By Darren Hefty
You simply can’t achieve top yields in corn if you run short of nitrogen. If you over-apply nitrogen or put it on at the wrong time, you create a host of problems such as:
- Wasting money on something that won’t benefit your crop
- Depleting your organic matter
- Lowering your calcium levels
- Lowering the pH of your soil
All these things cost you money TWICE, as you will have to spend money on lime to re-build calcium and a desirable pH plus apply more nutrients each year thereafter as your organic matter is too low.
What’s the Answer?
You need to apply the right amount of nitrogen in the right form at the right time to avoid all those problems we just covered. That’s easier said than done. Here are some strategies for you to use going into this season.
Variable Rate – It makes so much sense that the best yielding areas of the field need more plant food. What is your reason/excuse not to do it? The technology to apply varying rates of fertilizer has come way down in price. Setting up your own maps to do it is not difficult either. If you need help, please ask. Variable rate is great for the environment, maximizing your yield potential, and keeping your costs down.
When to Apply N
Split Apply – Do you eat oatmeal, a hamburger, a steak, and a salad at 6 a.m. each day? Hardly. You may eat all of those things in a single day, but your body works better when you space meals out. The same holds true for your crop. I know it’s easier to apply everything your crop will need all in one shot, but do you really believe that’s the best way to do it? Ideally, applying nutrients as the plants need them protects fertilizer from tie-up and loss, effectively minimizing your expense. Using no more dollars, but just making an extra trip or two, expect more yield on average by split-applying nutrients such as nitrogen.
Pre-Plant or At Planting Time – Don’t apply more than half of your total applied nitrogen before V2. If you’re looking at applying 10 times your Cation Exchange Value at or before planting and maxing out what your soil can hold, consider this: A corn crop uses less than 20 percent of its nitrogen needs before V8 (8 collar corn). Using a nitrogen stabilizer with early season applications helps keep the fertilizer available longer into the season until the crop needs it.
In-Crop – Sidedressing is generally a good practice and allows you to apply nitrogen and other nutrients close to when the plant needs them. It will require moisture to let the plants pull the nutrients in. A new way to sidedress has generated a lot of questions, namely Y-Drops. The Y-Drop system places the nutrients near the base of the corn plants where roots are more shallow than directly in between the rows. Also, it is possible that moisture can run down the corn plant to help move the nutrients into the soil and into the plant. Whichever application method you choose, it’s important to have the nutrients available to the crop in time for the big growth spurt that happens starting at the V8 stage.
PSNT – A week or so before your in-crop N application, pull some Pre-Sidedress Nitrate Tests (PSNT) to see what’s out there. We suggest you pull 12-inch cores in the row and then every 3 inches as you move across to the next row. Blend those cores together and you’ve got your sample. Since you’re only testing for nitrate, the test is very cheap (often just $5/sample).
Mineralization – Don’t forget that through mineralization, each 1 percent of organic matter in the soil will release approximately 20 to 30 pounds of nitrogen over the course of your entire growing season (from thaw in the spring until freeze-up in the fall). If you have 4 percent organic matter soil, that’s 80 to 120 pounds of free nitrogen. If you don’t account for that somehow, you may be over-applying your N.
Brown Silk – It sounds crazy to put on more nutrients after brown silk, but Brian and I talk to farmers each week who are seeing nice gains doing just that. Oftentimes it’s just 25 pounds of N they are applying, depending on yield goal and soil nitrogen level.