Findings from research done by the Arkansas Agricultural Experiment Station have shown that the proper use of cover crops can produce several benefits for production systems in Arkansas including improved soil health, increased nitrogen, and additional weed control options.

A cover crop is a not-for-cash crop that is planted on a field off-season. The “cover crop” stops soil erosion and keeps and replenishes nutrients in the soil. Cover crops allow for much less tillage of the soil, which saves on fuel costs and reduces carbon emissions. It improves insect and weed control in fields as well as soil biodiversity and water collections.

Trent Roberts, associate professor of soil fertility and soil testing for the experiment station, the research arm of the University of Arkansas System Division of Agriculture said cover crops can also provide biomass to increase soil coverage and soil organic matter as well as aid in nutrient redistribution for the next cash crop.

While noting that some cover crops go better with certain cash crops, Roberts said having a plan for the next cash crop and goals of the cover crop are important.

A new episode of the Arkansas Row Crops Radio podcast provides more detail for those who have thought about trying cover crops. The episode see collaboration between Roberts along with cooperative extension service assistant professor and weed scientist Tommy Butts and soil health instructor Matt Fryer.

Mid-October is the latest recommended time to plant a fall cover crop like mustards or brassicas since they will typically “winter kill” and generate most of their above-ground biomass in the fall, Roberts said. But other cover crops like cereals and legumes will develop most of their biomass when they break dormancy in the spring.

Developing biomass is key to improving soil health, Roberts said.

Fryer also said in irrigated fields, a cover crop can improve plant growth by opening the soil profile to let water seep in deeper so the roots can pull water and nutrients farther down in the soil than the first six inches.

“Even small organic matter increases can give us pretty big benefits as far as moisture retention and water infiltration. So small increases don’t necessarily mean small benefits.”

While noting that some cover crops can be detrimental to certain cash crops, Fryer said winter pea, for example, has been shown to harm cottonseed germination and growth if the cotton is planted right after the cover crop’s termination. Cereal rye as a cover crop before corn is also not recommended.

“I always advise folks and caution people to not plant cereal rye ahead of corn,” Fryer said. “You’re likely to see a yield drag in corn even if you terminate early.”

He noted that cereal helps suppress small-seeded weeds like pigweed and crabgrass but does not suppress other large-seeded weeds. He added that Sorghum Sudangrass, on the other hand, is more beneficial in suppressing larger-seeded weeds like yellow nutsedge, which is an increasingly problematic weed in Arkansas.

“Whichever cash crop is planned, don’t plant annual ryegrass,”Fryer said.

Annual ryegrass is very resistant to herbicides and may end up being much more of a problem than a benefit, he said.

Fryer gave two rules of thumb on cover crops:

Fryer’s rule of thumb is 25% grass-based cover crop if followed by a grass cash crop like corn and rice, and 25% legume-based cover crop if followed by a legume cash crop like soybeans.

Roberts cautioned producers to always inoculate legume-based crops as many legume cover crops require a specific rhizobium that is not present in Arkansas soils.

For farmers who are thinking about cover crops, Roberts and Fryer encouraged just “dip a toe in the water” to start.

“Cover crops are going to help with weed control but they’re not a silver bullet,” Fryer said. “This is another tool in our arsenal against summer weeds.”

Likewise, Roberts noted that cover crops may replace some nutrients like fixed nitrogen, but they also require nutrients to grow. Some cover crops, he explained, are just better at “redistributing” nutrients.

“A lot of times what we’re doing is redistributing those nutrients within the soil profile,” Roberts said. “So, we’re potentially mining potash and phosphorus from lower soil depths and bringing them more up to the root zones of our cash crops.”

Roberts also said that it is a long-term commitment to rebuild soil through cover crops, but it is not the entire solution.

“Cover crops are not going to be the be-all,-end-all of solving fertility inputs or eliminating fertility inputs but they can help us take better advantage of the nutrients that we have in the profile,” Roberts said.

The U.S. Department of Agriculture’s Natural Resource Conservation Service has funding available to start a cover crop program, Roberts added. The funding, which helps pay for seed and termination costs, is limited to 350 acres and under.

Roberts said more people could be considering cover crops as the price of fertilizer continues to increase.

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