Stine agronomists have been busy visiting with growers across the country about their planting plans for 2020. After a difficult year with preventive planting, flooding and other weather-related field issues, we’re hearing a lot of rumblings about cover crops. In this edition of Stine Weekly, we’ll look at cover crops, the benefits of using them and timing recommendations.
Types of Cover Crops
Cover crops are typically planted in the fall, either right before or right after a cash crop has been harvested. Their main purpose is environmental; they are not typically planted to sell, but rather for improving soil quality and controlling weed populations. A variety of cover crops are available: grasses, grains, legumes and brassicas.
Grasses are the most common cover crop as they are hardier and can overwinter better than most other cover crops. They’re a very good option for erosion control. They are also an affordable option for corn and soybean growers who are looking to rebuild their soil composition and fend off weed populations. Grasses are good for maintaining soil health and building organic matter versus other cover crops. Grasses are also a great forage option for livestock. (Examples: annual ryegrass, perennial ryegrass)
Grains are capable of surviving cool weather, some even through the rough winter months. They’re fairly affordable for growers, making them a common option throughout the Corn Belt. They help maintain the nitrate supply in fields and produce good biomass, which helps suppress weeds and build up soil composition. Grains are also good at catching nutrients in the soil. (Examples: winter rye, wheat, barley)
Legumes produce deep roots that generate good biomass. They are known to provide nitrogen and other beneficial nutrients. They also attract pollinators and other insects that are beneficial to crops. While they aren’t considered the hardiest crop, some legumes can overwinter. Legumes can also be interseeded with crops, meaning they can be seeded into the soil with crops that are already fully matured. Legumes can be mixed with other cover crops such as grasses and grains. There are several varieties that are good for grazing. (Examples: clover, hairy vetch, alfalfa)
Brassicas are deep-rooted cover crops that help reduce soil compaction and provide biomass to help suppress weeds and retain nutrients. They are considered “nutrient scavengers,” making sure the good nutrients stay put. While the deep roots have some benefits, in dry soils, brassicas are not typically recommended. They are better suited for fields where compaction is a concern. (Examples: tillage radishes, turnips, mustard)
Benefits of Cover Crops
Soil erosion has negatively impacted growers for years. It’s problematic for a number of reasons, but for growers, it’s top of mind when considering what’s needed for the next planting season. Soil erosion takes away the vital nutrients necessary for crop growth — nitrogen, phosphorus and potassium, to name a few. The cover crop acts as a barrier, protecting the soil and its nutrient makeup from heavy rains. Cover crops help hold the nutrients in place so they’re available for next spring’s cash crop. Cover crops also benefit area waterways by preventing phosphorus and nitrate runoff.
Soil composition can be improved through the use of cover crops. Cover crops increase organic matter in the soil, which in turn helps the soil be better equipped to retain water and prevent nutrient runoff. This could mean fewer costly fertilizer applications for growers throughout the growing season.
Weed control is always a concern for growers. Cover crops can help by competing with weeds. When planted in the same field that has experienced heavy weed pressure, cover crops compete for nutrients and other elements necessary for crop vitality, helping suppress weeds and potentially reducing the need for herbicide applications.
Grazing is a benefit of cover crops for growers who have livestock. Because many grasses and legumes are able to overwinter, they provide feed for cattle to forage through the winter months and beyond. Clovers and ryegrasses are good options for grazing.
Application and Timeline
Timing recommendations for cover crops vary depending on the method of application. According to the United Soybean Board, it’s important to allow cover crops at least 60 to 90 days of growth before winter begins. You don’t want to plant cover crops too early because you run the risk of the cover crops competing with cash crops for nutrients, water, sunlight and other elements necessary for their survival.
For interseeding applications, experts recommend aerial or broadcasting applications in late August to early September. In soybeans, this should take place roughly around 50 percent leaf yellowing to 50 percent leaf drop. One benefit of interseeding with soybeans is that when soybean leaves drop, they make a nice mulch for the cover crops.
The timeline for broadcasting or drilling cover crops after harvest depends on when harvest is complete. Cover crops need time to emerge and grow before winter starts, so this method may be successful only if you’re able to get into the field by late August/early September.
Eradication
Eradication is a vital (and final) step in the cover crop process. Growers need to eliminate the cover crop from their fields before their newly planted cash crop is forced to compete with the cover crop for nutrients.
Eradication can be completed before or after planting. Eradication can be completed with a herbicide application that simply kills off the cover crop before the new crop is planted or emerges. Depending on the cover crop, growers may be able to eradicate the crop through tillage or mowing.
Sustainability Cover Crop Initiative
For the past three years, Stine has collaborated with Peoples Company — one of the nation’s leading providers of land brokerage, management, appraisal and investment services — to offer land owners a paid-in-full cover crop program called the Sustainability Cover Crop Initiative. Through this collaboration, it’s possible to not only protect environmentally sensitive acres but also maximize yield on productive acres and improve overall return on investment through the use of cover crops. Learn more here.
For more information on cover crops, contact your local Stine agronomist or university extension experts.
Resources and Citations:
Cover Crops (USDA-NRCS)
https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1081555.pdf
Iowa Cover Crops: Answers to 8 Common Questions (Iowa Farm Bureau)
https://www.iowafarmbureau.com/Article/Iowa-Cover-Crops-Answers-to-Common-Questions
Why You Should Consider Cover Crops for Your Farm (United Soybean Board)
https://www.unitedsoybean.org/article/why-you-should-consider-cover-crops-for-your-farm