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Top Tips For Corn On Corn
Mindful of an emerging trend, an agricultural engineer offers guidelines to thoughtful decision-making for no-tillers thinking about leaping into monoculture corn.
By Ron Ross
Before Paul Jasa will even discuss no-till continuous corn, he issues a strong warning about monoculture farming. The highly respected University of Nebraska extension agricultural engineer has worked for more than 30 years "preaching" a systems approach to no-till, including crop rotation.
"Many of the problems that we've worked on for years — such as nitrate leaching and atrazine in runoff, corn rootworm management, nitrogen response for corn and generally lower yields in mono-crop systems — are greatly reduced with properly managed crop rotations," Jasa says. "A systems approach to continuous no-till, including crop rotation, has also proven to resolve many other potential production headaches, such as crusting and a lack of infiltration that is often typical of tilled soils, soil compaction, erosion and runoff, and poor soil health," he adds.
"But having said that, I realize there has been considerable interest in no-tilling corn on corn. Whether that interest stems from a growing ethanol demand for more corn, soybean rust scares or other reasons, it's happening, and educators need to address it," Jasa continues. In response to the trend, he drafted a list of considerations and recommendations to help growers make no-till corn on corn more successful or, from his perspective, "less risky."
Jasa's points to consider fall into four areas: general, harvest and residue management, nutrient management and planting of continuous corn.
1. No-Till Monoculture Problems. Conventional tillage farmers in Nebraska who tried monocultures, including corn on corn under irrigation, lost the crop rotation benefits of pest control, soil tilth, soil biological activity, workload spreading and yield. When no-till and high residue were added to the mix, problems were often magnified to "explosive" levels.
2. Unstable Markets. You might be attracted to premium prices offered by a new ethanol plant, for example, but after the plant is up and running, and plenty of corn is available, prices will likely moderate. Is the potential short-term income worth the higher production expenses, increased risks and lower yields that are inherent with monoculture?
3. Hybrid Rotation. If you grow a racehorse hybrid this year for maximum yield, be sure to select hybrids for continuous corn next season that are rated resistant or tolerant to diseases that overwinter in corn residue, such as gray leaf spot. And don't just change hybrid numbers within the same parent lines; they'll show the same susceptibility to the disease.
4. Pest Management. Use a soil-applied rootworm insecticide or consider insect protection traits and/or treated seed. The potential for rootworms and secondary insects to overwinter is much higher in corn on corn.
5. Preplant Weed Control. Insects are drawn to green vegetation to lay eggs. No-tilling corn into corn stubble where weeds are actively growing sets you up for potentially serious yield losses. Preplant herbicides can remove potential insect habitat and conserve soil moisture.
6. Herbicide Resistance. It's easy to over-apply glyphosate in a continuous corn system, because glyphosate might be used for burndown as well as one or two in-season applications on Roundup Ready corn hybrids. This sets the stage for glyphosate-resistant weeds 4 or 5 years down the road. Advice: Use multiple modes of action and keep glyphosate out of the field at least every other year.
7. Strip-Till Profits? On flat, square, large fields, strip-tilling can be an easy solution to accelerate drying and warming of soils. But multiple research results conclude that strip-tilling probably won't pencil out in well-drained soils. Unfortunately, many studies have compared a perfect strip-till system with an imperfectly managed no-till system, especially regarding fertilizer placement.
Ask yourself if an investment in strip-till equipment for continuous corn is justified if you can get equal returns with a continuous no-till, diverse rotation strategy without the expense of added machinery.
8. Ridge-Till Possibilities? While ridge-tilled acres have sharply declined, this simple system for conserving moisture while providing a warm planting environment works well with continuous corn. Maybe corn on corn is a good reason to bring the row-crop cultivator out of the shed.
HARVEST AND RESIDUE MANAGEMENT
9. Snapping Rolls. Use of the corn head is the first chance to process this year's corn residue and make no-tilling corn back into it easier – and less risky – next spring. Knife-to-knife or tapered snapping rolls give more aggressive lacerating action to the stalk, accelerating microbial action and decomposition. Some new corn heads, such as the Drago system, have 50 percent longer knife rollers and do an excellent job of drawing tall stalks straight down to the ground.
10. Stalk Height. Position the corn head to leave 8 to 10 inches of stalk anchored and upright with the upper stalk chopped and spread out on the ground. This allows good air movement down to the soil surface, encouraging faster residue breakdown. Stalks left 2 or 3 feet high will not likely break down over winter and can cause costly planting problems.
11. Combine Wheel Spacing. Space combine wheels between the rows to leave the residue standing. If you run over the residue, you will be planting into a compacted wheel track, creating two different seeding conditions. Also, a more even winter snow catch across the field (more likely if stalks are of equal height) will result in uniform soil moisture and temperature for planting.
12. Expanded Grazing. Cattle provide a profitable means for reducing residue levels and cleaning up volunteer corn. Some cash grain operators growing continuous no-till corn earn extra income by renting harvested corn fields for fall and winter stalk grazing.
