By Darren Hefty
How much nitrogen does your corn crop need? How can you best determine IF you need more nitrogen this season? If so, when, and where are you going to apply it? Let’s take a look at each of these things to help you make the best decisions to maximize your crop’s performance and profitability.
First of all, how much nitrogen do you need in total for this year’s crop? Start with the Ag PhD Fertilizer Removal app by typing in your yield goal. Let’s say it’s 250 bushel corn, which needs 280 pounds of nitrogen in total. Then subtract off the amount left in the soil going into planting season. For this example, let’s say that is 20 pounds. Then estimate what your organic matter will release. This varies depending on heat, moisture, the length of your growing season, and soil microbial activity. On our farm we use 20 pounds of nitrogen for each 1% of organic matter. If your organic matter is 3%, that equals 60 pounds of nitrogen that will come available during the growing season. Factor all that together, and it looks like you need to apply 280 – 20 – 60= 200 pounds of nitrogen. If you have high carbon residue (think corn stalks) or if you are worried you will lose some of your nitrogen, you can certainly apply more. The question is, “Is whatever you apply actually enough nitrogen?”
TWO WAYS TO CHECK
While there are a number of ways to see how much nitrogen your crop still needs, here are two we use to give us confidence in our nitrogen decisions.
- Pre-Sidedress Nitrate Test – This is a $5 soil test strictly for nitrate nitrogen. I’d suggest running one at a depth of 0-12” and another one at 12-24” to see how much nitrogen is left in the soil and where it is.
- FarmersEdge Farm Command – Using their Corn Manager software you can get an up-to-the-minute estimate of your corn’s remaining nitrogen needs and a recommendation of how much additional nitrogen you may still need to apply.
Depending on what growth stage your corn is in, you can utilize growth and uptake charts to estimate how much of your nitrogen uptake is still yet to occur. For example, here is a rough estimate of the amount of total nitrogen used in a corn plant by growth stage. As you can see, approximately 35% of a corn plant’s nitrogen needs come after tassel.
- V6 – 5%
- V12 – 25%
- Tassel – 65%
WHEN AND HOW TO APPLY
Once you understand when a crop needs its nitrogen, you have a better idea on when to apply it. Keep in mind that you don’t want to overload your soil too early. Look at your CEC times 10 to get a rough idea on how much nitrogen your soil can hold at any one time.
Then it comes down to what equipment you have or would like to get in order to accomplish your applications. Keep in mind that the closer you can time the application to when the crop needs the fertilizer, the less risk of loss you have. Plus, putting the nitrogen in the soil (as opposed to on the surface of the soil) reduces risk. Those two factors are even more important than if you have a nitrogen stabilizer in the mix, although that can certainly provide some benefit, as well. Rainfall will be needed to move the nitrogen into and throughout the soil so the roots can take it in. The concept of using Y-Drops and leaving nitrogen on the surface depends on rainfall or at least the dew from the plants wetting the soil around the base of each plant.
Nitrogen is very important for your crop. Learn more right now about how much your soils are holding and how much your crop needs. It’s cheap and easy to do and may just help you make more money this year.