I have been spending more than enough of my “free time” – whatever that is – raking leaves in my yard. A few weeks ago I was hauling a load of leaves to the landfill, and I saw windrows upon windrows in progress from being leaves and grass to beautiful compost. I thought it was funny that those very carbon sources I had been cussing were being turned into a nutrient rich resource for yards all over town. In your cornfields right now we have the same situation, we have tons of material leftover from our fields that will down the road become a great resource to future crops.
The annual amount of corn residue left over has been increasing for the past twenty years or so for various reasons, increased plant populations, reduced rotations and tillage, and other practices like the uses of Bt technology and fungicides that create healthier more resilient plants. We used to call this all “trash” but like a lot of things in the world what we call something evolves over time. This change has caused us to seek solutions for ways to handle all that residue and manage our productivity.
There is no right solution when we talk about managing residue, all of the management strategies have flaws, and all of them have merit, the trick is finding what is right for you on your farm. With that, I believe there are some guidelines regardless of management that holds true and today we are going to talk about a few of them.
When we are picking corn, our head should do about eighty percent of the residue management work, whether it being a chopping head or not the goal is to make sure the residue is evenly sized and distributed across the width of the head. A matter of fact, size and distribution is the key in all of it, so that is why it’s important at harvest. If tillage is your strategy of choice timing, depth and types of tillage are going to play a huge role in how happy you are in the spring. For example, if you were to go out with a piece of vertical tillage equipment to size the residue followed by burying it with a disk ripper all earlier in the fall while we have warmer soil temps and moisture will incorporate about 50% of the residue and speed the decomposition process for the next year. The downside is that if you missed the distribution at harvest tillage won’t make it better, it would only mix and bury it unevenly as well.
Baling of residue is another option which has both its advantages and challenges, but we see more of all the time. The benefits: the residue is removed reducing the total amount you have to work with, but removal is also the problem because we have organic matter and nutrients that we will have to replace to continue to increase the stability of our soil ecosystem. For every ton of residue, we remove we will need to replace 17 lbs of Nitrogen, 4 lbs of Phosphorus, and 20 lbs of Potassium just to maintain our current fertility and production levels. The Nitrogen one is tricky. Yes, it takes more nitrogen to break down corn residue than it does soybean residue, but once you are into a long-term Corn on Corn rotation the microbial population changes to be able to break that residue better. That 17 lbs per ton is actually late season N that the crop would have gotten from mineralization, which is arguably some of the most important N you will miss out on all year. Even though residue removal aids in the ability for the soil to warm, it causes a distribution problem. Windrowing the stalks by nature moves them and deposits them in a row, which locally may cause some emergence and vigor issues, additionally, there is added compaction risks from the added traffic.
Reduced or zone tillage. This particular set of challenges my friends is not impossible to master with discipline and patience. However, it’s where sizing and distribution are most critical. Implement setting will be the key to success or failure, and settings will change from field to field, day to day, and some cases hour by hour. With tools like hydraulic down force, cab adjustable residue managers, and proper distribution of toolbar weight all of which will help you be able to plant in higher residue conditions. Yes, the soil will stay cooler and wetter longer, but it will also allow the soil to be more resilient at times of excessive rainfall and helps the soil retain that moisture longer during the growing season.
No matter what residue management strategy you choose, it will be better to pinpoint why you are in that system before we talk about how to do it. The how becomes increasingly important when you want to talk about changing systems, and what those changes will mean to you and your operation. If we start thinking of residue as a challenge rather than a resource, then it will always just be trash to us.