Manage Covers Like Cash Crops

Due to the fact that cover crops interact with cash crops, they should be included in your agronomic planning as well as your soil health improvement plan.
No wonder Uncle Sam includes incentives to plant cover crops in popular conservation offerings such as the Conservation Security Program (CSP). Applied with forethought, cover crops improve soil health (by reducing crusting, improving infiltration and building organic matter); scavenge nutrients (by keeping them out of groundwater and releasing them for a cash crop); provide nitrogen; control erosion and suppress weeds.

But note that qualifier, "applied with forethought," says Farm Journal Field Agronomist Ken Ferrie. If you choose the wrong cover crop or don’t get a good stand, you might get no benefit at all.

Cover crops must be part of your crop production plan, as well as your soil health improvement plan, Ferrie continues. To benefit from the right cover crop in the right field next fall, the planning process starts now.

Deciding what you want to accomplish will help you decide what cover crop to plant.

"Some farmers want only to comply with USDA programs," Ferrie says. "In that case, make sure you understand all the rules, such as when the cover must be planted and how long you must let it grow. Rules may vary by program and by locality."

If this is your first attempt at cover cropping, you might want to choose one that’s easy to manage. In colder areas, oats and radishes winterkill, so there’s nothing to manage in the spring. (In warmer areas, of course, they have to be killed just like any other cover crop.) If you feel bolder, choose a cover to accom­plish specific objectives.

For example, you might select annual ryegrass or cereal rye to scavenge leftover nitrogen, control erosion, improve soil quality, suppress weeds and even provide some grazing for livestock. Legumes such as hairy vetch and various clovers can produce nitrogen for your next corn crop. To improve soil bulk density, which reduces crusting and improves water infiltration, consider tillage radishes or deep-rooted ryegrasses. Most cover crop species provide more than one benefit, Ferrie notes.

Extra information source. "An excellent source of information about the advantages of various cover crops, their potential disadvantages, their suitability to various localities and much more is the book, ‘Managing Cover Crops Profitably,’ " Ferrie says. You can download the book, published by USDA Sustainable Agriculture Research & Education, free of charge at (Scroll down the page to find the book.)

Once you decide on your goal, look for cover crops that fit your region, Ferrie says. For example, if you want to supply nitrogen to next spring’s corn crop, you might consider hairy vetch, red clover, berseem clover or crimson clover if you farm in the Corn Belt or Mid-South. If you farm in the Northern Plains, your options would include hairy vetch, sweet clover or medics. To suppress weeds, a Corn Belt farmer might use cereal rye, annual ryegrass, wheat, buckwheat or oats, while a Southern Plains grower might select cereal rye or barley.

Figure out how your cover crop will mesh with your rotation. "If you grow continuous corn in northern regions, it will be harder to plant a cover crop than if you rotate corn and soybeans because you’ll have less time to plant after corn harvest," Ferrie says. "If you have wheat in your rotation, cover crops become much easier because you have a long window, from July on, to plant the cover."

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Be prepared to equip your planter with row cleaners to deal with increased residue produced by cover crops. Depending on your next crop, you might apply phosphorus and nitrogen in starter fertilizer to deal with the carbon penalty.

If you raise livestock, grow wheat and inject manure after wheat harvest, a cover crop fits like a glove, Ferrie notes. The cover crop can take up some of the nutrients and carry them over to the following cash crop while also improving soil quality.

Cover crop success can be affected by your choice of cash crop hybrids and varieties. "The length of your planting window—from harvest to freezing—limits your choice of cover crops and is a major factor in successful establishment," Ferrie points out. "The window gets even shorter as you go farther north."

Stretch your planting window. "You can lengthen your planting window by growing shorter-season cash crop varieties—for example, moving from a 110-day to a 102-day corn hybrid or from a Maturity Group 3.1 to a Maturity Group 2.6 soybean. In recent years, the seed industry has developed shorter- season varieties that yield as well as later-maturing types," Ferrie says.

In northern areas, planting a cover crop in timely fashion might require high-clearance planting equipment or aerial application. "Both methods are more difficult than using a ground planter," Ferrie says. "In corn, you may be able to improve the odds by planting an upright-leaf hybrid; it will let in more sunlight to help establish the cover." Arrange for high-clearance equipment or aerial applicators well before cover crop planting time.

Understand the impact of your cover crop on the following cash crop. "Cover crops are an investment in soil quality, erosion control and the other benefits," Ferrie says. The investment is worth making, but you have to acknow­ledge the short-term impact and plan for it in your budgeting.

"For example, a continuous-corn grower in the northern Corn Belt might plant a cereal rye cover crop to lower his soil’s bulk density and improve water infiltration," Ferrie continues. "He chose cereal rye because it has a longer planting window—up to Thanksgiving. Over time, healthier soil from cover cropping should have a positive effect on his corn yield. But in the short term, the allelopathic effect of the rye will reduce the yield of the following corn crop."

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Once you decide which cover to plant, make arrangements to obtain high-quality seed. "With all the demand for cover crop seed, supplies of some species may be limited," Ferrie warns. "Buy certified seed to avoid bringing weed seed into your fields."

Consult with your herbicide supplier to make sure the herbicides applied to your cash crop in 2014 won’t persist into your cover crop planting window.

"Don’t forget to consider rescue treatments because those late applications will remain effective later into the fall," Ferrie says. "If you plan to use a custom applicator to kill your cover crop in the spring, let him know your plans so he can be available when you need him."

No surprises. Check with your dealers, Extension staff or online sources to determine whether your cover crop will create disease or insect risks for the following cash crop. "For example, field peas and most clovers and ryes are hosts to lesion nematodes. So if lesion nematodes are already present in your soil, planting those cover crops could increase the population."

Increased ground cover could also lead to rodent problems. "If you have 13-lined ground squirrels (also called striped gophers), keep them under control from the start by using bait traps," Ferrie says.

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Wrapping can become an issue when planting into some cover crops, such as hairy vetch. In this case, using a coulter on your planter can help.

Just like switching from conventional tillage to no-till, expect to plant later because your cover crop will keep soil cooler and wetter. Options include planting cover-cropped fields last or moving up to a larger planter.

Equip your planter to handle more residue. "Row cleaners will push residue out of the way," Ferrie says. "But if wrapping becomes a problem in hairy vetch, just use a coulter."

Rolling a cover crop ahead of planting is popular in some areas. If you expect to need a roller, plan ahead for where to obtain one.

Apply starter fertilizer. "Cover crops increase the carbon penalty in two ways," Ferrie says. "They produce more residue for soil microbes to decompose, and they keep soil cooler so the microbes are less active. As a result, microbe populations will increase rapidly when the soil warms up at planting time, and they may temporarily tie up the soil’s supply of phosphorus, sulfur and nitrogen.

"Apply some phosphorus, sulfur and nitrogen with the planter. Band some nitrogen close to the row rather than broadcasting it," Ferrie says.

No question—cover crop planning adds another line to your to-do list, but the results are worth the effort.  

Building on the Systems Approach, the Soil Health series will detail the chemical, physical and biological components of soil and how to give your crop a fighting chance.


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