Cover crops have benefits for grain production and graze-out systems
By Doug Rich
Cover crops that offer potential benefits to farmers highlighted a field day at the North Central Oklahoma Research Station in Lahoma, Okla., on Aug. 29.
Jason Warren, assistant professor of Soil and Water Conservation and Management Extension specialist at Oklahoma State University, said 17 different species of grass and broadleaf plants were tested for cover crops. One of the goals of this research project was to see which of these plants would flourish in Oklahoma growing conditions. All of them were planted in May after the wheat crop was mowed off to simulate planting after the wheat crop was grazed off. In the interest of the cover crop research project, cool- and warm-season species were planted at the same time. A number of different mixes were also planted for evaluation.
The benefits of planting a pure stand of a particular species for a cover crop or a mix are yet to be determined. Warren said there are some studies that show mixes provide a greater level of benefits for the producer.
“A mix provides a more diverse system,” Warren said. “If you have a grass out there it will have a fibrous root system that will fill near the surface. A legume is primarily out there to generate nitrogen. I like a mixture of grasses and legumes because the grasses provide the residue that opens the ground up and protects the soil surface while the legumes replace the nitrogen that grasses pull out of the soil.”
Warren said he likes grasses for weed control, as well. There is also the potential for species such as buckwheat to attract beneficial insects. Central and western Oklahoma offer a tough environment for buckwheat, but Warren said he has seen very good stands of buckwheat in eastern Oklahoma.
“The challenge is that of these ancillary benefits, outside of residue production and nitrogen production, are small effects that cumulatively together may impact the cropping system but individually are hard to quantify,” Warren said. “That is why we tell producers this is what we are doing; this is what we see, but take it to your farm and try a few acres and see what happens for you.”
Producers need to know what they want from cover crops before they are planted. Do they want cover crops that fix nitrogen in the soil, or do they want cover crops that produce residue to protect the soil and increase organic matter?
Kevin Meeks, an OSU graduate student, reported on the summer cover crop rotation study at Lahoma. This plot was planted a month later than the cover crops in the first stop on the tour. Meeks said they to hope find out which cover crops have a positive effect on winter wheat production.
The cover crops in this study will be cut the first week of September, and biomass and protein levels will be collected on each plot and core soil samples pulled to evaluate moisture differences. Winter wheat will be planted on these plots Oct. 15.
One reason they record biomass production is to determine grazing potential on cover crops. Warren said he is glad to see that grazing cover crops is not as taboo as it once was in many areas.
“I would rather see them grazed than used for hay production, because if it is grazed you are not taking much out of the soil but if you cut them for hay you are taking all the nutrients off,” Warren said. “Grazing can be managed to keep some residue on the surface.”
Warren said there is a place for cover crops if a producer is growing wheat for grazing or just for grain production.
“For anybody who has heavily grazed out wheat, I think there is a greater potential for cover crops in a graze-out scenario than I do in a grain-only scenario,” Warren said. “If you are grazing out year after year, you will have limited residue and the cover crops can be planted earlier because you don’t have to wait until the grain comes off. You can plant them in May when the cattle are off. This gives you a longer growing season for the cover crops.”
“What cover crops provide for you, particularly if you have a cow-calf operation, is potential grazing in the summer or potential grazing in September if you are starting some stocker calves,” Warren said.
Most of Oklahoma and the High Plains are just coming out of an extended drought. A point of contention for many producers is whether or not they are sacrificing valuable soil moisture to grow cover crops. Warren noted that any green growing crop pulls moisture out of the ground, but with cover crops a producer decreases or eliminates evaporative water loss.
“What we have seen is if you have a chemically fallowed no-till system where there is stubble to protect the surface, we can slow the rate of evaporative water loss but we can’t stop it,” Warren said. “With cover crops our thought is that instead of letting the atmosphere take that water we should put it through a plant and grow biomass or grow nitrogen.
At the end of the cover crop field day Warren suggested that producers try a few acres of cover crops on their own farms and see for themselves if it works on their soil and in their cropping system.
Doug Rich can be reached by phone at 785-749-5304, or by email at firstname.lastname@example.org.