Current soil health initiatives involve more intensive management and reflect more environmentally suitable systems than those in the 1990s, LSU AgCenter associate vice president Rogers Leonard told producers attending recent cover crop and soil health field days.
Two workshops set in the northeast region as part of a federal initiative to highlight soil health research efforts were sponsored by the LSU AgCenter, the Louisiana Master Farmer Program, the Natural Resources Conservation Service and the Louisiana Department of Agriculture and Forestry.
The first workshop was held Feb. 7 at the Scott Research and Education Center in Winnsboro, followed by a Feb. 13 event at the Northeast Research Station in St. Joseph.
Steve Nipper, NRCS water quality specialist, said cover crop selection depends on many variables, the most important being the cash crop that follows termination.
“Treat the cover crop as you would the cash crop for spring planting,” Nipper said.
Growers should have a clear goal in mind and consider termination requirements when making cover crop selections, especially when selecting cover crop mixes, he said.
“Always start with a small grain if using a mix and know what will be needed to take it out,” Nipper said.
AgCenter agronomist Josh Copes said most farmers plant cover crops by broadcasting seed, but direct drill planting provides a more uniform stand.
“One drawback to grower adoption of winter cover crops can be the cost of establishment,” Copes said, adding that planting methods that don’t require additional passes across the field are being explored.
Cereal rye and tillage radishes have been most effective in reducing weed density, Copes said, but the radishes can be difficult to terminate if allowed to flower.
AgCenter soil microbiologist Lisa Fultz said cover crops show potential for recuperating nitrogen in the soil so it can be available for cash crops.
Increasing biomass and plant residue at the soil surface and minimizing soil disturbance increases the numbers and types of soil organisms that break down and incorporate organic matter into the soil, Fultz said.
Grass and legume species, such as cereal rye and winter peas, yield greater increases in available nitrogen following corn compared to tillage radishes and a cereal rye-radish mix, she said.
In monoculture cover crop trials at several research stations, soybean yields have shown significant increases compared to unsprayed fallow plots, she said.
Fultz said there are opportunities for producers looking to participate in on-farm cover crop demonstrations through a NRCS Conservation Innovation grant.
AgCenter plant pathologist Charles Overstreet told producers that cover crops may present potential problems with nematode control, particularly reniform and Southern root knot species.
Overstreet said growers should know what nematode populations are in the field, and select resistant varieties to reduce populations, or at the very least limit their growth.
All grasses and crucifers are poor hosts for reniform nematodes, Overstreet said, but only Cahaba vetch has been shown to be effective in reducing populations of Southern root knot nematode.
“Although some cover crops may be poor hosts, producers may see little population control benefit since nematodes are not active in cooler temperatures,” he said.
Overstreet recommended delayed planting of cover crops until soil temperatures fall below 65 degrees when nematodes are least active, and termination before soil temperatures warm up for best results.
For farmers intent on planting into green cover, AgCenter entomologist Sebe Brown said it is vital to have a robust insect protection package, whether a seed treatment or below-ground insecticide.
“Where we plant dirty into green material, we see a greater impact from insects,” Brown said.
“By keeping the ‘green bridge’ growing, insects are allowed to overwinter in the field and carry over into the cash crop.”
The AgCenter recommends terminating cover crops four to six weeks before planting the cash crop to break the green bridge, he said.
Brown said early-season insect pressure from thrips in cotton is 100 percent guaranteed, with or without cover crops.
In cotton, a base seed treatment containing two modes of action, such as imidacloprid and thiodicarb, is ideal. Poncho 1250 is the “Cadillac treatment” for corn, especially if planting green, he said.
“There are no rescue options for below ground pests. Once the damage is done, you can’t take it back,” Brown said.
AgCenter plant pathologist Trey Price said the biggest concern with minimum or no tillage cover crop systems is they may encourage plant seedling diseases.
Cover crop systems increase soil moisture, lower the temperature and create an environment favorable for seedling diseases, he said.
Price said cover crop seed placement may be an important consideration.
Drill planting cover crop seeds to the side of rows, leaving the row top bare, will make planting the cash crop easier and reduce seedling contact with cover crop debris, he said.
Information is limited on the impact of cover crops on seedling disease pathogens, Price said, adding that most base fungicide seed treatments should be sufficient.