Schultz Bruce, Blanchard, Tobie M., Gould, Frances I.
Josh Copes, LSU AgCenter agronomist and weed scientist, inspects soybean plants at the LSU AgCenter Northeast Research Station. Photo by Bruce Schultz
LSU AgCenter scientists are working to determine how winter cover crops grown in the offseason can be used to help farmers improve yields, reduce expenses and enhance soil health.
Changyoon Jeong, LSU AgCenter agronomist, is studying the potential for rapeseed to provide protection against nematodes in soybeans. Rapeseed puts glucosinate into the soil, and that tends to suppress nematodes, he said.
Jeong is also working with a combination of rapeseed and hairy vetch to see how much carbon and nitrogen is added to the soil by the plants.
He said an evaluation will be done to see if hairy vetch and rapeseed increase crop yield. The project also examines whether the microbial community was affected by the two cover crops.
Lisa Fultz, an LSU AgCenter soil microbiologist, is wrapping up a four-year study on using legume cover crops to reduce the amount of nitrogen needed for corn.
Corn yields increased 10 to 20 bushels an acre on fields planted with crimson clover, hairy vetch and winter peas compared to fallow fields, she said, and it’s likely the legume cover crops added nitrogen to the soil.
“It looks like we are making use of some of that nitrogen,” she said.
But soybeans grown where cover crops were planted did not show a similar yield increase, she said. Her study also showed that following some cover crops, nitrogen could be reduced by half to 80 units, and the same corn yields would be obtained as plots fertilized with 160 units.
Benefits, in addition to any yield increases, are being evaluated. For example, she said plots planted to cover crops were weed-free for planting. Cover crops also reduce erosion and add organic material.
She said the Louisiana Soybean and Grain Research and Promotion Board funding for the cover crop study helped leverage federal money for a statewide cover crop study for cotton, sugarcane, soybeans and corn at 16 locations throughout the state.
Brenda Tubana, LSU AgCenter agronomist, is studying planting dates and optimum fertilization rates for effects on cover crops’ biomass production and nutrient recovery.
She said the September and October plantings for hairy vetch, crimson clover and tillage radish had better plant stands and biomass production than the November planting of these cover crops. Applications of 15-15-15 fertilizer showed enhanced growth of the three cover crops.
Josh Copes, LSU AgCenter agronomist and weed scientist, is studying various mixes of cover crops in rotations of corn-soybeans, corn-cotton and cotton-soybeans in both minimum tillage and conventional tillage systems.
“This is looking at what cover crops are doing not only to yield but also to the soil,” Copes said.
Cover crops include hairy vetch, cereal rye and black oats, and mixtures of cereal rye plus hairy vetch and black oats plus hairy vetch. Cover crop mixtures are in a ratio of 70-30 or 30-70 ratio of cereal rye to legume cover, respectively.
Copes is also studying how cover crop termination dates affect crop yield, soil properties and nematode populations. This study is conducted in both minimum tillage and conventional tillage systems in rotations of corn-soybeans; corn-cotton; and cotton-soybeans.
Cover crops in all rotations are a mix of black oats and hairy vetch in ratios of 70-30 or 30-70 of black oats to hairy vetch, respectively, depending on what crop is being grown. Termination of dates of cover crops are six, four, and two weeks before planting corn (March 15), cotton (May 1) and soybeans (April 15).
Results from planting in later-terminated cover crops is showing soybeans in the early reproductive stages have spindly growth, he said, because of plants trying to grow above the crop canopy.
Syam Dodla, LSU AgCenter agronomist, said his research has shown that soil compaction associated with no-till systems is lessened by adoption of winter cover crops. Additionally, weed management is simpler under cover crops compared to fallow ground that minimizes weed issues during main crop, and incorporating legume cover crops also helps fix nitrogen in the soil.
A long-term fertilization study for the rotation of corn and soybeans is showing that corn removes more phosphorus than soybeans, but less potassium.
Results from 2017 showed corn removed 25 pounds of phosphorus per acre, compared to 15 pounds for soybeans. In the same year, corn removed 32 pounds per acre of potassium, compared to 40 pounds for soybeans.