Not too long ago a customer and I were talking about some interesting things he saw in his NDVI Imagery. He told me that he had alternating green and yellow streaking. After some discussion about this corn following soybean field, he came up with the idea that maybe this had something to do with the distribution of his soybean residue from last fall. Well, he was right. In the fall, then again in the spring, we see an uneven distribution of residue and can start to visualize the challenges that lay ahead of us. The shortlist being uneven stands due to uneven seedbed conditions.
The problem of residue distribution is the result of conditions and machine limitations. The simple fact that we spend so much time focusing on the health of the soybean plant leads to a higher number of greener stems; this adds both volume and weight, couple that with wider head widths and a faster harvest pace and you get a narrower distribution of residue. A combine’s ability to thresh soybeans significantly outpaces its capacity to get rid of residue, leaving a heavier band in the middle and lessening depths as you move out from the center.
When harvesting corn, we have an entirely different problem that has more to do with residue size and the amount of damage we do to it than it does the volume of residue present. With soybeans, we want the combine to do the work, with corn we want the head to do the heavy lifting. Here is where all the advancements in head technology and aftermarket parts come from, which are great moves forward in accomplishing our goals but it still comes down to conditions and machine limitations. When we harvest corn earlier (read higher moisture) the stalk and leaves have more moisture in them. Because of that, the head sizes it more appropriately, and it has more weight and less fluff. Most problems with corn residue come on windy days after harvest when the “fluff” moves around. The best way to mediate that problem is by running your head 12-18 inches off the ground, so the rest of the residue lays between the rows, protected from the wind.
The soybean solution seems rather simple, but it’s not. When harvesting soybeans, we need to train our grain cart operators to pay attention to the patterning of residue behind the combine. You can’t watch it from the combine, and asking you to stop is a lot, so, grain cart operator it is. As conditions change throughout the day into the evening, they can relay information to you enabling you to make changes to your settings and ground speed accordingly. Doing this will help get residue spread the entire head width a higher percentage of the day. You may have to make changes to the spreader settings a couple of times a day as things get drier then tougher again towards nightfall. When you are combining high yield beans you are going to have to find the balance between thresher optimization and spreading optimization; there will be no “perfect” just levels of better.
A final thought. Residue distribution is a problem regardless of your tillage system, short of a Mold Board plow there is no way to till your way through this. Uneven distribution of residue in a conventional or vertical tillage system leads to uneven mixing of residue and an uneven tillage depth. Which still leads to seedbed and emergence issues next spring. The success of next season’s NESP goals, nutrient cycling, and herbicide efficacy programs start with your combine, and how you address residue issues.