|Choosing cover crops depends on crop rotation, goal for soil|
|Thursday, September 05, 2013 12:15 AM|
BY JAMES J. HOORMAN
As crops start to mature, farmers are thinking about what to plant next. Planting cover crops to protect the soil from erosion and to improve soil health is a great option. Farmers plant cover crops to harvest sunlight and to feed the soil microbes. Plant roots directly feed the soil by exuding carbon compounds that soil microbes may use for food. In return, the soil microbes recycle soil nutrients for the plant and together they improve soil aggregation and soil structure.
I often get asked, “What is the best cover crop to plant?” The answer depends upon the crop rotation and what you want to accomplish. After corn for grain, cereal rye or winter rye is usually the best option. Cereal rye germinates at 32 degrees Fahrenheit and may grow under the snow. For best results, drill cereal rye at least 1 inch deep or down to moisture. Cover crops can be flown on, applied with a highboy applicator between the rows (drop down nozzles), or broadcast with fertilizer or by themselves. With dry conditions, broadcasting cover crop seed is risky because the seed generally does not germinate until weather conditions improve.
Seeding rates can vary from 0.5 bushel to 2 bushel per acre. Farmers who harvest corn silage will often seed cereal rye at 2 bushel per acre, apply manure, and then harvest 3-5 tons of spring forage before planting corn or soybeans. Manure or extra nitrogen is critical for good forage growth and to prevent the corn from turning yellow (N deficiency) next spring. In 2013, one dairy farmer harvested 5 tons/A of good quality forage from cereal rye (worth at least $200/ ton) before planting corn for silage. He applied dairy manure in the fall and the spring (8,000 gallons/A) or roughly 120 pounds of N each time. His crude protein was 12.5 percent where no manure was applied and 21% with manure applied twice. Cereal rye will absorb of its total biomass almost 3-3.5-percent soil N and 0.2-percent soil P.
Oats seeded after corn silage at 2 bushel per acre is another option if forage is desired resulting in 1-3 tons (with adequate moisture) by mid-December. If the farmer does not want forage, 0.5 to 1 bu/A oats, cereal rye or barley makes a great cover crop going to soybeans. Without manure, farmers should avoid planting grass cover crops before corn due to high carbon to nitrogen ratios unless they are willing to apply a large amount of N fertilizer.
What cover crop should I use if I have soybeans going to corn?
If the soybeans come off early (September), oilseed radish, oats, crimson clover, or winter peas may be options. Farmers can either drill or broadcast oil seed radish (Daikon varieties) at 3-5#/A by themselves or drill radish 1-2#/A with crimson clover (7-8#/A) or with winter peas or Canadian field pea (Windham or winter hardy variety at 17-18#/A, 1 inch deep). The legumes may supply 75-100#/A N to the next crop with good stands and adequate growth in the spring.
Most of these cover crops do best if seeded early in September with more variable results towards the end of September and early October for Northwest Ohio. All cover crops need moisture and adequate sunlight to grow and they need a minimum of 60 to 90 days of growth. With diminishing sunlight and colder temperatures, a day in September may be like 3 days of growth in October and a week in November. Planting an early maturing soybean or corn variety which is harvested earlier can greatly increase the success of fall planted cover crops.
Other cover crops to consider are kale and rape/canola which can tolerate colder weather. Kale seeded at 10#/A can produce as much as 10 tons of biomass/A in deer plots. Kale can also be grazed by cattle with protein levels as high as 25%. Kale should be planted 0.5-0.75 inches deep and at 3-4#/A as a cover crop. Rape is a wild cousin of canola and more hardy. Rape can also be grazed (9-10#/A) or seeded as cover crop at 3-4#/A about .5 inches deep. Both Kale and Rape are small seeded, brassicas (same family as oil seed radish) and require adequate sulfur for good growth. Brassica plant species tend to fumigate the soil and suppress weeds but they also can stink when they decay.
Planting cover crops help farmers protect their soils but also improve soil quality.