SPEND TIME with veteran no-tillers and you quickly learn not to discount the importance of cover crops. In fact, they're key to the whole operation. Without good cover crop management, the conservation tillage system can be hamstrung.
That fall-planted cover crop makes the residue that you'll plant into next spring. It takes about a 30 percent residue cover level to give even minimally effective erosion control.
“Managed properly, a cover crop can reduce erosion, aerate the soil and maintain higher moisture levels, all of which help to ensure good soil for planting next spring. The added residue and coverage provided by cover crops is vital to low-residue crops such as cotton and soybeans.
Cover crops also provide food and cover in winter months for earthworms, soil microbes and wildlife. They also add organic matter and tilth to the soil and keep the surface particles from running together and/or ‘baking out’ in late spring,” says John Bradley, Monsanto's conservation tillage specialist.
In addition, a good cover crop's residue can keep soil cooler in early summer, reducing moisture loss and improving the environment for root growth. After terminating the cover crop in spring, its decaying roots leave macropores that aid water filtration. Plus, as the crop grows, the residue protects seedlings from wind and sandblasting.
So, if conservation tillage will figure into your plans next spring, spend time this fall making sure you get a good cover crop in the ground. First, choose one that helps accomplish your main objective. That could be preventing erosion, conserving moisture, or producing organic matter.
The best cover crops to consider are generally wheat, rye, oats and legumes.
“If you're growing continuous cotton, I recommend growing wheat during the winter. It doesn't get too tall to manage, has good winter hardiness, is relatively inexpensive and has rapid growth,” Bradley says.
Rye, which can be grown over much of the South, has its own advantages. “It is cold-tolerant, suppresses nematodes and certain weeds and grows rapidly. However, rye seed costs more than wheat seed, and rye can produce too much biomass,” Bradley says.
Both wheat and rye can stand fairly late planting in the fall, and canopy quicker than legumes. Oats is less cold tolerant than wheat and rye.
Be careful if you decide to go with a legume like hairy vetch and crimson clover. They add nitrogen to the soil but that extra nitrogen can also delay cotton maturity the next fall. Cover crops like Austrian winter pea and vetch are usually harder to terminate than wheat and rye. Legumes usually cost more to grow, as well, and can be tougher to manage.
Long-time strip-tiller Lamar Black prefers rye as the cover crop on his Millen, Ga., farm and uses it on the whole farm except for fields where he double-crops soybeans behind wheat. He now manages that heavy rye residue by terminating it and then using a heavy tractor-mounted roller to flatten the residue on the soil.
“I like to have that heavy residue. Really, the heavier, the better, once you learn how to plant through it. That residue is what gives you all the benefits of improving the soil and retaining moisture,” Black says.
Max Carter, a veteran no-tiller at Douglas, Ga., plants about half his acreage in wheat and the rest in rye. “I graze the rye. I don't do it the way Lamar does his. What I plant also depends on the availability of the seed and the prices I expect. I'm harvesting my winter crop, so I have a little different philosophy on it than Lamar does. Everything I do is double-cropped,” Carter says.
Be sure to plant cover crops early enough to be well established before cold weather. They'll need to develop a canopy and as much biomass as possible. Get them in the ground too late, and they won't mature enough to do an adequate job.
“If you use a no-till drill, plant the cover crop immediately after harvest. In cotton, cover crops can be seeded when defoliating by airplane or with a cyclone seeder on a tractor or high-boy. Wheat, rye and oats can be seeded by air. If you're intent on doing some fall tillage, you can also seed cover crops when you disk. If you do any tillage in the fall, I strongly suggest the use of cover crops,” Bradley says.
Avoid high-seeding rates for cover crops. That can cause them to use too much moisture and delay spring planting. Bradley recommends wheat be seeded at 60 to 90 pounds per acre, rye at 45 to 60 pounds per acre, and crimson clover and hairy vetch drilled at 15 to 20 pounds per acre. Some experts in the “southern” part of the Sun Belt recommend lower rates of wheat.
Fall is also a good time to control tough problem weeds like johnsongrass, bermudagrass and vines. “Twenty-six ounces of Roundup UltraMAX™ herbicide per acre applied prior to heavy frost aids greatly in the control of perennial weeds for the next season,” Bradley says.
In spring, it's best to burndown the cover crop 2 to 3 weeks before planting the summer crop. “The best way to kill cover crops in the spring in a no-till or con-till situation is to spray with a burndown herbicide such as Roundup UltraMAX. It will help warm and dry the soil, and if done in a timely manner, will minimize the damage from insects present in the crop,” Bradley says.
That cover crop residue, then, will help control early-season weeds as well as reduce erosion and water loss.
Think of the cover crop and the cotton, corn or soybeans, which follow as parts of a single system designed to build and protect soil and produce profitable yields. “Planting a cover crop means a little more work in the fall, but you'll be glad you did it in the spring,” Bradley says.