Ahh the joys of farming. One season not done, and already looking to the next. While harvest is still underway, we did want to start talking about some plans for your fall and spring nitrogen applications. In the interest of time, lets condense this down into a top five considerations heading in to 2021.
1. A good place to start is with how we determine our nitrogen rates for the coming year. Our rates are going to depend on a variety of factors, including what yield goals we have for 2021, what the weather in 2020 was like, what nutrients the previous crop used, and soil nitrate levels. We need to take account of each of these factors before we make a final determination of rate and timing for our next nitrogen application.
2. 2020 threw us some curves weather wise. In July we had more than 10 inches of rain, and some people in the county recorded closer to 12-13 inches. Our normal for the month of July is normally around 4.5 inches. It is safe to assume we saw a fair amount of leaching of nitrogen from the soil profile. (Leaching is the movement of water soluble nutrients down through the soil profile and away from the root accessible areas.) Follow this up with a very dry August and September with fairly warm temperatures and we expect that we had a fair amount of mineralization that happened. Mineralization is the process which turns organic nitrogen often in the form of organic matter or humus into inorganic forms that are now accessible for plant uptake. This was likely a bigger than normal source for the plant during the two month period because of the prior leaching of our nitrogen fertilizer in July. It’s an unusual combination of N processes to occur in a short time frame, and largely impactful on our 2021 plan. Not only do we not have residual N fertilizer left over, we have likely used up some of our organic N supply.
3. Consider taking some deep nitrate samples. Ideally, these would be at a 2-3 foot depth. This would give us the best picture of where our current nitrogen levels sit before going in to 2021.
4. Make sure you are planning your nitrogen applications for when the soil temp is below 50 degrees and will stay that way. Current 7 day average soil temps are 55 degrees at 2 inches and 56 degrees at 4 inches. We need to hold off for a while still. Don’t be following the combine with the anhydrous applicator. To be perfectly blunt, if you are applying now, you are wasting nitrogen and money. When you do get ready to apply, make sure you use a nitrification inhibitor to keep as much nitrogen stored in the soil as possible.
5. Consider splitting your application. One of the biggest concern individuals have for split applications is that they won’t get all their nitrogen on. We have a lot of options for getting N on in season that really opens up our timeline for in season applications. Consider doing a lower base rate across all acres and follow up with a spring or in season application. This can be done with side dress, pivot, or airplane with a fungicide application. We have some good options to get a split application done. We also have great tools like Granular’s nitrogen model that helps us get a better picture at what the crop has used, what impact the weather has had on our nitrogen pool, and what kind of in season rates we will need to meet our yield goals.
Those are just some starting thoughts as we start into our next field application. We’ve got some great blog posts about safety with anhydrous, 5 Considerations for Fall Anhydrous, Timing of Spring Anhydrous, and in season nitrogen applications using sensor imagery. Hopefully, these points get you thinking ahead to your 2021 nitrogen plan. Feel free to reach out to us with any questions you might have!
https://cropwatch.unl.edu/2020/planning-2021-fertilizer-n-application-following-dry-2020