13. Cover Crops. Planting a cover crop, such as cereal rye, immediately after combining provides an even better grazing opportunity and improves soil quality. Beware: planting wheat as a cover crop into corn stalks is risky, because corn and wheat host similar diseases (such as fusarium).
Cover crops also help dry out poorly drained soils and aid warming in the spring. A non-grass cover crop, such as brassicas, will affect carbon/nitrogen ratios, resulting in more soil biological activity and faster residue breakdown. In higher rainfall areas, a cover crop is a much better alternative for excess water than running it down a drain tile or deep into the soil.
14. Leave Residue Attached. Fluffing the top layer of soil with a rotary harrow or similar tool may seem to be a good way to speed up drying and allow earlier planting. But often these machines detach residue, knock it over and create a heavy residue mat that interferes with planting. Consider them "transitional" tools and use them only until you have developed good soil structure with continuous no-till.
15. Nitrogen Placement. Applying nitrogen below the soil surface is preferred regardless of the rotation. Strip-tilling allows placement below the surface of liquid, dry or anhydrous ammonia fertilizer, while a number of minimum soil disturbance placement systems are available for liquid and anhydrous in no-till. There are fewer options for minimum soil disturbance with dry fertilizer applications.
16. Nitrogen Penalty. The "penalty" for corn on corn adds up to an extra 40 to 50 pounds of needed nitrogen per acre to make up for the loss of a legume. The application of the penalty pounds corrects the carbon/nitrogen ratio and causes faster residue breakdown. A legume cover crop could reduce this penalty.
17. Nutrient Timing. Avoid fall nitrogen applications to prevent leaching on sandy soils or running nitrogen down drain tiles in higher-rainfall, heavier-soil areas. Split nitrogen applications — a healthy starter fertilizer combined with sidedress, or double sidedressing — is much more efficient.
18. In-Furrow Pop-Up. A 10-34-0 blend is recommended in the furrow for no-till corn. Potassium and sulfur are not recommended for in-furrow application because of potential seed damage. With corn on corn in particular, heavy residue often keeps the soil surface wetter and colder, so corn roots are slower growing. You might have plenty of nutrients between the rows, but you need them closer to the furrow to be available to challenged young seedlings.
19. Extra Starter Nitrogen. A number of research studies suggest that at least 30 pounds of nitrate nitrogen per acre should be available by V5 leaf development in continuous corn to avoid crop stress. Either dribble a band of nitrogen on the surface behind the planter, or apply nitrogen with a starter attachment set 2 to 4 inches to the side of the seed furrow.
20. Sharp openers. Double-disc openers, if sharp and working properly, cut through residue better than coulters. The no-till planter openers should be working together as a single cutting edge.
21. Off-Row Seeding. Avoid planting in the heart of the wheel track. Planting 4 inches to the side of the old row works well with corn on corn. This also reduces tire wear compared to planting between the old rows.
22. Planting Speed. Keep speeds at 4 to 5 miles per hour to reduce planter unit bounce and deliver seeds uniformly. Be wary of ads that say a given planter can "meter seed" at 7 to 8 mph. That doesn't mean it will provide good seed placement at higher speeds.
23. Down Pressure. The heavier residue of continuous no-till corn, especially in hard, dry soil, requires down pressure springs and extra weight (as necessary) on the no-till planter to cut through and penetrate the soil to achieve desired seeding depth.
24. Uniform Depth. Keeton Seed Firmers or Schaffert Rebounders are particularly recommended in heavy-residue continuous corn conditions to get all seeds to the bottom of the seed trench for more uniform emergence. These units also provide convenient in-furrow fertilizer application features.
25. Residue Movers. Consider residue movers on the no-till planter to warm poorly drained soils and to "even up" and create a uniform residue layer. (First time no-tillers often don't have residue everywhere in the field).
However, if the residue cover is already uniform, such as in long-term no-till, residue movers can do more harm than good. In these cases, the movers break residue loose from the soil without cutting it, and the residue then blows back over the row. (This might be less of a problem in higher-rainfall areas). Emerging corn leafs out under the residue and is starved for sunlight.
26. Spoked Closing Wheels. They serve two purposes: drying the soil and closing the seed trench. However, depending on your drainage situation, closing wheels might dry out the soil too much. In some cases, growers get better results using one spoked wheel and one regular closing wheel. Also, some closing wheel brands have less aggressive spokes than others.
27. Changing Coulters. Traditional coulters are on their way out. Best advice: Don't use coulters that pull up wet sticky soils, make air pockets below the seed or over-dry the seed zone. Twin-coulter systems provide much better seed-to-soil contact, and by providing tillage on either side of the row they help dry out the soil without affecting seed zone moisture.
28. A "Nu-Till"-Type System. Continuous no-till corn growers might want to consider a "Nu-Till"-type system. Special planter attachments including row cleaners, fertilizer attachments, seed firmers, spader wheels and twisted chains allow tilling, fertilization and planting in one field pass (see www.maximumfarming.com).