Rees: Yield & Soil Impacts from Grazing Corn Residue

With pastures short on grass due to drought, it's a blessing for producers to get cattle out on cornstalks. Sharing an update on long-term research showing no negative impacts to the subsequent yield or soil from cattle grazing corn residue.

Mary Drewnoski, et. al share on yield impacts, "Two studies were conducted to evaluate the effects of corn residue harvest on subsequent crop yields. In a long-term study (16 years), cattle grazing corn residue in the spring (February to the middle of April) or the fall (November through January) slightly improved subsequent soybean yields and had no effect on corn yields in an irrigated field maintained in an annual corn-soybean rotation at Mead, Neb. In a five-year study, fall grazing (December through January) or baling of corn residue had no effect on subsequent corn grain yields in a field maintained in continuous corn production at Brule, Neb. These data suggest that the grazing of corn residue in the fall or spring at or below UNL recommended stocking rates will have slightly positive or no impacts on subsequent soybean or corn yields.

The stocking rates utilized were consistent with UNL grazing recommendations, which result in removal of half the husks and leaves produced (8 lb of leaf and husk per bushel of corn grain produced). The corn yields ranged from a low of 186 bu/ac in 2004 to a high of 253 bu/ac in 2009, with a median over the 16 years of 203 bu/ac. Recommended stocking rates would have ranged from 2.1 to 2.9 AUM/ac with a median of 2.3 AUM/ ac."

Dr. Mary Drewnoski wrote an updated Beefwatch about soil compaction and grazing. "One of the most common concerns about grazing corn residue is that cattle will cause soil compaction. A long term grazing data (16 years) conducted at the UNL has shown no compaction when grazing in the fall or the early spring. In this long-term study, grazing did not impact soil nutrient content. This fits well with expected impacts given that cows in mid-pregnancy retain very little nitrogen, phosphorus or potassium. Thus, they excrete in manure and urine most of what they consume resulting in very little nutrients being removed from the land. With long term grazing there was an improvement in subsequent soybean and corn yields. This could have been due to the nutrient cycling being sped up as there is an increase in microbial biomass in the soil in the grazed areas.

More recently, a study was designed to test an extreme scenario for spring grazing. The thought was that if grazing was to cause compaction, it was most likely to happen when the soil is wet and thawed and when a high stocking density was used. The field was grazed at the recommended rate by starting in mid-February with 3 hd/ac for 45 days (normal stocking) or starting in early March with 9 hd/ac for 15 days (high stocking). Turn out of the higher stocking density groups was delayed until it rained to have the worst-case scenario. All groups were removed mid-March. There were some minor increases in bulk density (measure of compaction). The penetration resistance was also higher, and thus more down pressure had to be applied to get the soybeans planted. Down pressure applied at planting was 265 lbs in the non-grazed and 290 lbs in the grazed treatments. Much of the increase in penetration resistance is due to the soil having less cover and thus less surface soil moisture. The planting speed was also reduced due to the surface roughness. However, the subsequent soybean yields were still improved by grazing. While it is not recommended to graze late into the spring as this does have some downsides when it comes to planting, if cattle happen to be left out when a warm-wet spell occurs, there is no long-term damage to the land.

Overall, when managed correctly, grazing corn residue can be a win-win for both the crop and cattle producer. Want to see the data for yourself? Check out these Nebraska Beef Reports:"

Effect of Corn Residue Removal on Subsequent Crop Yields

Effect of long-Term Corn Residue Grazing on Soil Properties

Effect of Corn residue grazing or Baling on Subsequent Crop Yield and Nutrient Removal

Impact of Spring Corn Residue Grazing on Soil Physical Properties and Crop Yield

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