If a Martian farmer parked his spaceship in the middle of the Corn Belt this spring, he'd likely think every farmer had gone to no-till from all the untouched crop residue. Of course, what really happened in many areas was a wet spring in 2009 followed by a cool wet summer and fall and a harvest that dragged on until Christmas or even later.
"Last fall we did more tillage with combines and grain carts than we did with tillage tools,” says Ken Ferrie, Farm Journal Field Agronomist. "What we have out there is a big mess.”
What to do now? This spring, you'll need to cope with a variety of problems, maintain yields as much as possible and work soil back into shape as time permits—a process that could take several years.
Your spring decisions will include what to do about ruts and wheel tracks; what kind of tillage, if any, is needed; how to manage residue with your planter; and how to pay the carbon penalty caused by undecomposed residue.
"If we don't take care of these issues as we come out of the gate, we're going to see some of the toughest corn we've seen in a long time,” Ferrie warns.
Ruts and wheel tracks.
"Anything deeper than 3" is a rut, and this year we are seeing ruts 2' or more,” Ferrie says. "In most years, farmers can plant through wheel tracks, but when the lug marks are 3" deep that makes it tough to plant into. This is especially true when planting corn 1½" deep into a
3" wheel track. Wheel tracks in the field must be managed.
"I have had a number of farmers call and say they are glad they're no-till because their neighbors who do tillage are sinking. But 3" deep wheel tracks in no-till can be just as big of a problem as ruts that are 1' deep in conventional tillage.”
Depending on where the ruts are, how deep they are and how many of them there are, you probably will have to do some tillage. If ruts are in highly erodible ground, be sure to check with your county Farm Service Agency.
"Before you till,” Ferrie adds, "map those ruts. It will take up to three or four years to fix some of the compaction we created, so you must remember where they are.”
Look for chances to do shallow vertical tillage yet this winter, but for many the time window may be gone.
"I would avoid doing deep tillage 14" or 15" deep in the spring,” Ferrie says. "Deep tillage could dry out the soil too much; or, if you get rain, it will turn the soil into a sponge that could stay wet for weeks.
"Use a chisel plow with shanks on 14" centers, 6" or 7" deep, to fill in ruts and tear out tracks. You want to do a good job of surface shattering without going deep. You do not want columns of unworked soil extending all the way to the surface if you are following with a vertical tillage harrow.”
If you did shallow chiseling this past fall (because the soil was too wet to run deep), check for those columns of soil this spring. If you find them, shear them off with a soil finisher or similar horizontal tillage tool to create a seedbed to plant in.
You want to do spring chiseling as far ahead of planting as possible—but only in dry conditions. "You can get by chiseling wet soil in the fall, when you have freezing and thawing to reset the soil,” Ferrie says. "But there's no such margin for error with spring chiseling.
"It will be toughest in corn-on-corn, in which stalks must dry out. In that situation, don't rule out the moldboard plow if soil is not subject to erosion.”
In most cases with spring tillage, you must level within three or four hours to prevent clods from forming. "Have a leveling crew running right behind your chisel,” Ferrie emphasizes.
Remove fluid from tires and reduce weight on the tractor. There will be no freezing and thawing to remove the tracks you make while tilling this spring.
Minimize dense layers.
If you normally no-till corn into soybean stubble but your fields are crisscrossed by wheel tracks, resist the temptation to "fix” them by disking 2" or so deep. "You risk creating a dense layer just under the surface,” he says. "That layer will stop corn roots hard. The closer a dense layer is to the soil surface, the more problems it causes.”
That advice also applies to conventional-till farmers who were unable to get their tillage done this past fall and are considering implementing no-till for the first time. "If there are tracks more than 3" deep, take them out before planting,” Ferrie advises.
Moldboard plowing and horizontal tillage tools create a density layer that will have to be fixed later, Ferrie says. But for now, you just want to create a seedbed to plant in. In your worst rutted fields, consider planting a shorter-season hybrid or soybeans so you can harvest earlier and do corrective deep tillage in the fall.
An option not involving horizontal tillage is spring strip-till to take out wheel tracks and create a seedbed.
"Be careful with anhydrous ammonia on the strip-till pass,” Ferrie advises. "I've seen 70 lb. of ammonia per acre, applied as early as February, smoke corn that was planted over the strip. However, you can apply phosphate and potash. You can also apply some 28% nitrogen solution—but not too much because too high a rate of solution can burn corn, too.”
When spring strip-tilling with a mole knife, you need to build the strip early to leave as much time as possible before planting.
"It would be ideal then if a 1½" rain came to settle the strip,” Ferrie says.
No ruts but no tillage, either.
Some conventional-till farmers may find themselves without ruts or wheel tracks but no fall tillage completed. "If you're planting corn into soybean stubble, consider no-tilling because there is less risk with that than with spring chiseling,” Ferrie says. "You could aerate the soil with a harrow to make no-till planting easier.”
If you're planting corn on corn, spring strip-till as described above is an option. "But by the time stalk ground is ready to strip-till, it may also be ready to plant,” Ferrie says. "You can also no-till, but expect to pay a yield penalty with no-till corn on corn. Even with the yield penalty, corn may cash flow better than soybeans.”
All these measures come with trade-offs, such as increased disease pressure because of more residue carried forward. But the goal is to grow the best crop you can this year while setting the stage to get back into your normal program as quickly as possible, whether that is conventional tillage, vertical tillage, no-till or strip-till.
Set up your planter
. Equipping your planter to deal with your new tillage situation is critical. If you're a no-till farmer using tillage this spring, remove your no-till coulters.
