ISU to study land rolling soybeans
By Jean Caspers-Simmet
Date Modified: 08/02/2012 2:08 PM
NASHUA, Iowa —Iowa State University Extension soybean agronomist Andy Lenssen outlined a major study he is heading up on land rolling soybeans at the recent summer field day at the Northeast Research Farm at Nashua.
Lenssen said that while few northeast Iowa farmers land roll soybeans, it is estimated that 70 percent to 80 percent of the soybeans in northwest Iowa are rolled.
The research study, funded by the Iowa Soybean Association, includes three studies on small plots at ISU's Ames and Sutherland research farms. The fourth study is on 11 northern Iowa farms which are part of ISU's Farmer Assisted Research and Management program.
All are comparing land rolled soybeans with soybeans that aren't rolled.
"In North Dakota and eastern Montana where I was at before I came to Ames, all the peas, all the lentils and most of the hay ground is rolled," Lenssen said. "Rolling pushes rocks back to the soil surface and makes harvest easier. You're not breaking sections or guards or picking up rocks. By pushing down corn root balls, you have cleaner beans."
Lenssen, who worked for the University of Montana and then for USDA's Agricultural Research Service in Montana, conducted several research trials with land rollers.
He found that rolling functions like a packer wheel for small-seeded weeds and improved soil to seed contact and germination. Rolling doubled and in some cases tripled recruitment of small-seeded weeds.
The ISU research farm studies will look at conventional and no-till, planting dates, planting rates, genetics and weeds on rolled and non-rolled soybeans. The on-farm trials consist of replicated plots with 30-inch to 45 inch-wide strips up to 1 mile long.
Lenssen said that rolling puts 3 to 5 pounds of weight per square foot on the soil.
"It you're pushing rocks into the soil you're also pushing down on the soil," Lenssen said. "That's compaction."
A study at the Northern Research Farm at Kanawha that looked at the water infiltration rate of rolled soybeans found that land rolling cut water infiltration.
"Does that mean anything?" Lenssen said. "We need all the water we can get in the soils this year, and most years we want to store as much water as we can because in July and August there's less precipitation than what is needed."
ISU graduate student Allistair Lee will measure water infiltration rate, soil penetration resistance, soil bulk density and soil water at several depths on soybeans that have been rolled and soybeans that have not. Yields of rolled and nonrolled beans will also be compared.