Can crop residue be harvested sustainably in Michigan?

Livestock feed and bioenergy are creating new markets for crop residue such as corn stover. Careful attention to removal rates can help maintain soil productivity.

As farmers are asked about their interest in supplying the growing demand for crop residue, most often corn stover, they quickly bring up the issue of maintaining soil productivity. Many farmers value the content of soil organic matter and see it as a measure of the soil to produce a high yielding crop.

Markets for crop residue such as biomass pellets for combustion or feedstocks for cellulosic ethanol production are not well established in Michigan. At the same time, the loss of hay acres and short 2012 crop in many areas has caused an increase in livestock feed prices throughout the state which has beef and dairy producers evaluating alternative feedstocks, especially corn stover.

For some farms, soil productivity is not at optimum levels and therefore these farms may not be good candidates for crop residue removal while others may benefit from reducing residue to draw-down very high nutrient levels and allow future manure applications. A few calculations can help you to evaluate if and how much corn stover may be sustainably removed on your farm.

First, it is important to know that only about 20 percent of crop residue winds up in the soil organic matter pool. The other 80 percent is respired by soil microorganisms as they convert the residue into more stable soil carbon. Additionally, about 2 percent of existing soil organic matter is decomposed annually. On a typical Michigan soil, about 6,250 pounds of crop residue are needed each year to replace these losses. On the soil organic matter input side, the average production of crop residue from a corn-soybean rotation is 7,865 pounds per year (corn 11,281 pounds and soybeans 4,450 pounds). This allows the removal of 1,615 pounds (7,865 pounds to 6,250 pounds) of crop residue annually while maintaining soil organic matter levels at about 2.5 percent. Since it is likely that soybean residue will not be removed, 3,230 lb (1,615 annually x two years) of corn stover per acre could theoretically be removed every two years.

Crop residue production per year

Corn

11,281 lbs.

Soybeans

 4,450 lbs.

average

7,865 lbs.

Soil organic matter loss

Loss from respiration 2% per year

 

Crop residue equivalent 1,250 lb./0.2

6,250 lbs.

Sustainably available for harvest

1,650 lbs.

Michigan State University Extension continues to conduct applied research and educational programs to help producers make informed decisions of harvesting crop residue. This work includes harvest methods like chopping, windrowing and bale type like large square or large round.

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