As selected corn producers make 400 and even 500 bushels per acre, 300 bushels remains a lofty goal for most, and the inputs to achieve it are not insignificant.
HIGH-YIELD CORN production involves many factors in addition to sufficient fertilization.
“I think we have a decent handle on how to fertilizer for 300-bushel corn. In fact, Georgia has had recommendations for a long time, and with this resurgence among producers of wanting to go for high yields, we’ve brought those back out,” says Glen Harris, University of Georgia Extension agronomist.
Harris has tested those recommendations, with two years of data now recorded. This past year, he looked at 348 individual plots for corn research, considering variables such as nitrogen source, timing, P and K placement, and others.
“I can tell you that our high-yield growers approach it from a Liebig’s Law of the Minimum strategy. If you provide a maximum amount of inputs you’ll get a maximum yield. But usually something is not provided in an adequate amount, and it’s usually more than one thing. I can see how they come up with this strategy, but I think there can sometimes be some flaws with it. One of the flaws is that it isn’t always economical to provide these maximum inputs, so you have to be careful,” says Harris.
Water is likely the most limited factor in corn production, he says. “You also need air, N, P and K, and micronutrients. Organic matter also is important, as are heat and light. The law of the minimum system makes sense to a point. But there are things that aren’t on there that will limit you in making 300 bushels. Obviously, variety will be a key, along with planting date, and whether or not you use a starter fertilizer. Row patterns, uniform stands, and what you need for your final population all play a role,” says Harris.
Most producers, he says, have heard about the “four R’s” of fertilizer stewardship – right source, right rate, right time and right place, and all are equally important within the issue of corn fertilization.
“Also, we haven’t always sprayed corn with a fungicide, but it has become more common now, especially later in the year. So there are many factors that are not in this law-of-the-minimum strategy that are required for higher corn yields,” he says.
Harris urges growers to keep in mind realistic yield goals. “Obviously, if you fertilize for 300-bushel corn and make only 200 bushels, you’ve lost money. To be fair, you also have to look at it the other way. If you have the potential to make 300-bushel corn, and you fertilize for only 200 bushels, then you’ve also lost money.
“So what’s your realistic yield goal? I was taught you take your last five years, throw out your high and low, and then average the remaining three. The problem with that is how far back do you need to go, with rotations and everything, to get five years of corn?”
Variety choice might have changed dramatically during your last five years of corn production, says Harris.
“Basically, we’re saying if you’ve never made 300 bushels or close, but you’ve made 200, then fertilize for 250 bushels and do some of these other things. Once you’ve made 250, ramp it up and go for 300 bushels. What really scares me is when growers who have never made 100 bushels of corn start fertilizing for 300. You can get caught up in this high-yield strategy very quickly, because it’s exciting.”