Planting is under way across the U.S. Most farmers have made their decisions on variety, tillage, and other components of the planting process. However, the question remains, when should you fertigate nitrogen on corn? Fertigation is the injection of fertilizers, soil amendments, and other water-soluble products into an irrigation system.
Make Your Decision
Before you can ask when, you have to ask should you use a starter fertilizer? The answer varies. Fertigation might not be the best option every year for early applications because the crop might not need irrigation water. You simply have to decide based on what you believe will work best for your operation. While there is no right or wrong answer to this, there is an answer to when you should use it if you so choose.
Benefits of Using Fertilizer
Fertigation is an efficient method of supplying part of the nitrogen needed for a corn crop through the irrigation system, near the time of maximum nitrogen uptake.
The most noticeable benefit of starter fertilizer is increased early growth. This can sometimes be purely cosmetic though and not deliver advantage in terms of yield. Morning Ag Clips writes,
The primary benefit to in-furrow application is enhanced uptake of nutrients, like nitrogen and phosphorus, that are in short supply early in the growing season. Reduced tillage systems may have a greater benefit when using in-furrow starter due to cooler and wetter soils.
Choosing a Source
There are many options when selecting a starter fertilizer. The nutrients in shortest supply impact corn yield the most. Morning Ag Clips says,
If you want to enhance early growth, select a starter with a high P2O5 content that can economically supply 10 lbs P2O5 per acre and apply it in-furrow. This will increase growth, hasten dry down at the end of the growing season and possibly increase yield. For high residue systems, you’ll likely need nitrogen and sulfur combinations of 28 or 32% UAN with ammonium thiosulfate banded on the soil surface.
Placement options vary based on the nutrients you want apply. Nitrogen is mobile and if too much of it is placed near the seed it can reduce germination. You can mitigate this issue with placement away from the seed with at least one inch of soil between the seed and the starter band.
There is a lot that needs to be considered when planning fertigation. On sandy soils, loss potential is typically high. Additionally, snow melt, excess rain, and a crop that is not yet needing much water or nitrogen are all factors that need to be considered. These factors can cause the nitrogen to leach out because it has nothing to hold on to. Because of this, it is suggested you delay nitrogen application until the V2 stage of development.
According to University of Minnesota Extension,
After the first application, you can start to spoon feed that crop with fertigation. Research shows that doing between 3 and 4 splits starting at V2 and finishing by V12 development stages (approximately the middle – end of June) works well.
The goal is to apply just enough nitrogen to feed the crop until about the middle of June. Then you can apply the rest of the nitrogen needed for the crop. After that time, loss potential is low because there is usually no excess moisture.
Important Fertigation Considerations
There is little to no advantage to keep applying nitrogen after the V12 growth stage. In tests, yields were similar when fertigated between the V12 stage to tassel. Therefore, there is no need to waste time after the V12 stage.
You also do not want to be in a situation where you have not applied enough nitrogen when the crop needs it. When you fertigate, you give the crop a little nitrogen at a time. In June and July the crop will need more nitrogen because of the biomass it is putting on.
It is also important to remember too much of any starter can present risks for stand damage.
Also, be sure to consider the amount of water you are putting on. Tensiometers, irrigation scheduling, or doing a hand moisture test are all ways to track how much water the soil needs for the crop. Nitrate moves with water, so you increase risk of nitrogen loss if you irrigate when your field is at capacity.
There are many considerations to keep in mind when looking at corn fertigation. First and foremost, you need to consider whether fertigation is the best option for you. You also need to consider if you want to use nitrogen or if another source would better suit you. You then need to consider placement and timing of fertigation as well. Also, be sure to monitor the amounts of water you are using.