The unfortunate scenario of consistent, excessive moisture events across South Dakota and many parts of the Midwest is causing some farmers to accept the fate of wet fields or prevented planting acres.
However, this scenario leads to an ideal time to invest and begin rebuilding soil aggregates and structure for next year and beyond with cover crops. And it’s an opportune time to discuss sharing this cost with your landowner, because it will help improve the soil and grow their investment.
The top 5 reasons why you (and your landowner) should invest in cover crops:
1. Save applied nutrients. A diverse, multi-species cover crop mix will capture and save applied-nutrient (and dollars) investment. Already applied nutrients can be released to subsequent crops through mineralization.
2. Eliminate bare, weedy soil without tillage. Keeping soil covered with a diverse cover crop mix will stop the destructive nature of tillage to the soil. You can build soil structure, reduce wind and water erosion, and keep nitrates at home to improve water quality. Next spring, these acres of cover crops offer the great opportunity to experiment with no-till, even plant green without the need for tillage, to continue building soil structure.
3. Reduce erosion. NRCS staff recently visited a variety of unplanted fields to show perspective of erosion loss due to excessive water. For example, one 157-acre field (Site #15) showing ephemeral gully erosion was losing 1,073 total tons or 6.8 tons per acre. That is the equivalent of 71.5 dump trucks full of soil leaving the field. Site #14 shows a loss of 11.8 tons/acre, and that soil volume would fill a 48-ft diameter grain bin that is 8 rings high.
4. Control weeds. Instead of relying solely on herbicides and tillage, cover crops can reduce weed populations because they will shade the soil to suppress weed growth and subsequent weed seed production. The goal is planting a cover that you want which will prevent too many annual weeds from going to seed. Summer annual crops like sorghum-sudangrass, forage sorghums, pearl millet, sunflowers, buckwheat and cowpeas can form a dense canopy to out-compete weeds.
5. Repair saturated or unplanted soils. Soils with no living plant roots for lengthy periods have a reduction in arbuscular mycorrhizae (AM) fungi. These beneficial fungi form important relationships with plant roots aiding the uptake of nutrients, especially phosphorus (P). Fallow syndrome (P deficiency) occurs in plants when no crop is grown during the previous growing season. The best solution to prevent fallow syndrome is to rebuild and increase AM fungi in the soil by growing a living root and greatly reducing tillage (no-till). Cover crops can provide the living roots during periods when cash crops are not grown. Living roots, increased AM fungi levels, and greatly reduced tillage (mostly no-till) will increase soil aggregation and pore establishment--very important for improved water infiltration, air exchange and soil strength (increased load bearing capability).
Before selecting cover crop species, make sure you understand the herbicide impact on the types of cover crops you want to seed.
Which cover crops should I plant?
Select a cover crop based on your crop objectives, management ease for your operation, soil characteristics, crop rotation, cost, and residual herbicides that might be in the soil. Options include oats, cereal rye, sorghum-sudangrass, sudangrass, oilseed radish, peas, red or crimson clover. Each species can provide different attributes, and often a mix of species — given a long spring through fall season to grow — allows for deep rooting and more nutrient capture. A combination that includes grass, a legume, and oilseed radish provides the best overall soil improvement and helps alleviate compaction.
What are the best management practices for cover crops?
The NRCS South Dakota has an excellent, free spreadsheet resource for download that offers cover crop seeding plan and record, cover crop species ratings, recommended cover crop mixes, and aerial seeding strategies. There is also a Resources for Cover Crops in South Dakota page (https://bit.ly/SDCoverCrops) that examines species selection, forage selection, profitable management, grazing, and more. SDSU Extension has a cover crop web page with excellent information. When seeding cover crops into crusted, hard topsoil that occurs with prolonged soil saturation, use a drill or planter to achieve good seed to soil contact.
For additional information, see your local USDA NRCS for a free, one-on-one on-farm consultation about cover crops (not insurance) or read Delayed Planting Challenges: Cover Crop Considerations by Sara Bauder and Ruth Beck, SDSU Extension agronomy field specialist, Anthony Bly, SDSU Extension soils field specialist, and Warren Rusche, SDSU Extension beef feedlot management associate.