Many growers are preparing to harvest a large crop this fall, having been blessed with ample rainfall and excellent growing conditions. A side effect of a large grain harvest in many cases is that big yields often come with big plants and large amounts of residue. Managing large amounts of residue can present challenges not only in the fall but next spring when planters begin to roll. As a result, residue can be seen as a curse, but growers also understand the value contained in those plants and are trying to take advantage of their benefits.
Each ton of residue on a 220 bushel corn crop contains approximately 100 pounds of Nitrogen, 35 pounds of P2O5 and 220 pounds of K2O. Finding a key to unlock these nutrients and make them available can help subsequent crops. Soybeans require approximately 170 pounds of K2O and 43 pounds of P2O5 to produce 60 bushel beans. In addition, 60 bushel beans require around 245 pounds of nitrogen, of which around 70-75% is fixed by the nodules, leaving the soybean plant to reap additional nitrogen from the soil.
As a practice, many growers choose not to fertilize in front of soybeans. Given the per acre need for nutrients in a soybean crop, many growers are relying on residue to fulfill some of those nutrient needs. In order to make the nitrogen and phosphorous fertility available, the plants need to break down and mineralize. Since potassium can be washed out of the stalk, having the stalks open to moisture and rainfall can make it easier to remove and wash out the potassium.
Given these factors, growers have begun to consider their combine as more than simply a harvest tool. What if the combine can be utilized to begin preparing residue for quicker breakdown and mineralization to help make the nutrients available quicker for subsequent crops? New tools are available that can help size and rupture residue which open the residue up to microbes, allowing air and water to more easily enter the stalks and begin the process of mineralization and speeding the release of nutrients.
Considering the fertility needs of soybeans, having these nutrients available following corn can be important as we try to push bean yields higher. Using the combine as a nutrient management tool may be a new way of thinking about harvesting those huge amounts of residue that will be coming in this fall with higher yields.