"You only need a coulter for two situations,” Ferrie says. "One is to cut residue and the other is to do tillage. In sandy soil, you may want to cut the residue and plant through it so you can maintain the residue cover to keep plants from being cut off by blowing sand. There are some situations in which you need to do some tillage in front of the disk opener so the opener will work properly. In that case, first move the residue out of the way with a row cleaner ahead of the coulter.
"But in tilled ground, whether conventional tillage or vertical tillage, a coulter will only shove residue into loose soil and tuck it around the seed.”
If you are a conventional-tillage farmer who is going to no-till for the first time because of a lack of fall tillage, you will need a coulter or an aggressive row cleaner placed in front of the planting unit to prepare the soil for the disk openers.
Without row cleaners, residue bunches over the row, creating cooler wetter conditions. It also makes a microenvironment at the base of the plant for microbe populations to surge and immobilize nitrogen making it temporarily unavailable.
Ferrie's studies show floating row cleaners are more consistent than fixed row cleaners in clearing residue. Floating row cleaners follow the contour across a field, cleaning a uniform strip. Fixed row cleaners will rise above the surface if the planter unit floats out of the ground.
Down pressure must be set to match planting conditions. Adequate down-pressure settings for no-till will be excessive in a tillage situation, leading to sidewall smearing, Ferrie says. "If in doubt, err on the heavy side to make sure your planter doesn't come out of the ground, but use no more down pressure than necessary.”
No-tillers may need to remove their spiked closing wheels if they plant into a spring-chiseled seedbed that has a higher risk of drying out; conventional-tillage farmers will need to add spiked closing wheels if they are going into tougher no-till conditions.
"The function of cast-iron or rubber closing wheels in tilled conditions is to compress the soil above the seed and take out the air pockets,” Ferrie says. "They make soil conditions uniform and prevent water from evaporating off the top of the seed faster than it comes up from below. Spike wheels are designed to crush the sidewall in and prevent sidewall smearing in no-till conditions. But in tilled soil, they may not firm the soil well enough to keep it from drying out. This is a bigger concern in 2010 where spring chiseling is done to manage ruts when there's a greater risk of drying out. It may not affect overall population if the furrows dry out, but it could give us ear count problems.”
Drag chains are beneficial in no-till and tilled conditions. "When setting up your planter, consider soil type and conditions in each field,” Ferrie adds.
How effectively you manage old-crop residue greatly influences how good a crop you grow. The microbes that decompose old-crop residue temporarily tie up nitrogen, so plants can run short unless you take corrective measures.
Residue decomposition is closely tied to temperature. Depending on where you farm, decomposition may start in the fall. But with a late harvest, most of this will happen in the spring. Corn residue, due to its amount and makeup, takes considerably more time than soybeans.
When soil microbes decompose carbon, they consume nitrogen in the soil, "immobilizing” it into the organic form so it is temporarily unavailable to the plants. You can manage around this situation and keep plants from going hungry by managing the timing and placement of your nutrients.
If corn follows corn under normal weather conditions, research from the Farm Journal Test Plots in central Illinois suggests, it takes 100 lb. of nitrogen per acre in the top few inches of soil to keep it green. Part could be applied in the fall and the remainder in the spring. (The nitrogen counts as part of the total requirement for the crop—you don't change the rate, just timing and placement.)
If your goal is to drive decomposition faster, apply a portion in the fall and the balance in the spring. If you want to maintain or slow down decomposition, put it all on in the spring.
This spring, you will be incorporating large amounts of crop residue because less was decomposed this past fall. "With spring tillage, you may need to move 30 lb. or 40 lb. more of your nitrogen program to a spring surface application,” Ferrie says.
The amount required could be more or less depending on the volume and type of residue in the field. That is influenced by whether you're dealing with corn or soybean residue, tall or short varieties and high or low populations. If you till, try to incorporate the residue as far ahead as possible to give microbes more time to decompose it, Ferrie says.
If you have a long-term no-till field going to tillage because of tracks or ruts, you will pay a bigger carbon penalty than normal because you will be incorporating carbon that has built up near the surface. That means you need to surface-apply more nitrogen.
"I like to see some of the surface-applied nitrogen in the nitrate form. Liquid 28% or 32% nitrogen solution is a good choice because it contains both nitrate, for the plants, and ammonium, which microbes prefer,” Ferrie says. "Nitrogen applied with the planter will be twice as effective as broadcast nitrogen because it is positioned where roots can reach it and microbes can't.”
Fortify against disease.
"With tillage delayed until spring, anticipate more pressure from foliar diseases because you will have more crop residue, in which fungi overwintered,” Ferrie explains. "Make sure you don't follow a hybrid that was susceptible to diplodia or other ear rots with a similar hybrid in 2010.”
Farmers should plan to manage for ear molds for the next several years. "Because many farmers have not been able to do normal tillage and bury residue for several years, they have lots of inoculum built up,” Ferrie says. "Inoculum can also come in from neighboring fields.
"If a field had ear molds last year and you no-till soybeans this year, the inoculum will still be present in 2011,” he says. "Corn-on-corn in no-till and strip-till are the toughest disease situations of all, especially if you grew a susceptible hybrid that produced a lot of inoculum.
"In this scenario, hybrid selection becomes very important. Resistance to diplodia is easier to find, but talk to your seeds person so he or she can recommend hybrids with good scores on fusarium and gibberella, as well,” Ferrie adds.
Stay calm, be patient and think every action through. Spring 2010 is going to be an exciting ride.
You can e-mail Darrell Smith at firstname.lastname@example.org