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Cover Crops Build Soil

Growing a full-season cover for grazing increases soil organic matter.

Cow-calf producer and no-till farmer Lance Gartner, Glen Ullin, North Dakota, grows full-season cover crops to build soil health and to provide early-winter grazing for cows.

Soil organic matter has increased as a result of the multispecies cover crops and the fertility contributed by cattle manure and urine. “Before I started growing cover crops seven years ago, soil tests showed my no-till soils had 2.3% to 2.9% organic matter,” says Gartner. “In recent years, my soils have tested 3.7% to 4.25% organic matter.”

The building of soil organic matter results in a reduced need for applying nitrogen (N) to wheat and corn. Gartner has reduced commercial N use for these crops by 60%, and sometimes he eliminates fertilizer applications altogether.

The yardstick guiding Gartner’s N-application rate is his estimate of N mineralizing from the organic matter. “The unavailable nitrogen doesn’t show up on soil tests, and what mineralizes is not immediately available to plants,” he says. “It becomes available to the crop slowly throughout the growing season.

“I allocate about 1,000 pounds per acre of unavailable N for each percent of organic matter,” he says. “I then figure 1% of this 1,000 pounds of unavailable N will mineralize. This yields 10 pounds of available N. When multiplied times 4% of organic matter, the result is a nitrogen credit of 40 pounds of available N per acre.”

He subtracts this credit from the recommended fertilization rate indicated by soil test results. “What I end up applying is typically 40% of actual recommendations,” he says.

With N applied according to this formula, Gartner’s corn has yielded up to 100 bushels to the acre. He has also produced 60-bushel and 75-bushel corn yields without applying any fertilizer.

less focus on yield

Corn in his area, on average, yields 80 to 90 bushels per acre and sometimes as much as 150 bushels. Gartner values his more moderate yields for their profitability within his production system.

“I focus on net profit, which is more important to me than yield,” he says. “Risk management is important to me, too. If I have drought or hail, I don’t have huge fertilizer bills to pay for with no crop income.”

In Gartner’s corn-wheat rotation, he typically grows a full-season cover crop preceding corn. Thus, the soil health benefits are spread over a two-year period of producing cash crops.

He no-till plants the cover crop by mid-June into the previous year’s stubble.

Species included in the cover typically include turnips, radishes, and hairy vetch, an annual or biennial legume that fixes nitrogen in the soil.

“Hairy vetch is a creeper in its growth habits and will vine upward around other plants,” says Gartner. “It has up to 20% protein, and the temperature can drop to 10°F. before it winterkills or goes dormant. When I turn cattle into the cover crop in December, the cattle love the hairy vetch. It has a persistent ability to self-seed, so without grazing, it can be hard to get out of fields.”

Other species in the cover crop mix vary with the year but may include flax, peas, oats, millet, corn, and sorghum-Sudan grass, crimson clover, sweet clover, and sunflowers.

“Last year, I also had brown midrib sorghum-Sudan grass and grazing corn,” says Gartner. “Those species reportedly hold their protein content into late fall and early winter.”

To seed the cover crop, Gartner uses a John Deere 750 no-till drill. “I usually plant the cover crop 1¼ inches deep or ¾ inch deep if the mix includes a lot of fine seeds,” he says. “I don’t put any fertilizer down with the cover crop.”

In the spring of 2014, Gartner planted oats along with a cover crop mix. The intent was to harvest the oats for hay. Wet weather in August prevented baling of the swathed oats but encouraged robust regrowth of the cover crop between swaths. “I got beautiful late-season grazing,” he says.

Transitioning Marginal Land

Over time, Gartner has transitioned the farm’s marginal cropland into grass/alfalfa stands for both haying and grazing. Present crop acres number 425. Of these, about 100 to 120 will produce a cover crop each year.

The cover crop provides elasticity in Gartner’s grazing of 275 cows on 3,800 acres of grassland. “I usually start grazing the cover crop in early December, after bringing the cattle home from native-grass pastures,” he says.

The cover crop provides nutritious grazing for the cow-calf pairs until the calves are weaned in mid- to late December.

“This past winter, after weaning, the cows grazed the cover crop until early January,” says Gartner. “After that, I put the cows on stockpiled native range or bale-grazing spots during extremely cold weather.”

If conditions prevent grazing of the cover crop, he simply no-till drills the next year’s cash crop into the standing residue. A temporary change for 2015 in production is planned for the crop acres. He’ll plant these to forage corn and harvest the corn by grazing yearlings in September.

“I’m not taking cash crops out of my toolbox, but because of personal goals, low grain prices, and high input costs, I did decide to take a break from farming this year,” explains Gartner. “I will continue to grow a cover crop mix and focus on building soil health.”

Catering to Bees

By growing and monitoring a 5-acre pollinator strip in the summer of 2014, Lance Gartner learned the habits of his North Dakota ranch’s bee population.

“Pollination of plants is required for food production, and we hope to provide habitat for these pollinators – the domestic honeybees as well as the native bumblebees,” he says.

The two-year project, to be repeated in 2015, results from a Natural Resources Conservation Service (NRCS) Environmental Quality Incentives Program (EQIP).

Local NRCS staff provided the seed mix for the plants; EQIP shared the $27-per-acre seed cost.

Species in the mix included hairy vetch, common vetch, phacelia, buckwheat, canola, cowpea, flax, radishes, sunflowers, soybeans, and three types of clover. Gartner also added marigolds, pumpkins, and squash.

“The phacelia did very well; it just kept on blooming and blooming,” says Gartner. “The hairy vetch bloomed nearly right up to the end of the year.”

As part of the EQIP agreement, Gartner or another family member recorded bee activity in the patch at two-week intervals. In each of two 100-foot tracts, they counted bees and estimated stage of bloom of the plants. The evaluations each took about one and a half hours.

“The common vetch, buckwheat, and sunflowers drew bees fairly well, but the clover, marigold, squash, and pumpkin blooms seemed less attractive,” says Gartner. “Because these plants are low growing, the pollinators seemed obstructed by the surrounding taller plants. The bees loved the canola, phacelia, and the hairy vetch.”

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