In this new age of high-yield corn on corn (without their moldboard plow of yesteryear), southeast Minnesota brothers Nick and Bob Bunne boldly increased their corn acres in 2007. They went from 2,900 acres to almost 4,500 acres on their 6,000-acre farming operation. What they discovered was the typical average yield reduction of 10 to 15%, but they still averaged 180 to 185 bushels per acre. The Bunnes are confident the yield gap will close.
Leave the tundra and head toward central Indiana where longtime no-tiller and precision-farming pioneer Mike Shuter achieved near-equal corn yields on 1,100 corn-on-corn acres last year no matter the rotation—following corn or soybeans. But he and son Patrick didn't arrive at their 182-bushel average in only two years on their farm near Frankton. Mike figures it's been 20-plus years in the making.
While these two operations differ in approach and environment, the lessons learned offer value to a wide variety of corn-on-corn aficionados. The Bunnes must deal with a shorter season (including hybrid differences) because they're 200-plus miles farther north. They plant in 20-inch rows in a conservation tillage environment versus Shuter's 30-inch rows planted using strip till.
All the farmers have a similar driver behind their push to more corn—a good local corn market. The Bunnes have three ethanol plants within 30 miles and a feed mill 7 miles away. Shuter has two ethanol plants within 25 miles, plus a 100-car grain terminal just down the road.
SHRED RESIDUE. The Bunnes plan numerous changes for 2008 corn on corn. "First, we buried more residue last fall by chopping stalks and using a more aggressive disk ripper to speed soil warm-up and improve the seedbed," Nick says. In spring, they make a field cultivator pass right before planting.
"Regarding fertilizer, we may try more nitrogen, as we only added 20 pounds for corn on corn [140 pounds] versus corn following soybeans [120 pounds]," Nick says. "Plus we used 10 gallons of 7-21-7 starter for corn on corn versus 7 gallons when following beans. Our challenge is that we can't sidedress any nitrogen because of our 20-inch rows."
The Bunnes did have some fields without much yield drag, "but it varied depending on hybrids, tillage, planting timing and soil texture," says Nick.
"Some lighter soils that we worked up early provided equal yields to corn after soybeans. We have to push the planting window earlier because we just don't get much time for our soil to warm up," he adds.
FAST START NEEDED. "Getting the crop off to an early, uniform start is critical because delayed plants act like weeds when they don't produce an ear—and perhaps that's why our ears didn't fill out the tips," continues Nick. A good seedbed is a must, with trash whippers on the planter to clear a black soil path. And hybrid selection is crucial to withstand various stress challenges from cool planting temperatures, diseases and insects, he adds.
The Bunnes saw improved plant health and stalk strength on the fields where they applied Headline fungicide at tasseling. "But I haven't closely examined the yield maps yet to determine if we got a yield boost," explains Nick. "Some fields without the fungicide had more lodging due to increased stalk rot. But 20-inch corn does help keep plants upright," he says. Insects were not a problem, as they used some combination of Poncho seed treatment or Bt-RW corn or Regent soil insecticide on all acres.
[PAGEBREAK]
SOIL TILTH. Most of Shuter's Indiana fields have been under no-till for 15 years, with a few over 20 years. And Shuter has been practicing variable-rate fall fertilizer and spring seeding since the early 1990s, based on a combination soil type and a grid overlay strategy. Six or seven years ago Shuter began basing his grid application rates using Veris soil electrical conductivity maps.
"We believe our success with corn on corn is a combination of four factors," Shuter says. "It starts with improved soil tilth gained from 20 years of no-till.
"With residue there for organisms to feed on and earthworms that have got that soil working, I think that's a big factor in getting consistent good yields with corn on corn."
Second is strip till, which gives a cleaner seedbed, better plant population and more uniform stand than if the Shuters were tilling all ground. Too much tillage allows residue to reduce seed-to-soil contact in the seed zone, they say.
The third success factor is triple-stack corn, which can better withstand their planting environment.
"And fourth is sidedressing our third shot of fertilizer when the corn plants need it," he says. Shuter begins his fertility program in the fall, applying a variable-rate dry blend of 5-23-30 plus manganese, sulfur and zinc when building strips. At planting he uses 10 gallons of 28% nitrogen, then sidedresses a variable-rate of anhydrous, which averages 165 pounds per acre.
LEFTOVER NITROGEN. "We currently don't treat our corn on corn any differently than our corn following soybeans," adds Shuter. "Both are strip-tilled, and fertilizer and seeding rates [26,000 to 34,000] are all the same," he says. "One aspect that's kind of unique is that we think our second-year corn may get a boost due to leftover anhydrous, since we strip-till in between old rows, which is right on top of last year's sidedress slot."
Since Mike and son Patrick use little tillage, they shred residue with knife rollers on the corn head and use residue managers on the planter to clear off the strip. "We started to strip-till six years ago when we got autosteer, and now our John Deere Greenstar 2 allows us to build strips in the fall, then repeat the same guidance in spring so the planter follows the strips," says Mike.
