With the heavy rains earlier this month we are starting to get some questions about Nitrogen loss. Today I hope to help you to better evaluate your risk and make the right decision on any type of in season Nitrogen application. First thing’s first, do not freak out, the corn crop has not and will not use a grand amount of N for about the next 2 weeks. Therefore, time is not exactly on our side, but it isn’t exactly working against us right at this moment. That being said, act deliberately to get the right information and make the right decision.
We need to understand that the Nitrate form of N is what is at greatest risk right now, and the two types of loss are leaching and denitrification. We are at risk of losing one down through the root zone into deeper zones of the soil profile and losing one to the atmosphere. The first thing we need to consider is how much of the soil N is in the nitrate form. If you applied anhydrous that conversion will take 4-6 weeks to convert the ammonium form of N to the Nitrate form after the soil warms up to about 50o F. This also holds true for the ammonium portion of your UAN solutions. If you used an inhibitor such as N-Serve or Nutrisphere-N that conversion is going to be slowed down considerably and that ammonium form is stable in the soil. If you applied Urea, it has to be incorporated into the soil where it will be converted into ammonium within a matter of a few days and become stable in the soil as well.
The second step is actually sampling to determine how much plant available Nitrogen is there and what form it is in to make the right decision on whether or not we should consider an in-season application of Nitrogen to our corn crop. Here is what our field scouts and FSA’s are doing right now to better understand the affects this heavy rainfall has had on our crops. They are taking two soil samples today in fields to send them off to the lab (Here is why we need to be deliberate!) and should get results back with in a day or two of dropping them off. They will be collecting a number of samples from the 0”-12” and 13”-24” depths to determine the N available to the plant with in the root zone. We do this for two reasons: one, to fully cover the root zone of your corn crop and two, to understand the movement of N through the root zone. We then send these samples off to the lab and have them analyze two things: the amount of Nitrate N in the soil and the amount of Ammonium N in the soil. Knowing both of these numbers should give us a pretty good Idea of how much of our applied N is left and if it is still where we put it.
The third thing we must do, my friends, is determine how much of what we applied is there, where is it and then what we are going to do about it. If you would look at Table 1 today it will show you a pretty good idea of what we applied, what happened, where did it ended up and then, with a little help, what we are going to do about it. Once we determine how much N is left, we then need to go back and reevaluate our yield potential to be sure that we haven’t had such a loss in stand that it created a significant amount of yield loss. We will also need to evaluate if our new N rate that is available going to be enough to meet the demands of that yield goal. If the answer is yes, then we don’t do anything. If the answer is no, then we have some options to get this remediated before crop demand takes off. Once again, that is why we must be deliberate in our actions.
Making the right decision here will be critical to managing your bottom line this year. If we underestimate loss and do not make any application, then we could potentially erode our yield potential and lower our profit margins. If we overestimate loss and make an unneeded application we too, could cause ourselves some issues from a profit standpoint. Therefore, being deliberate and using the right set of tools is essential to your success. I really hope this is the last article I write this year addressing the rains earlier this month. It’s time to get on to more fun topics.