Making CRP productive cropland
Conservation Reserve Program (CRP) acres are fields that private landowners put into conservation for 10 to 15 years to reduce soil erosion, improve water quality and/or to improve the environment. Landowners are paid an annual government rental payment in exchange for keeping acres in permanent vegetation. In 2020, Ohio had about 49,300 acres of expiring CRP acreage with about 34.7% or 17,123 acres that went back into crop production. Indiana had about 98,700 acres expire and 34.6% or 34,200 acres converted to crop production. High grain prices tend to cause more CRP acres to leave while low grain prices increase CRP sign up.
Landowners usually put their worst performing or “worn out” cropland into CRP. Some land is Highly Erodible Land (HEL) with severe soil erosion, poorly drained or just hard to farm. These fields tend to have low soil fertility, poor soil structure, poor soil health and overall low crop productivity. On hilly land, gully erosion, lost topsoil, and exposed subsoil creates less productive soils. These fields have less soil organic matter (SOM) and tend to seal over, so standing water and poor drainage make it difficult to raise crops profitably. Sometimes irregular shaped fields close to winding streams or ditches are placed in CRP to make farming easier.
After 10 to 15 years in permanent vegetation, many CRP fields become quite productive (at least for a while) after having been “rested” or “protected” due to improved soil health. Often SOM increased with darker soil color changes noticeable leading to better soil structure (soil crumbles). Sometimes drainage is improved due to deep roots breaking up compacted soil layers. How long this land remains productive depends on how the land is managed after it comes out of CRP.
Typically, most farmers worry about the “thatch” — uneven soil, weeds and insects. Farmers often burn off heavily matted or thick vegetation and till or plow to even the soil. Tilling releases many stored SOM nutrients and improved soil structure allows for higher crop yields for a few years. Corn is often planted first with extra insecticides and fungicides followed by soybeans. After a few years, the soil starts to deteriorate quickly as SOM is burnt off. The CRP soil will start losing its color, become harder to farm and start to seal off. Before long (three to seven years), a restored productive soil is back to performing poorly again.
Some no-till farmers are trying a different approach. Their goal is to maintain the improved soil structure and improved soil health by maintaining it. One strategy is to buyout the CRP contract one to two months before it expires in October. Buy out the CRP contract in August, mow the field and try to plant a cover crop to main soil diversity. Soil tests are taken, but may be confusing. Organic and plant available microbial nutrients may not always show up on soil tests designed to measure inorganic nutrients. SOM levels and the carbon to nitrogen (C:N) ratio needs to be monitored. High C:N ratios favor soybeans, low C:N ratios favor corn which have more nitrogen available. In healthy soils, more N is tied up by soil microbes, so corn benefits from 40 to 70 pounds of actual N up front at planting, especially if the C:N ratio is high (above 25 C:N ratio). The microbial population doubles with every 10-degree Fahrenheit increase in soil temperatures. The mineralization of N from soil microbes may be slow in the spring until soil temperatures warm up and corn is a heavy N feeder.
Most farmers plant soybeans one to two years with a cereal rye cover crop followed by wheat, barley or oats and then a multi-cover crop mix with legumes, clovers and pollinators before going to corn. Fields should be scouted for insect pests and beneficial predators. Beneficial insects like ground beetles, lightning bugs, Rove beetles and spiders may reduce the need for insecticides. Insecticides are deadly to beneficial predator insects. Many beneficials insects need a flowering pollinator to complete their life cycle. Sometimes a field may need leveling in some places, but the goal is to minimize any tillage. Tillage burns up SOM but also buries and preserves weed seed that the beneficial insects need to survive. Mycorrhizae fungi (150 to 200 species) thrive in undisturbed soils and restore soil productivity. Once a soil has healed and becomes productive again, it’s important to try to maintain that soil productivity for many years.
Correction: The Ohio H2O program for manure application allows cover crops to be hayed or grazed.