Southwest farmers planning to seed a cover crop for winter grazing or as a hedge against soil erosion through the winter and early spring should get seed in the ground soon.
“Plant cover crops as soon as possible,” says Texas A&M AgriLife Research Soil Scientist Katie Lewis, Lubbock. “Plant as soon as possible after harvesting the summer crop.
“And if you have nothing in the ground because of failed acres or early harvest, plant now. It may be hard to establish a winter cover crop after cotton harvest and before the first freeze."
Lewis recommends planting following a recent rainfall, which is prime for establishing cover.
Texas A&M AgriLife Research Soil Scientist Katie Lewis (Photo by Shelley E. Huguley)
Southwest farmers have numerous options for winter cover crops but Lewis says they should consider the overall goal for the cover, field and climate conditions, and whether the crop will be grazed.
“Our most common winter cover crop options are wheat and rye. We are seeing more forage sorghum planted for summer cover. Farmers are baling it then letting it grow to keep something on the ground until winter kill.”
She adds that cover crop mixes that include turnips, radishes, and legumes like Austrian winter pea are “hit and miss.
“Small grains do best, produce the best biomass, and cover to reduce erosion. With mixed species, establishment is not as good. If mixes are seeded early and are well established, however, they can be effective. Another factor is the seed in mixes is expensive.”
Moisture matters. “Last year, my husband, Clay, planted a lot of cover on failed dryland cotton. He planted cover earlier on failed dryland acres, but it was so dry, the cover didn’t make it, blown out by wind and dry conditions.”
Lewis says some question planting cover on dryland acres. “I recommend it on all acres but establishment on dryland is uncertain because of our climate.”
She says a key to cover selection and planting time is ensuring the cover crop has time to produce sufficient biomass before terminating ahead of the summer cash crop per your goal (e.g., reduce erosion). “Producers will want to shut down water usage in the cover crop to align with spring rain and to make up the moisture deficit from the cover crop.
“But if we don’t have the water, the cover crop will not grow; pretty simple.”
Lower seeding rates
Reducing seeding rates for winter cover offers an opportunity to reduce costs without sacrificing biomass production, Lewis says.
“We have found in studies over the last four years that reducing seeding rates from 60 pounds per acre to 30 pounds per acre will produce as much biomass. We can cut production costs in half.
Conventionally tilled rows (left) and cover (right) are from a continuous cotton system (without and with a cover crop). (Texas A&M AgriLife, AG-CARES)
“I have heard some concerns about a lower seeding rate, fearing that January rain and wind could decrease stands. We would hope by that time, the cover will be well established. Also, leaving cotton stalks standing will help reduce damage from blowing sand. Growers still need to cut stalks before the cover gets too tall, but they can leave them standing into the new year.”
Lewis says producers typically rely on residual fertilizer to establish a cover crop and do not apply herbicides.
“Make sure the cash crop following that cover gets adequate nutrients,” she adds.
“In our semi-arid environment, we can have limited nitrogen availability due to immobilization early in the cash crop growing season because the cover crop produces so much biomass it stimulates microbial activity. That limits nitrogen and phosphorus availability for the next growing season.
“For the most part, especially with a grass cover crop (wheat or rye), root systems reach down far enough that they help pull some residual nitrogen from deeper in the profile and cycle it up through the soil surface.”
Cover crop, fallow rotation
Lewis says several cover crop options have a place in conserving soil and improving soil health. Her favorite is a cotton, wheat, fallow rotation.
“That system has never failed to produce one-and-a-half times as much cotton as we get following a cover crop,” she says. “Nitrogen availability is a factor.
“If we keep everything equal across various systems, rotation will outperform the others,” she says. “Will Keeling, Texas AgriLife economist, says the reduction in input costs makes a difference. It’s not necessary to produce enough cotton to make up for the fallow period, but considering the lower input costs, producers can make as much money as with continuous cotton systems.”
Producers using the cotton, wheat, fallow rotation also see benefits to the soil from the wheat residue that increases water holding capacity.
She says the cotton, wheat, fallow rotation is the most sustainable system in situations with limited irrigation.
A wheat, fallow, cotton system offers Southwest farmers a production system that provides winter cover and residue that improves soil health and water holding capacity. (Texas A&M AgriLife, AG-CARES)
“A fallow system throws people off,” Lewis says. “However, they still harvest a crop each year, but with a nine- to ten-month fallow period. The system provides substantial cover to keep soil from blowing.”
The rotation offers other benefits, including limiting root knot nematode populations and improving soil health — both biological advantages and increased water-holding capacity, she says.
“I understand that landlords often do not want to grow anything other than cotton, which means diversification will be including a cover crop. We need to optimize cover crop strategies, including reduced tillage, winter cover, and terminating in a timely matter.”
Lewis adds that long-term rotation is the better option. “We are working on other crop rotation alternatives.”
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