Disks Stage a Comeback

Nov 1, 2006 12:00 PM, By Jodie Wehrspann

In the midst of a cyclical downturn in tillage sales, there's one tool that is gaining ground: disks.

Growers are adding disks, or disk harrows, to their toolbox to tackle tougher corn residue, a growing problem on Midwest farms.

“One of the trend lines we are seeing is residue management,” says Larry Kuster, marketing specialist for AGCO Sunflower. “And we can debate about strip-till, no-till and other farming practices, but we are all working with genetically altered crops now.”

Kuster says that while genetically altered crops produce higher yields they also leave more residue. The average amount of residue on a 200+ bu. cornfield today is 5 tons/acre compared to just 2 to 3 tons/acre less than a decade ago.

The plant cell walls contain lignin, a chemical compound that holds the plant cells together. The lignin in genetically modified hybrids doesn't break down over winter as easily as the lignin in conventional hybrids. “We started seeing the problem eight years ago with Roundup Ready beans and Bt corn,” Kuster says. “Farmers were complaining that residue wasn't passing through their harrows, and they wanted us to adjust the implements. We quickly found we were dealing with a different plant.”

In addition, farmers are growing more continuous corn acres as opposed to using the old corn and bean rotation. The end result is a growing stockpile of stalks and stems that can interfere with planting and form a hotbed for disease.

Break it down

To deal with the different and tougher plant, growers have started using disks again. “In the past there hasn't been as much need to size the residue,” says Kail Schoen, marketing manager with Landoll Corporation. “Farmers used to do more standard ripping or chiseling in the fall and then hit the field with the cultivator in spring.”

Unlike other tillage tools, disks are specifically designed to cut residue down to manageable chunks and mix it into the top 4 to 5 in. of soil. Wide rows of circular blades do the cutting and mixing. The top few inches of soil form the zone where soil microbes are the most active to allow for decay.

“We like to reference a wooden fence post,” explains Jamie Meier, Landoll's ag division sales manager. “Where does a fence post rot? Always right below the soil surface because there is air, soil and moisture, which make the microbes most aggressive.”

For the residue to decompose, it must be incorporated in the ground before the soil temperature drops to 40° when microbes go dormant. Disks are sized wide, covering 30 to 40 ft. in a pass, allowing you to meet that window. “Compared to a smaller ripper-type tool, you can get in the field and cover a lot of acres quickly, which is especially important further north in the Corn Belt,” Meier says.

Manufacturers recommend you disk as soon as possible after harvest before the soil temperature drops. Once the residue starts breaking down, the soil gets a kickback in nitrogen. The available nutrients on an acre of 200-bu. corn translate to 77 lbs. of nitrogen, 12 lbs. of phosphorus and 116 lbs. of potassium if the residue is sized and incorporated in the soil. The additional nitrogen can help offset the cost of fuel required to make a disk pass.

Disk usage is bridging all tillage classes — from conventional till to no-till. “The disk harrow is one of those tools that no matter what your tillage beliefs are you are probably still going to have a good disk harrow,” says Tom Evans, vice-president of sales for Great Plains Manufacturing, a company specializing in conventional and vertical tillage tools. “Even if you are a firm believer in vertical tillage, you can still disk afterward or use a disk prior to subsoiling without changing the soil density.”

Evans says disking is one of the fastest and most efficient ways to chop residue and smooth out combine ruts.

Landoll's Meier says conventional tillers are doing a disk pass prior to running the traditional coulters, chisels or disk rippers. No-till farmers, on the other hand, are using the disk as their only tillage pass.

Cuts across classes

“To give you an example, we just talked to some no-till guys who are looking at buying a disk to get rid of residue,” Meier says. “They plan to disk in the fall and plant on a stale seedbed. They still consider themselves to be practicing no-till because they are not making a secondary pass in the spring.”

He says disks can help no-tillers with other challenges, too, like slow soil warm-up and uneven emergence, by leveling the ground and incorporating the residue so the planter can penetrate the ground more evenly.

Downsides of disking

On the downside, disking may not work equally as well in all soil types. It also leaves less residue cover than no-tilling, which makes the soil more susceptible to erosion. However, tillage manufacturers say that, in this new cropping environment, no-till farmers, including those who are switching to strip-till, will need to do something to handle residue, especially if they are looking at using a corn-on-corn rotation.

Disking also does not address soil compaction, which occurs deeper in the soil profile. Growers concerned about compaction will have to make a separate pass with ripper-type shanks to fracture compacted layers.

David Benson, spokesperson for Krause Corporation, says that, because compaction is an issue of many farms, disk ripper combination tools also have been a hot item this year for his company.

“When talking with customers about their fall tillage needs in cornstalks, I advise there are basically two scenarios depending on your soil management needs,” Benson says. “One is if you have deeper compaction you'll need to size and incorporate residue and address the compaction with some type of deep tillage. Then I recommend a one-pass combination primary tillage system like the Krause Dominator. If sizing and incorporating residue is the main goal, then a tandem disk harrow is the higher speed, higher productivity way to go.”