Fertilizer recommendations proving valid even with increasing corn yields

How much fertilizer do I need for 300-bushel corn?

That’s the No. 1 question from corn producers these days, according to Glen Harris, University of Georgia Extension soil scientist.

“The easy answer is ‘a lot,’” he says. “The University of Georgia does have recommendations to take you to that 300-bushel yield. It reminds me of what happened with cotton when we used to have the old recommendation of 750 pounds per acre — now we go up to three bales.”

Harris discussed corn fertilization during the recent Corn Short Course and Georgia Corn Growers Annual Meeting held in Tifton.

For corn in Georgia, whenever you drop off your sample, irrigated base rates are 150 bushels per acre, says Harris.

“But if you read the fine print, for every 10-bushel increase, you add 12-6-10, as far as N, P and K. So if you look at nitrogen, it’s pretty straight-forward.

“For 150 bushels, we recommend 180 pounds of nitrogen per acre. For 200 bushels, you go up to 240 pounds, and for 250 bushels, go to 300 pounds. For 300 bushels per acre, we recommend more than 360 pounds of nitrogen per acre,” he says.

For P and K, it makes a difference where you’re starting from — low, medium or high, says Harris. “With a 300-bushel goal, even when you’re already high in P and K, we’re still recommending a high amount of P and K to feed that crop. Some of that is for maintenance,” he says.

But that’s only the fertilizer rate, he cautions growers.

“The latest buzz for those who work with fertilizer is not only rate but also source, timing and placement, which all come into play. You can’t think that if you put out 360 pounds of nitrogen, you’ll automatically make 300 bushels of corn.

“There are a lot of other limiting factors such as water, weed control, disease control and others, so just keep that in mind. We tend to focus on nitrogen and water as the primary limiting factors in corn,” says Harris.