By James Hoorman, Hoorman Soil Health Services
After being on the road teaching (Iowa, Pennsylvania), I am home recovering from COVID. Here are the last 15 tips from my factsheet: “25 Tips to Growing and Managing Cover Crops”.
Tip 11: Soil Microbes (especially bacteria) are like soluble bags of fertilizer and directly feed plant. There is about 1000-2000X more soil microbes associated with live roots than bare soil. Plants supply 25-45% of their total carbohydrate root reserves to feed soil microbes which retrieve soil nutrients more efficiently than plant roots hairs. Bonus: Beneficial microbes love sugar in small amounts, so add 1# sugar/Acre to nutrient, herbicide, fungicide spray applications.
Tip 12: Use grasses with fibrous roots (cereal rye, oats, barley) before soybeans to maximize phosphorous uptake. Cereal rye controls weeds through competition for light and nutrients, allelopathy (natural herbicides in stem and leaves), and reduces diseases by keeping the soil drier due to transpiration (loss of water to the atmosphere).
Tip 13: If soil is too wet in the spring, let cover crops grow to dry the soil. If soils are starting to dry out, terminate the cover crop sooner and plant as soon as possible. Planting green is a good option but requires sharp disc blades.
Tip 14: Let cover crop roots decrease soil compaction and improve soil structure. Generally, it takes 2-3 years, but soil structure improvements will be more permanent with cover crops than doing tillage which destroys both soil organic matter (SOM) and soil structure.
Tip 15: Use cover crops to increase SOM, to protect the soil from erosion, and to improve nutrient efficiency. Each 1% SOM is associated with 1000# N, and roughly 100# of P, K, and S in the soil. The majority of the SOM comes from the roots, so growing two sets of roots (regular grain crop plus your cover crop) greatly increases SOM accumulation.
Tip 16: Plan to add 100-150#N in fertilizer, manure, or grow a legume cover crop to decompose the additional 0.1 to 0.15 yearly increase in SOM from cover crop roots. Soil microbes feed first, SOM residue ties up N second, and generally, corn roots feed third.
Tip 17: Use a shovel to check for poor soil structure, compaction, and unnatural soil layers. Good healthy soil should crumble in your hand. In good soil, you should be able to push the shovel easily into the soil (even on our clay soils). Use an undisturbed fence row as a reference to compare soil structure changes due to tillage.
Tip 18: Water requirements for corn double with every 10 degree increase in temperature. At 75 degrees F, corn needs 1 acre-inch of water per week, at 85 degrees F, 2 acre-inches, and at 95 degrees F, 4 acre-inches of water per week. Each additional 1% SOM increases your soil water holding capacity by .5 to .8 acre-inches of water per foot of soil.
Tip 19: Allelopathic effects come from cover crop leaves. To minimize problems before corn planting, cut or harvest above ground biomass to reduce toxins and add manure or nitrogen fertilizer to decompose these toxins. If you cannot harvest it; kill it early, and wait three weeks to plant corn OR plant green and wait to terminate cover crop when the crop is well established.
Tip 20: The best weed fighters are Sorghum Sudan grass, radish, and cereal rye; which out compete weeds for sunlight and nutrients. Avoid tillage which replants weed seeds.
Tip 21: Most corn and soybean diseases like Phytopthora, Fusarium, Phythium, and Rhizoctonia are associated with saturated soils. Use cover crops to dry out the soil and reduce disease pressure.
Tip 22: To increase predators for destructive insects, plant blooming cover crops that flower in the summer and provide nectar to developing predators (buckwheat; sunflower; hairy vetch; red, Crimson, or Balansa clover) and maintain surface residue for predator winter survival.
Tip 23: For forage production, use oats, cereal rye, and Sorghum Sudan grass. Fall planted oats with 50# N may produce 1-2 tons of forage before Christmas. Cereal rye plus fall and spring N may supply 4-5 tons forage in the spring (early to mid-May). Sorghum Sudan (SS) plus 100#N may produce 1-2 tons first cutting and 4-5 tons second cutting and increase SOM by 0.5-0.75% with one planting.
Tip 24: After wheat or corn silage, plant a cover crop to maximize sunlight capture. Apply manure in the fall and spring to maximize forage quality and quantity. Harvest the crop in the boot stage.
Tip 25 & Summary: Keeping soils covered with live plants mimics Mother Nature. Live plants supply the energy to keep soil microbes healthy, improve soil structure, and improves water quality .