Buckwheat Cover Crop Handbook
Guidance on procedures
Step 1. Loosen soil
Vegetable production leaves the ground too hard for no-till seeding to work. The fine roots need some friable soil volume and percolation below the seed row to grow fast enough to suppress weeds. Incorporating the crop residue may be enough tillage to prepare the ground; plowing is not needed.
Buckwheat should be part of an overall soil-improvement program. Vegetable ground is often over-worked; preserve as much existing soil condition as possible by tilling no more aggressively than is necessary. Over-tilling is expensive and counterproductive.
Step 2. Wait before sowing
Sowing immediately after incorporating fresh organic matter can result in greatly reduced stands, either from seed rot or predation. A week is a sufficient delay after incorporating pea or bean residue in the summer.
It is also worth waiting if a heavy rainfall (an inch or more) is predicted. Buckwheat seeds are susceptible to rot if the soil is water-saturated even for a few hours. The reduced stand and slower growth can make weed suppression fail.
If the soil is very dry, irrigate a few days before sowing. There does not need to be much water to have a good effect on both the speed of germination and the lack of gaps.
Step 3. Sow
Choose the method that will work best for you, and carry it out carefully. Sloppy or uneven planting will cause the stand to fail.
Drill or broadcast. A solid stand is essential for suppressing weeds. Weeds tend to grow in gaps more than 8 inches across. Seven-inch drilled rows allow the use of a minimal seeding rate of 50 lb per acre. For broadcasting, an increased rate (70 lb/ac) is recommended to get minimal coverage in the thinner spots. The rate can be adjusted if the uniformity is better or worse than average. Broadcasting is faster, so the savings in time and fuel may offset the higher seed cost.
Rapid emergence is essential for weed suppression. Seedlings emerge faster with shallow seed placement. The shallowest setting that reliably covers the seed is a good target. With a drill, 3/4 inch is reasonable if there are few clods. For broadcasting, some growers have found that a heavy chain or the back side of a drag harrow work well to cover the seed. A disk is usually too deep and works the soil more than necessary.
Step 4. Killing and volunteers
Most growers find that buckwheat volunteers are not a significant challenge the following season, and that they are eliminated by normal practices. However, others have had trouble, especially when the volunteers go to seed.
Timing is important for avoiding volunteers. Seeds begin to appear about six weeks after sowing. The crop will just be coming into full bloom; on vegetable ground it is generally about 30” tall. Don’t let the plants mature in the fall unless you have a plan that deals with the seeds that are produced.
There are three steps to avoiding problems. First, minimize seed production. Second, minimize winter survival. Third, kill seedlings in the spring.
- Minimize seed production with timely and thorough mowing. Some bigger plant parts may survive, for instance in the wheel tracks. Even though they are severed from the plant, some seeds on them will mature. There can be a small amount of regrowth from lower nodes that produces a few seeds. Incorporate immediately if there are immature seeds.
- Reduce winter survival by leaving mature seeds on the soil surface. Exposed seeds tend to survive less than those that are buried by fall tillage. Some volunteer seed on the surface will germinate in fall rain, but are then killed in the first frost. Animals and fungi also consume seeds over the winter.
- Spring seedlings appear in mid-May. They are effectively controlled by tillage, cultivation and by low rates of many common herbicides.
Some growers plan on two successive stands of buckwheat, with the second stand reseeding from the first. Others allow the grain to mature, and harvest it with a combine.
Many herbicides used on the subsequent crop will eliminate buckwheat volunteers. Some that have little effect on buckwheat are Dual Magnum, MCPA, Microtech, Outlook and Prowl. If you use these exclusively, an additional control will be needed.
Step 5. Prepare for the next crop
Getting the most value out of the buckwheat cover crop depends on taking advantage of what it has done. The cover crop will leave the ground with few weeds and will deplete weed seeds. The soil will also have improved aggregate structure.
Weed control is best continued with a winter smother crop and timely tillage in spring. These practices stimulate weed germination and kill seeds, but prevent weed seed production.
The aggregates that have formed will allow more timely operations in the spring and better crop growth as long as they are not destroyed. A grass cover crop will protect and stabilize the aggregates by keeping the soil covered and secreting glue-forming compound from the roots. Work the ground in spring when the soil moisture is appropriate to keep the aggregates intact.
Rye is the classic overwintering cover crop (but also consider triticale or wheat). Oats or fall mustard serve well as winter-killed cover crops.