The Shuters haven't seen any real disease problems, despite no-till-like residue conditions between the rows. "Last summer was dry, so no disease, but there must have been some because wherever we applied strip tests with Headline fungicide, we saw an 8- to 12-bushel increase," Shuter says. Aside from using more Headline, the only other change they plan this year is seed treatment. "I think we'll use Poncho 1250 on all our refuge corn and on non-triple-stack hybrids," he says.
"We feel like we're making it all work, otherwise we wouldn't be doing it again," Shuter adds.
See next page for Corn on Corn growing tips.
[PAGEBREAK]
Tips for Corn on Corn
We gleaned tips to reduce yield-loss risks from a wide variety of university and company trials and recommendations.
They may not fit your situation exactly, but good advice exists that can be tried and tailored to your farm.
Field
- Select medium soil-texture fields with good yield history, good drainage, flat terrain, adequate phosphorus and potassium levels and a low disease/insect history.
- Minimize compaction; stay off wet fields.
- Be aware the greatest yield drag occurs under no-till.
Tillage/Residue
- Keep enough residue on the surface to stop erosion. Bury the rest in the top 6 inches where most microbial activity occurs to break down residue.
- Heavy corn residue causes cooler and wetter soil conditions, delayed seedling growth and increased exposure to soilborne diseases and insects before stand establishment.
- Handle residue in the fall. Use knife rollers on the combine head, or use a stalk chopper to pulverize residue. Bury the residue with a disk/disk ripper or move it aside with a strip-till toolbar. In spring, hit residue with a field cultivator, or just plant into your strip-till strips without tillage.
- Equip planter with residue managers to move residue and create a good seedbed for quick and uniform emergence.
Hybrids
- Carefully select the highest performing genetics with defensive traits that can handle your environment (good emergence under stressful conditions, drought tolerance, stalk strength, disease tolerance, insect resistance, etc.).
- Bt corn is a must, and most farmers say triple stacks are even better. Don't forget your refuge.
- Some experts recommend increasing plant population by 2,000 to 3,000 seeds per acre.
- Don't plant the same hybrids back to back in a field.
Fertility
- Always soil-test and keep nutrients in the medium to high range with a pH of 6.2 or greater. Pay close attention to the phosphorus level since it's crucial for early seedling growth.
- Some experts recommend calculating unused nitrogen from the previous year. Take the difference between application rate in 2007 (include nitrogen from DAP or MAP applied in the fall of 2006) and the actual yield in 2007, then reduce the rate for 2008 by half. For example, if your 2007 crop received 200 pounds of nitrogen and it yielded 150 bushels, then credit for 2008 would be half the difference, or 25 pounds of nitrogen.
- Some experts recommend an additional 20 to 60 pounds of nitrogen per acre on corn that follows corn. And they suggest two to three applications to increase nitrogen-use efficiency, especially if heavy rains hit in June.
- Organic matter shift toward heavy corn residue in soil profile can cause short-term deficiencies in nitrogen, phosphorus, sulfur and zinc.
- Use starter fertilizer for early seedling growth. Nitrogen-to-phosphorus ratio should be 1-to-1 or 2-to-1.
Disease
- Burying residue helps reduce pathogens that can lead to seedling blight, stalk rots and leaf diseases.
- Consider hybrids that show tolerance for gray leafspot, northern leaf blight, anthracnose, gibberella stalk rots and diplodia ear rot.
- Scout fields and consider an in-season fungicide application (Quadris, Headline, Quilt) at tasseling to combat leaf and stalk diseases.
- Avoid fields with previous disease problems.
Insects
- Use an insecticide seed treatment (Poncho, Cruiser) to control secondary pests (wireworm, seed corn maggot, white grub), which can cause weak plants that are more like weeds.
- Use Bt and RW traits or soil insecticide to combat the top two pests in corn on corn: rootworm and corn borer. And follow refuge acre rules.
- Remember that increased residue can boost insect pressure.
- Scout fields for cutworm and armyworm damage.
Stand
- Create a seedbed that optimizes seed-to-soil contact so corn emerges quickly, evenly and at the desired population.
- Be sure seed furrow sidewalls are not compacted (wet soil) because that limits root growth and proper furrow closure.
- If planting into soils cooler than 50°F, make sure the forecast is for warmer weather. Some experts recommend waiting until soil is in the 50 to 55°F range.
Weeds
- Increased residue can tie up soil-applied herbicides, so apply a full rate.
- Treat weeds early to minimize escapes and save yield. Unless you can be assured that your post-only herbicide can be applied by the V3 corn stage, you will likely lose enough yield to pay for the soil-applied treatment.
- Be sure to account for potential herbicide-resistant volunteer corn.
Time
- More corn acres usually result in more tillage and fertilizer passes, a tighter planting window and a longer and more complex harvest (more bushels to combine, truck, dry and store). And don't forget added labor requirements.