Providing enough nitrogen, phosphorus and potassium are crucial for high corn yields, but in order to really maximize production, these nutrients need to be in the proper ratios.

Purdue and Kansas State universities reviewed more than 150 corn studies spanning 100 years in the U.S. and other regions and found that specific uptake ratios of N, P and K were associated with high yields — regardless of where the corn was grown. 

“The highest corn yields, if there are no other limiting factors, are when nitrogen and potassium uptake is in a 1-to-1 ratio and nitrogen and phosphorus uptake is in a 5-to-1 ratio,” says Ignacio Ciampitti, a crop physiologist and nutritionist for Kansas State University. “Having the right nutrient balance within plants is more important to increasing yields than just applying extra nitrogen.”

He explains that these ratios apply to aboveground portions of the corn soon after physiological maturity. At other growth stages, they’re different.

Based on these findings, growers need to be as concerned about the amount of K available to their plants as they are about N, says Purdue University agronomist Tony Vyn.

“Corn’s demand for nitrogen and potassium is similar,” he says. “We need to focus on the nitrogen-potassium balance because that’s where we have the greatest deficiency in terms of application, especially in the eastern Corn Belt.”

Ciampitti says corn absorbs about 80-90% of its total season K amount by the flowering stage, but only 50-60% of its total season N uptake. As the season progresses the ratio gets larger, so by maturity the ratio is 1-to-1.

The opposite occurs with P — accumulation is greatest later in the season. Vyn says corn accumulates most of the P in the kernels, and the proportionately later P uptake means the N-to-P ratio declines as the season progresses. Ciampitti adds that corn yield level is not strictly related to the N-P balance, but in high-yield-potential systems, the 5-to-1 ratio is the best.

While focusing on nutrient balance will help increase corn yields, Vyn and Ciampitti say that an integrated approach to corn yield improvement that includes genetics and management is key to making it happen.

To learn more, see the paper “Understanding Global and Historical Nutrient Use Efficiencies for Closing Maize Yield Gaps,” by Vyn and Ciampitti in Agronomy Journal.