Crop rotation and cover crops enhance the effectiveness of no-till cropping systems by reducing disease and weed pressure, improving soil moisture holding capacity and increasing soil organic matter content.
“It’s hard to think about no-till without crop rotation,” said Oklahoma State University graduate student Silvano Abreu at the No-Till Oklahoma Conference in Oklahoma City earlier this year.
“I have not seen no-till success without rotation,” he said. “Rotation promotes healthy soil and makes it more productive.”
He said wheat after wheat in no-till systems promotes weed and disease pressure. “Rotation to corn or milo breaks that cycle. Rotation helps manage weeds such as shattercane.”
Chad Godsey, OSU Extension agronomist, agrees. “Crop rotation offers a lot of benefits to no-till production, and we have several alternative crops and cover crops available. It’s important to maintain soil cover as much as possible to enhance soil quality. Growers need to maintain flexibility with crop options.”
Godsey said one criticism of using winter cover crops is potential moisture loss. “It takes only one rainfall to replenish moisture lost to a cover crop,” he said. “That’s usually adequate.”
Southwest farmers have several rotation and cover crops available. Abreu said ryegrass planted after harvesting cotton helps protect soil over the winter and also produces biomass and soil organic matter.
“With a single crop it’s hard to break down soil compaction. Rotation provides different kinds of root systems that help break compaction layers.”
He said continuous cotton produces very little biomass. “Adding a cover crop increases biomass significantly. Austrian winter pea, for instance, grows rapidly, to 4 inches tall in just a few weeks.”
A combination of a forage radish and oats also provides significant benefits as a cover crop, producing as much as 4,000 pounds of biomass per acre. “The forage radish increases water infiltration potential,” Abreu said. “The plant dies with cold weather but the big roots remain in the soil. Those roots are 85 percent water and as they decompose they release moistures into the soil.”
Godsey said the oats decompose slower and maintain live plants longer than the radishes so the combination keeps live vegetation on the soil for much of the winter.
Abreu said pigeon pea produces 4,000 pounds of biomass per acre. Sun hemp is another possibility and helps break down compaction.
He said corn also produces a lot of biomass, more than 10 tons per hectare. Oats produce nearly 7 tons; wheat adds 4.6 tons; turnips 4.4 and soybeans 3.7.
He said turnover rate, the time it takes for vegetative matter to turn into soil organic matter, is fairly short in the South. “Most organic matter decomposes quickly with more than 80 percent decomposing within three months after a crop dies. So soil can run out of protection quickly. Producers need to keep organic matter in the system longer by producing more biomass to protect the soil.”
Organic matter also contributes nitrogen to the soil. “A cover crop such as cowpeas or white clover can add as much as 40 pounds of nitrogen per acre.”
Godsey said short fallow periods also may help increase water holding capacity.