ROCHESTER, Minn. – The effect of cover crops on nitrogen and nitrate levels was the highlight of a field day presented by University of Minnesota-Extension in Winona County. As an example of good practices, Joe Lawler demonstrated his high-boy seeder. Bob Christie with son-in-law D.J. Muller showed their corn that was planted into a rye cover crop.
Lawler is a sixth-generation farmer. He said he wanted to go in a different direction from his predecessors. With his dad’s blessing he began exploring no-till, with the goal of transitioning to organic. He began to use cover crops, wanting to seed earlier into full-grown corn. He said he looked at a commercial machine, but found it too expensive for his budget. When he heard that Pioneer was selling some of their detasseling machines, he made a trip to Canada to buy one.
“This is Johnny Cash,” said Lawler, referring to the famous song, “One Piece at a Time” in which Cash sings of putting together a Cadillac a piece at a time.
Lawler spent more than 400 hours modifying his machine. He added 5 feet to the wheel base for the added air seeder and strengthened the frame. He mounted a Honda engine to run a blower for the seeder among other things. The boom was a challenge. It took many tries before he found the right combination so that it swings up, and tilts up and down. Seed diffusers were mounted every 30 inches to spread seed evenly. It can interseed in corn from 4 to 13 feet in height; it covers 60 feet in width.
The machine is limited by the size of the hopper; it can hold 2,500 pounds. Lawler uses it in mid-September to broadcast cereal rye and brassicas. Future plans are to add row dividers on the wheels for use in bean fields.
A few miles down the road from the Lawler farm, Christie and Muller are using cover crops. This the first year they were used on the whole farm.
“It’s been a learning experience,” Christie said. “We’re real excited with what we’ve seen so far. My focus for 50 years has been preserving water on my light ground. When I run out of moisture my crops suffer.”
Muller dabbled with using cover crops on the farm, but time restraints created pitfalls.
“Each year we had more bushels, but less money,” he said. “I had to do something different.”
After taking time to do some research, he started again.
Christie and Muller planted rye this past fall and had good spring growth. Corn was planted the fourth week of May.
“Planting green is a no-brainer to me,” Christie said. “It’s scary to plant into a green cover crop the first time.”
The rye is 2 to 7 inches when the corn is planted, and about a foot tall when terminated.
Muller said his gauge wheels on the corn planter were clean so he has more consistent depth. He likes that he can recycle nutrients, and he had good control over broadleaves this year. He considers his biggest success using no-till are cost savings by using less diesel fuel, along with less wear and tear on the tractors. By concentrating on return on investment instead of bushels per acre he’s hopeful to be able to pass a profitable farm to his son. Future plans are to try more diverse cover crops.
Martin Larsen from the Olmsted County Soil and Water Conservation District office was on hand to explain and illustrate why cover crops are needed. He works on various field trials for the district as well as on his own farm near Byron, Minnesota. He said researchers are becoming good at predicting nitrate levels leaching out of the soil profile and into the groundwater, even though there are many factors that affect nitrogen use. He said he thinks the main key is not disturbing the soil any more than necessary. The perfect crops are those with fibrous root systems.
Where tillage is done, water stops at tillage depth and then pools on top because the soil needs to re-set itself after it’s disturbed. The sweep on a field cultivator causes the dirt to smear, creating a stopping point for water. In contrast where there are worm holes and root channels, the water is allowed to flow into the soil. Increased infiltration means less water flushing down the fields or ponding on top of the soil.
“It’s not all roots,” Martin said. “Organic matter, soil health and bacteria hold soil together.”
Rainfall, management style, soil types, nitrogen sources and application all make a difference in nitrate levels.