More farmers are showing interest in and using an approach called bio strip-till, where specific cover crops are planted in individual strips after the harvest of an early season crop.
Goals for using this approach typically include a combination of (1) creating a dark strip in the field with residue to simulate strip till, (2) opening up the soil for cash crop root growth, (3) to keep competitive winter annual species like cereal rye out of the cash crop planting row, and (4) residue management to keep problematic residue out of the planting strip.
Here are examples of bio strip-till of varying complexity being used by farmers in North Dakota:
In Northwood, N.D., radish (2 pounds per acre) was planted into wheat stubble on 30-inch row spacing in a field going to soybeans the following year. Soybeans will be planted on the radish residue. The goals are to create a black strip in the wheat stubble and channels through the soil for soybean roots to follow. Within two months of seeding, radish roots extended at least 10 to 11 inches into the soil (roots often extend deeper than what we dig/see because tap roots can break off). Research has shown that soybean roots will use existing root channels as pathways to get into the subsoil, especially when they encounter a compaction layer that the cover crop was able to penetrate.
In southwest Grand Forks County, N.D., cereal rye (30 pounds per acre) was planted on 30-inch rows, and radish (2 pounds per acre) was planted between cereal rye strips on a field going to edible beans the following year. The edibles will be planted on the decomposed radish strips. The primary goals are to create a dark strip in the spring with the radish residue and to keep the competitive cereal rye away from the planting strip for edibles. Keeping the cereal rye away from edible beans can help, however monitoring and timely termination are still required in the spring.
In Rutland, N.D., radish (3 pounds per acre), turnip (1 pound per acre) and flax (4 pounds per acre) planted on 30-inch rows, and faba bean or field pea (80-100,000 seeds per acre) were planted between radish rows on wheat stubble in preparation for a corn crop the following year. Corn will be planted on the radish/turnip/flax rows. Goals for this approach include black strip (residue from radish/turnips) at the time of planting corn and also getting the pea residue away from the strips to avoid tangling around the planter. This approach plus residue managers has worked well for warming up strips for corn.
These examples should be used as a starting point and adapted to on-farm conditions. I am consistently impressed with the ways farmers innovate with cover crops - new approaches are being modified and tested each year. Much of this information is being posted on the NDSU Soil Health webpage or you can follow me on Twitter (@NDSUsoilhealth) to get timely tips.