Corn residue is a valuable resource for cattle grazing

According to a new study from the American Society of Agronomy, harvested fields that are covered with corn residue in the late fall may seem useless, but these husks, kernels, and cobs are actually a valuable resource for cattle grazing. The researchers identified a positive association between cattle grazing corn litter and soybean yields.

The research shows that corn residue can increase farm income and provide affordable cattle feed. Lead author Morgan Grabau studies the interactions between cattle grazing and crop productivity. 

“Corn residue is an under-used resource. Only 15% of the corn residue acres in the central U.S. are grazed,” said Grabau.

When it comes to cattle grazing corn residue, many farmers are concerned about soil compaction. If the soil is compacted too much by cattle, future crops may not be able to grow well. 

In the past, Grabau’s team has shown that compaction is not too bad during fall and winter grazing. This is because when the soil is dry and frozen, it resists stamping cattle hooves. “My research was focused on the effect of grazing in the spring when the soil is thawed and wet,” explained Grabau.

The team investigated two different types of grazing systems. In one system, the researchers let a small number of cattle graze corn fields for 45 days beginning in mid-February. The second system tripled the number of cattle, yet cut grazing time to just 15 days in March. In other words, the total amount of grazing was equal while the time spent on wet fields varied, which could affect how the soil responds to being trampled.

The analysis was based on farmland in Nebraska, where around half of the corn fields are grazed after harvest. The researchers measured various factors that contribute to soil compaction, and also measured soybean yields during the season after cattle grazing. This experiment was repeated over two years.

“Much like previous fall grazing studies, minimal effects were seen on soil properties and yield due to spring grazing, regardless of the number of cattle and area grazed,” said Grabau. 

In addition, highly concentrated grazing for just 15 days was found to increase soybean productivity. “This yield increase could be due to more residue removed, causing warmer soil temperatures for plants to grow.”

The cattle did cause some soil compaction, but the effects were limited to the surface level of fields. “Compaction isn’t permanent,” said Grabau. “Soil can loosen up again as it dries and saturates over and over, and microbial activity in the soil also reduces compaction.”

The experts found that soybean seedlings were able to establish themselves in the soil after cattle grazing even with some surface compaction present.

“Even when we created a worst-case scenario, grazing in the spring when the ground was wet, compaction was minimal and subsequent soybean yields were not negatively affected,” said Grabau. She noted that fall and winter grazing is probably the best solution, but farmers should not be afraid of grazing cattle in the spring.

“The integration of crops and livestock is a beneficial production system. Grazing cattle on corn residue can be a great way to make even more food for human consumption from corn fields, as both the corn grain and plant residue can be used as feed for livestock.”

The research was presented at the 2020 ASA-CSSA-SSSA Annual Meeting.

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By Chrissy Sexton, Earth.com Staff Writer