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Farmers find that the layer of cover crops protects and enriches the soil

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Mahdi Al-Kaisi

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Posted: Sunday, October 7, 2012 12:00 am

Do you ever drive down a highway, glance at a farm field and wonder why the grass is growing in corn or soybean stubble?

For centuries, farmers have been using cover crops to prevent soil erosion, improve nutrient cycling and sustain their soils. This year's conditions have renewed many growers' interest in cover crops to help mitigate the effects of the drought.

Jack Smith, who farms near Bankston, Iowa, isn't new to cover crops. This year, he used aerial seeding with his rye crop planted in his corn fields on Aug. 29. His intention was to do it even earlier, but he struggled to get an airplane.

Last year, Smith planted the cover crop after his corn was harvested. Smith's primary motive was to grow some extra feed for his feeder cow herd.

"Obviously there are going to be some benefits to the soil by increasing organic manner as well as from the perspective of preventing soil erosion," he said. "You're also tying up nitrogen that would normally leach into the groundwater over the winter."

a growing trend

Besides the rye, Smith has planted oats and oilseed radishes -- that the cattle love to eat.

"We aren't reinventing the wheel," Smith said of cover crops. "The popularity is increasing. And the beauty of aerial planting is there is no work involved for the producer. All you do is pay the bill, about $40 an acre and that includes plane."

Jeff Pape, a Dubuque County commodities crop producer, agrees with Smith. He had 50 acres of oats flown into his beans as cover crop this year.

Courtney Myers, a Natural Resources Conservation Service soil conservationist in Epworth, Iowa, worked with several producers who aerial applied a combination of tillage radishes, turnips and rye. She said several farmers drilled in oats after they chopped corn for silage. Myers said cereal rye always is a popular cover crop, and for the first time triticale (a cereal rye and winter wheat cross) is being used regularly. Myers said the Epworth office is being "overwhelmed" with calls about cover crops, but she called it a "great" thing.

why plant cover crops?

Mahdi Al-Kaisi, a professor of soil management with the Iowa State University agronomy department, encourages producers to consider planting cover crops.

"It's a win-win situation, especially in the area around Dubuque with the rolling terrain and high slopes," he said. "It's very protective of the soil and helps increase productivity."

He said there are numerous NRCS programs to help producers find the what, where and how to plant.

Jason Johnson, an NRCS public affairs specialist in Des Moines, said cover crops have been available for a long time. Johnson said effort and research by Iowa State University has improved the variety and diversity of cover crops.

"Different types of cover crops do different things for farmers," Johnson said. "But they are becoming more popular and widespread."

Cover crops protect the soil. Al-Kaisi said that after the harvest, the soil is exposed to weather conditions for almost seven months with no active plant activity. It's vulnerable to erosion.

"It generally has a very positive impact on soil quality," he said. "It improves the soil structure stability and adds a lot of organic matter to the soil as well."

Planning is critical for producers. Al-Kaisi said they need to take advantage of a short window, generally from early September to the end of October, to plant the crop. This year was exceptional, with many producers harvesting their corn crop earlier than normal because of the drought. It's important to plant before the first frost.

"You want to establish a good stand," he said. "By doing that, you minimize cover crop damage due to the freeze and cold weather. In cold weather, the crops struggle to germinate."

Winter cover crops are planted in early fall and allowed to grow over the winter until early spring, when their growth is terminated by plowing or herbicide treatment.

According to Diana Jenkins, of the National Institute of Food and Agriculture, cover crops offer many benefits: they conserve water, improve the quality of soil, suppress weeds and control insect pests and erosion.

Cover crops also can provide an excellent source of animal feed during periods when drought has reduced forage.

National soils expert Ray Archuleta tells farmers to add living roots to the soil during more months of the year to increase organic matter and improve soil health. Along with eliminating tillage activities, Archuleta touted legume cover crops as natural fertilizers and grasses as scavengers of nutrients often lost after harvest or during winter.

"Diversity above ground improves diversity below ground, which helps create healthy productive soils," Archuleta said. "Cover crops should be an integral part of a cropping system. They help improve soil health by developing an ecosystem that sustains and nourishes plants, soil microbes and beneficial insects."

He said that cover crops also protect soil against erosive heavy rains and strong winds. They can provide livestock producers with additional grazing or haying opportunities and winter food and cover for birds and other wildlife.

nitrogen's effect

Nitrogen is the single most important input a farmer can control to increase crop yields on non-irrigated fields.

Cover crops also scavenge residual nitrogen and recycle it through their plant biomass, notes Barb Stewart, Iowa NRCS state agronomist. Excess nitrogen causes serious air and water pollution problems and even might threaten the health of the soil.

She adds that, as cover crops decompose next year, some of the nitrogen taken up by the cover crops will be released for use by the next cash crop, and some will go toward building soil organic matter.

"Fall-planted cover crops would be a good investment this year, to benefit both their own farms and regional water quality," Stewart said.

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