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Living Mulch for Corn
Given Southern growing conditions, white clover makes a year-round living mulch for corn. Researchers at the University of Georgia find that white clover provides most of the nitrogen (N) needed by the corn and wards off the worst of the weeds. The self-perpetuating cropping system benefits both soil and net profitability.
“We chose a variety of white clover – Durana – for its drought tolerance and vigorous growth characteristics,” says University of Georgia soil scientist Nick Hill. “Like all white clovers, this variety regrows from above-ground stolons, which permits it to recover and regrow into open areas in a field.”
To make planting rows for the corn, the established legume is sprayed with an herbicide to kill the clover in 10-inch bands centered on 36-inch rows.
“By corn-planting time in late March or early April, the clover stands 13 to 15 inches tall and contains about 160 pounds per acre of N,” says Hill. “Through the decomposition of residue at the soil surface, the killing of the clover releases some of the starter N fertilizer needed by the corn. We add another 20 pounds per acre of N to help the corn get started.”
As the corn grows, it shades the clover.
“The clover responds by dropping its leaves, which decompose and provide additional N,” he says. “It’s like a time-release capsule of fertilizer. The decomposition rate of the clover follows the N requirement for the corn.”
The width of the corn rows (as well as the width of the banded herbicide treatment) is key to the balancing act the system needs in order to work.
“There is a balance between having the clover successfully reestablishing at the end of the growing season, its inherent ability to outcompete the developing corn crop, and being able to produce enough corn to make a profit,” says Hill.
“In wider rows, more light penetrates the corn to get to the clover later in the year, which enables the clover to persist a little longer,” he says. “In narrow rows, it doesn’t. Also, if we spray herbicide in a wider band over the clover to prepare the field to plant the corn, it causes excessive damage to the clover, and it won’t be able to reestablish after the corn harvest. If we spray too little, the clover will outcompete the corn.”
After harvesting the corn in early August, Hill grazes livestock on the crop aftermath to remove the stover. “The corn residue on the surface inhibits the clover from growing,” he says.
The livestock graze the clover along with the stover. Yet, after grazing stops in early to mid-October, the clover regrows from the stolons remaining at the surface.
By spring, clover regrowth has filled in the previous year’s planting bands. The clover stand persists for about three years before beginning to thin, permitting weeds to get started.
Corn yields in the living mulch system are 12% to 15% less than yields of corn grown by conventional tillage.
Yet, N inputs are significantly less. Also, herbicide applications are reduced by 66% to 75% of the herbicide applications in conventional-till corn, says Hill.
Benefits to soil health pile on top of net profits. “The living mulch system increases organic matter, fixes carbon in the soil, improves water infiltration, and virtually eliminates runoff carrying soil particles,” he says.
Involving farmers is the next step in the research project, he says.