MAKING COVER CROPS WORK IN NORTHERN REGIONS By Sarah Hill, Associate Editor, No-Till Farmer
South Dakota NRCS agronomist Jason Miller shares tips on customizing a cover crop system to less-than-ideal growing conditions.
C
over crops have been slower to catch on in northern regions because there are more obstacles than in warmer climates. A shorter growing season, fewer days of sunlight, and in recent years, more moisture, have all proven challenging for northern growers who may have considered cover crops. At the 2020 National No-Till Conference, Jason Miller, an NRCS agronomist based in South Dakota, shared insights on how cover crops can be used to meet growers’ objectives, even in northern climates. Miller has been with NRCS for 30 years. He’s been working with the Dakota Lakes Research Farm near Pierre, S.D., since 1997. During his career, Miller has learned that cover crops are just one component of a soil health system, in addition to crop rotation, no-till, nutrient management and integrated pest management. According to Miller, increasing soil health and/or quality should be the main focus of any cropland system. “Restoring soil resilience is a must,” he says. “Soil resilience, increasing organic matter, improving soil biology, improving water filtration and decreasing soil compaction ultimately add more dollars in your pocket and improve crop production.” SELECTING COVER CROP SPECIES Miller suggests that growers consider multiple objectives when selecting cover crop species. “What will the following year’s cash crop be? Will it be corn, soybeans, wheat? What herbicides have been applied to this year’s cash crops and what implications do those have on what you want the cover crop to do?” he asks. “If you’re looking to produce a lot of biomass quickly, raising brassicas may be the way to go,” says Miller. “Within 30-45 days, as long as moisture and nutrients are adequate, there is a lot of growth.” “They’re excellent at nutrient scavenging,” Miller adds. “In South Dakota, we have to limit the brassicas in the mixture, especially as you go west, due to the brassicas breaking down the previous crop residue too quickly the following summer.” Previous crop residue is extremely important to the performance of the current cash crop in reducing soil water evaporation.
16
“Farmers in the eastern part of the state don’t like residue because things are wet, so they want to plant brassicas. It really doesn’t start breaking down that residue in time to help you with planting. You start seeing that residue disappear from July to September.” “Peas are an excellent cover crop,” Miller says, “but growers should be cautious not Jason Miller, NRCS Agronomist to mix species of peas that are used as a cover crop if they are also growing pulse crops for a cash crop, due to the risk of carrying over root diseases.” Miller says what you want to get out of your cover crop should drive what you put into it. “That means if you’re planning to graze it, it may make sense to add some fertilizer to get more biomass if nitrate N soil test values are low.” “If you’re just growing covers for soil health purposes, then you don’t need fertilizer. If you take off a high-yielding wheat crop with questionable protein, then you probably have a deficiency, so you’re not going to get a lot of cover crop growth out of that.” Miller says he always adds oats and flax to a cover crop cocktail because they’re friendly to soil biology and encourage mycorrhizae that help extract water from the soil profile. For fields with shallow compaction, Miller recommends using annual ryegrass, oats and other small grains. “We have cover crop species that will address surface and sub-surface compaction,” he says. “I like those with fibrous root systems, like small grains, for surface compaction. When you get into deeper compaction, that’s where the brassicas like radish and rape tend to help alleviate the sub-surface compaction.” “Providing weed control with cover crops is kind of a no-brainer,” Miller says. “Anytime we can get something green growing out there that’s going to provide some competition for weeds, it’s a positive, whether it’s germinating or growing.”
Summer Issue 2021
SDSL
