight knife will reduce residue corn residue by 15 per cent and soybean residue by 25 per cent.
The planter or no-till drill also reduces residue by 10 per cent for the planter and 15 per cent for the drill.
Tandem disks will reduce surface residue cover by 50 - 60 per cent. Field cultivators are a bit less harsh and with wider sweeps (12 to 20 inches) will cover half the residue of a disk. Narrower sweeps (6-12 inches) will be closer a disk.
A skilled crop consultant can identify the crop rotation in a no-till field by examining the crop residue left from past years. These slowly decaying remnants of cob, stem joints, main stem pieces, etc add to the cover in the field. These are rare finds in tilled fields where soil organisms make quick work of anything coated in soil.

If you start adding up the losses, you might start saying even if I no-till I'm going to be short of the 30 per cent post planting target. Many long term no-tillers are using wheat on occasion and also using corn on corn in some years to increase crop residue cover on fragile soils. I think it is clear that any tillage operation at all is going to reduce soil residue cover in dryland fields below the target 30 per cent, and even in irrigated land tillage operations would have to be restricted to corn stalks.

View other Gage County News Columns & News Letters: http://gage.unl.edu/news/news.htm

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Extension is a Division of the Institute of Agriculture and Natural Resources at the University of Nebraska-Lincoln cooperating with the Counties and the United States Department of Agriculture.
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