Arkansas study shows cover crop soybeans are 10.5% more yielding
A three-year study conducted by the Arkansas Agricultural Experiment Station shows that catch crops can improve soybean field yields. The study also answers an open question about wheat double crop systems.
The cost of a cover crop system is comparable to a traditional tillage and no cover crop system because tillage is removed from the equation, according to Trent Roberts, associate professor of soil fertility and testing for the experimental station and soil specialist for the Cooperative Advisory Service.
Roberts is the Endowed Chair of Soil Fertility Research at the University of Arkansas System Division of Agriculture and lectured on the study of cover crops and soil health in soybean rotations at Arkansas Rice and Soybean Field Day Online 2021.
“When we use catch crops, we can only really get their full benefit from the production system if we also implement no-till practices at the same time,” said Roberts.
No-till saves about $ 30 to $ 60 per acre in labor and fuel costs associated with tillage, depending on the equipment and the number of passes used, he explained.
“It’s a very substantial cost that often pays off more than catch crop seeds, planting, and at least some of the termination costs,” said Roberts.
The study compared soybeans grown in fallow fields with those grown after wheat for grain in a dual crop system and those grown after a range of catch crops such as corn rye, black oats, barley, and Austrian winter peas. The researchers also used a 50/50 blend of Austrian winter peas and a “soybean blend” that included grain rye, beets, and purple clover.
The fields with the highest soybean yields were after no-till, chemically terminated catch crops, with a three-year average of about 63 bushels per acre. The best cover crop for soybeans was the 50/50 mix with Austrian winter peas and a “soybean mix,” noted Roberts.
The fallow fields produced about 10.5 percent fewer soybeans, with a three-year average of about 57 bushels per acre.
THE WHEAT DOUBLE-BENEFIT QUESTION
Roberts noted that he often receives questions from growers about the profitability of the double crop system. Knowing that there is a strong correlation between soybean planting date and yield potential, producers have wondered how much yield is lost in Arkansas if you wait for the wheat harvest before planting soybeans, he said.
The study showed that soybeans grown immediately after a wheat harvest produced an average of 53 bushels per acre due to later sowing. However, the revenue from the wheat crop could offset the loss of soybean yield despite the additional inputs, Roberts said.
There are “no statistical differences” in the economic returns of the double crop system compared to some of the higher yielding cover crop systems, Roberts said.
The highest yields are seen with most cover crop treatments, he added, but they are also very high in the dual crop wheat systems.
“The wheat double crop system can be profitable,” said Roberts. “You will lose the yield of your soybean by sowing late, but often the value of the wheat crop that we can grow in the meantime offsets any possible loss of yield that we see in the soybean.”
The economic yield analysis used an average of the soybean and wheat crop values over the past 10 years to capture potential fluctuations in commodity values over time.
SOIL HEALTH YIELD RAUSCH
When treating catch crops without tillage, researchers measured numerical increases in both soil health and soil organic matter, although Roberts said the increases are not statistically significant. Nevertheless, the soybean yields on the no-till areas with catch crops are improved.
Roberts stated that in many cases they see “the cumulative effects of increased infiltration, additional weed control, increased water retention and a decrease in evaporation” when they have catch crops. The US Geological Survey defines evapotranspiration as the sum of evaporation from the land surface plus transpiration from plants.
While not yet seeing a statistically significant increase in soil health, Roberts and other researchers believe that continued implementation of cover crop practices will result in significant increases or changes in soil health metrics over time.
For those new to greening, starting with a system that includes soybeans as a crop is a good start, Roberts said.
“They are very forgiving of the high sowing rates and the ability to sow or plant these high populations of plants,” said Roberts. “There is more flexibility when you have standing problems.”
Farmers should experiment with what works best on their farm to establish soybeans as catch crops, but transplanters or seed drills set up for no-till work best, he added.
“We have used a wide variety of planters and seeders to establish soybeans in both green and closed catch crops. The furrow closes properly,” wrote Roberts. “This is the battle of planting catch crops in no-till catch crop systems – covering the seeds and closing the seed pit.”
The U.S. Department of Agriculture’s Natural Resource Conservation Service has funding to start a cover crop program, Roberts said. Funding to cover seed and termination costs can typically help a farmer start catching crops on approximately 300-350 acres.
The Arkansas catch crop study was conducted at three locations to measure response to different environments and soils. These locations were at the Pine Tree Research Station near Colt in St. Francis County; the Vegetable Research Station near Kibler in Crawford County; and the Rohwer Research Station in Desha County.