My favorite question so far this winter is,
“Can I get by with 0.7 pounds of nitrogen per bushel in corn?”
If you are trying to manage nitrogen by simply looking at a blanket statement of “pounds per bushel,” you will either overspend or underspend on nitrogen on your farm. Your profits will get hurt, and so may your yields.
INSTEAD, CONSIDER THESE 5 SIMPLE STEPS WE SUGGEST FOR NITROGEN MANAGEMENT.
1. MOST IMPORTANTLY, ALL CORN MUST HAVE 1.12 POUNDS OF NITROGEN PER BUSHEL.
That doesn’t mean you have to apply that much, but it does mean you have to get that much into the plant, somehow, some way. Simply multiply your yield goal on any given acre on your farm times 1.12. That’s how much nitrogen that acre needs for the crop.
For an example, let’s say your goal is 200 bushels. 200 x 1.12 = 224 pounds of nitrogen.
2. SUBTRACT CARRYOVER NITROGEN.
Let’s say your soil test says there are 60 pounds of N left from your last crop.
224 from #1 minus 60 = 164 pounds of nitrogen.
3. SUBTRACT ORGANIC MATTER MINERALIZATION.
We figure 20 to 30 pounds of nitrogen in our region for each 1% of soil organic matter. We have several fields with close to 5% organic matter. That means we have 100 to 150 pounds of N that will come available during the season. Typically, I figure on the low end, but let’s figure on the high side today.
164 from #2 minus 150 = 14 pounds of nitrogen we need to apply for 200-bushel corn.
4. ADD HIGH CARBON RESIDUE TIE-UP.
Let’s say you were in a corn-soybean rotation, but you like the corn market this year, so you decide to put a corn field back into corn. Let’s figure 50 pounds of your applied N will get tied up in the residue, at least for a year or two.
14 pounds of N from #3 plus 50 brings us to 64 pounds.
5. ADD NITROGEN LOSS.
Hopefully, you have almost no nitrogen loss, but let’s figure 20 pounds.
64 pounds from #4 plus 20 means we only have to apply 84 pounds of N for 200-bushel corn.
Here’s the challenge…
For each of the things I just listed, especially 1-3, it will vary throughout your field.
We had fields in our operation last year that had spots of 300-bushel corn and spots of 100 bushels. In those same fields, carryover nitrogen may have varied from 20 pounds to 100 pounds. Organic matter may have varied from 3% to 6%.
HOW DO YOU DECIDE WHAT TO DO WITH ALL THIS DATA???
On our farm, we’re using an inexpensive software program — VRAFY.
With VRAFY, you can pull in historic yield maps, soil test data, and even satellite imagery to estimate yield throughout each field and use actual soil test data in each area to fine-tune the entire equation. That allows us to vary our nitrogen rate throughout the field, maximizing yield and profitability, while minimizing expense and environmental risk.
Want to learn more about VRAFY and how you can use crop input data to make better decisions? Visit www.vrafy.com to get started today!
Below is an example from one of our fields showing how much we are varying the nitrogen rate.
VARIABLE RATE UREA RECOMMENDATION GENERATED IN VRAFY
For much of the last year, farmers have been asking me to help them cut their expenses. The biggest input expense on most corn farms other than seed is nitrogen, but most people aren’t looking to change much with seed and nitrogen. Usually the ask is about cutting fungicide, a biological, or going with a cheaper herbicide.
While cutting those things may “save” some money, that may also cut your yield if you aren’t careful!
Rather than that, I would encourage you to look at varying seed population and nitrogen rate. The nitrogen thing is a really big deal. While I’m not going to tell you we are seeing overapplication everywhere, we commonly see many areas in fields that receive too much N while other areas get shorted.
If you’ve never varied your nitrogen application rates before, we encourage you to start small this year. Give it a try on a couple fields, and see how it works out. On our farm, we love it, and we are now doing this practice on every acre.