Watch out for that first step! When producers decide to start direct seeding into standing stubble, the stumbling block they often hit is just that: the first step. Or more specifically, they often forget the first step. Like so many of Mother Nature's plans, the preparation for the big event actually begins nine months earlier. I am referring of course to residue management during the previous year's harvest, in preparation for direct seeding.
When residue is properly managed it becomes a valuable asset that can increase overall production. Standing stubble is valuable not only for trapping snow, but also for reducing wind and water erosion. Crop residues can be a critical component in the successful establishment and wintering of winter crops like fall rye and winter wheat. The residue acts as an insulating layer, protecting the vulnerable rooting systems against low winter soil temperatures.
Crop residues provide a beneficial microclimate for emerging seedlings. They also assist a young crop by providing weed suppression. Residues, through decomposition, release crop nutrients, improve soil tilth and soil organic matter content, and improve the infiltration of water into the soil profile (figure 1).
Figure 1 - Water infiltration demonstration at Scott Research Station. Comparison of a Conventional tillage field (left) vs a direct seeded field (right). Notice the difference in the water infiltration tubes during a similar time frame
Obviously crop residue can be a vital asset in a direct seeding operation. But it is imperative that the residue be properly managed to provide the benefits described. A number of factors must be considered to achieve the desired outcome.
The type of crop grown has a large bearing on the amount of straw and chaff produced. For instance, wheat or barley produces large amounts of straw but relatively little chaff, whereas canola produces large amounts of chaff in comparison to the cereals. It is important that both straw and chaff are spread adequately.
The width of cut of the combine header or the swather will determine adequate spread. In a perfect scenario, both the straw and the chaff would be spread 100% the width of cut. A more realistic goal is to have the straw spread at least 80% the width of cut and the chaff spread more than 60% the width of cut. For example, on a 25-foot header, straw should be spread back over a width of 20 feet and chaff over a width of 15 feet on each pass (Figure 2).
Figure 2 - Good straw and chaff management
An alternative to spreading chaff is to use a chaff collection system: blowing the chaff into a wagon pulled behind the combine and dropping it in piles throughout the field. Not only does the chaff provide excellent cattle feed for the winter but it also serves to remove many weed seeds off the field.
A new and emerging technology is the McLeod Harvest system (Figure 3). It uses a specially designed harvester to separate the straw from the grain and chaff (referred to as graff) in the field. The graff is taken back to a stationary cleaning mill set up at the bin site. Here the graff is separated into clean grain and millings. These millings can be used as cattle feed. The millings typically have a nutritive value equivalent to medium quality hay. For more information on this system go to www.mcleodharvest.com.
The height of the stubble is influenced largely by the method of seeding. Tall standing straw poses little difficulty for disc type seeding equipment as there is less residue on the soil surface to cause hairpinning. However tall straw can be quite another problem to hoe-type or shank-type seeding units, as straw tends to wrap around the shanks and plug the machine. For units with shank mounted packers, a good rule of thumb is to leave the stubble height no higher than 1 x the row space of the machine. For example, if the row spacing of the seeding unit is 8 inches, the stubble should not be taller than 8 inches. For hoe-type machines with narrow openers and rear-mounted packers, the general rule of thumb is to not exceed 1.5 x the row space of the machine.
Figure 3 - The McLeod harvester
It is important to remember that the most efficient and cost effective method of managing residue is at the back of the combine. A poor job of spreading straw at harvest time can be rectified by a harrowing operation post-harvest. But there is an additional cost in doing so in equipment purchase or rental, time and fuel. Chaff, however, must be managed at the back of the combine by either spreading or collection. Chaff can not be spread by a harrowing operation.
When you are planning for harvest 2001, know your goals. The planning you do today will allow you to prosper tomorrow. Remember we have a toll free number to help you make your important cropping decisions. Give us a call at 1-800-213-4287.