Have Wheat, Need tillage - But how much?
By Greg Stewart, OMAFRA Corn Specialist

There is a balancing act between reducing tillage, leaving wheat straw in the field, and optimizing next year’s corn yields. The impact of this balancing act is highlighted by research done by the University of Guelph (see Figure 1). Complete straw removal goes a long way to boosting no-till yields so that they are similar to those obtained with the moldboard plow. European experience certainly supports this idea as well. There, the expansion of no-till - even within a cereal following cereal rotation - was very rapid providing you could burn off the previous year’s straw. When straw burning was stopped, no-till hit a wall.

Under Ontario conditions, if you leave a large percentage of your wheat straw in the field on fine textured soils, some tillage seems almost mandatory in order to reduce the risk of poor stands or poor growth in next year’s corn crop. A frequently asked question is whether returning all the straw to the field and moldboard plowing is better for the soil than cutting the wheat short, baling the straw and planting corn no-till. If you farm where the risks of water and wind erosion are near zero, the benefits of returning all the straw might outweigh the advantages of reducing tillage. But for the majority of farms in Ontario, removing some straw to allow for the erosion protection and soil-building benefits of reduced tillage is almost certainly the better option.

The other point to consider in this discussion of burying wheat straw is the potential of using a system where wheat fields are lightly disced in the fall (approx. 3” deep), left level, and then corn is planted in the spring without any further tillage. Yields under this approach have been very consistent year to year and very close to those obtained with traditional moldboard tillage. This system can handle considerably higher wheat straw levels than no-till, and still represents considerable cost savings over conventional tillage.

The ability to use a disc as your fall tillage tool following wheat harvest will depend on what type of disc you have. The older, lighter-weight finishing discs generally perform too inconsistently from year to year or field to field to be considered a reliable option. However, the new age of heavier discs has solved many of these penetration problems. Harry Buurma of Lambton County, for example, has wrestled for years with the balance between wanting to leave as much straw as possible to build the organic matter in his soil, and doing as little tillage as possible. His most recent move in this progression has been to purchase an off-set disc designed to handle all of his primary tillage needs following wheat as well as incorporating his manure. The 18’ disc (Sunflower, 1300 series, 24”blades, 8.5” disc spacing, total weight of 9132 lbs) allows Buurma to get the tillage operation completed soon after wheat harvest is completed. Buurma likes the idea of intentionally blowing an extra bushel of wheat out the back of the combine to act as a cover crop, but sees this system working far better when tillage is on time and at a uniform depth across the field.

One of the other advantages to fall discing, or any fall tillage system that leaves the soil level, is the opportunity to reduce spring tillage significantly. Buurma has been looking at reducing spring tillage for some time now. A few years ago, he purchased a Phoenix prickle bar rolling harrow with the idea that all he might need to do after wheat is to ‘fluff’ the wheat straw to get the field to dry out in preparation for no-till planting. Harry concedes that this has not worked quite as well as planned, that is, the corn intended for heavy soils stills gets overly delayed by wet soils even with the use of the rolling harrrow.

He is quick to point out, however, that if you can do a uniform, level job of fall discing, the Phoenix makes for a high-speed, low cost spring tillage option that works on all but his heaviest soils.

Most growers need to ask themselves why they are choosing particular tillage options. For Harry Buurma, the answers revolve around improving profits, reducing tillage costs, and managing residue to build soil health. He freely admits that for him it has little to do with getting the highest yields possible.

The disc versus the disc-ripper
I had lots of good discussions at the most recent Outdoor Farm Show on the value of the disc versus the disc-ripper as primary tillage tools. Certainly research work in the province has often shown the disc to be more efficient than a chisel plow and often does a better job of leaving the soil surface level and easier to manage in the spring. In addition, our work with in-row deep ripping has shown very little advantage in corn yields over shallower tillage depths. But the reality is that we do not have a good set of comparisons between the disc and the disc-ripper in terms of yield improvements as a result of the deep tillage associated with a disc-ripper. If you have some feedback on this question or would be willing to work with me in setting up some of these trials, give me a call at 519-824-4120, Ext. 4865 or e-mail at Greg.Stewart1@ontario.ca.

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