What do winter peas, red clover, rapeseed, winter rye, sorghum-sudan, tillage radish, hairy vetch, ryegrass, and sunflowers have in common?
All are or have been cover crops grown within the past seven years by an Oconomowoc (Waukesha County) family which specializes in growing corn, soybeans, and winter wheat as cash crops on some 4,000 acres in parts of four south central Wisconsin counties.
Speaking to that point at the annual Fond du Lac County agronomy day was family member Nick Miller, who said his father's goal is to have per acre yields of 300 bushels for corn that's grown in 20-inch rows and 100 bushels for soybeans. He reported that the farm's approximately 600 acres of winter wheat, grown mostly on lighter soils, averaged 128 bushels per acre this year.
Miller said the family follows two basic rules: “plant something” and “never plant a cash crop as a cover crop.” With the drop in the market price for corn from over $6 per bushel three years today to about one-half of that today, he said another guideline is to limit the per acre seed cost for cover crops to $15 compared to the $25 to $30 that was affordable with the much higher corn price.
The current low budget cover crop seed mix includes per acre rates of 25 pounds of peas, 1.5 pounds of tillage radish, and 1 pound of rapeseed along with some sunflowers and sorghum-sudan, Miller indicated. Following soybeans, up to 75 to 80 pounds of ryesgrass have been seeded per acre with a spinner spreader, he noted.
When winter peas are included in the cover crop mix, the timing of the planting is crucial, Miller emphasized. He listed August 1 as the ideal date but reported that, for a variety of reasons, the planting was delayed until August 15 this year and the development of the peas is lagging by about three weeks as a result.
With the winter wheat, frost seeding red clover in the spring - during the early a.m. hours in March when the soil surface is frozen - is an option for establishing a nitrogen fixing crop that comes into prominence once the wheat is harvested, Miller observed.
But that's not done when the intent is to bale and harvest the wheat straw - as was done this year to the tune of 3,500 large rectangular bales, Miller reported.
Winter rye is also grown on 700 to 800 acres per year, Miller continued. As necessary in the spring, herbicide products are applied to terminate the growth of any cover crop species that survived the winter.
Soil variation challenges
The soils on the 4,000 acres are quite variable, Miller pointed out. For corn, the typical potential yields range from 140 to 260 bushels per acre, he said.
With no recent history of consistent manure applications, there's a shortage of residual phosphorus and potassium, Miller observed. The farm obtains manure from a herd of 30 beef cows and also buys chicken manure that's trucked about 30 miles and is applied at 1 to 2 tons per acre.
The management protocol also involves efforts to achieve a desirable carbon to magnesium ratio, Miller stated. An enduring challenge is the shortage of moisture on light and gravelly soils – a problem for which cover crop residuals are providing a boost in water holding capacity, he suggested.