What is in this article?:
- Extra phosphorus, sulfur, zinc can boost corn yield
- Nutrient uptake timing is key
- Subsurface banded below row
With transgenic corn rootworm hybrids’ widespread adoption, it may be time to rethink high-yield corn fertility, says Fred Below, University of Illinois plant physiologist.
Research conducted by Below and grad student Ross Bender shows that rootworm hybrids’ roots are active longer after flowering than conventional corn’s roots. This increases nutrient uptake, especially of nitrogen, phosphorus, potassium and zinc.
“We would argue that soil-fertility recommendations might be out of date for the yield goals that are achievable with today’s hybrids,” Bender says.
With the increased uptake, phosphorus is of special concern, given current fertility practices, says Below. Surveys show that on average, Illinois farmers apply just over 90 pounds per acre phosphorus in a corn and soybean rotation. Since corn and soybean harvest removes about 80% of phosphorus, Illinois soils are being depleted of phosphorus at the rate of 30 pounds of P2O5 per acre every two years, he estimates.
“This suggests a looming phosphorus-soil fertility crisis if adequate phosphorus-application-rate adjustments aren’t made as productivity increases,” Below says.
Fully filled corn ears indicate that the supply of soil nutrients — including P, S and Zn — was adequate to meet crop demand.
Nutrient uptake timing is key
Phosphorus, sulfur and zinc nutrient-uptake patterns hint at why extra fertility may pay off, says Bender, whose graduate work has focused on corn nutrient uptake. Unlike most other nutrients, phosphorus, sulfur and zinc accumulation is greater during grain-fill than during vegetative growth stages. This suggests that an assured season-long supply is critical for balanced crop nutrition and optimum grain fill, he says. In corn, half of total uptake of the three nutrients occurs after flowering. That contrasts with nitrogen, two-thirds of which is absorbed at silking.
The late-season demand for key nutrients suggests that grain yield could be lost if they are in short supply. The percentage of phosphorus, sulfur and zinc, as well as nitrogen, contained in the grain, highlights its critical nature. In the neighborhood of 60% of total nitrogen, sulfur and zinc taken up during the growing season is contained in the grain. Phosphorus tops out at 79%. In comparison, the percentage of potassium and boron in the grain is at 33% and 23%, respectively.
Among major and macronutrients, sulfur may present a special challenge. While a large percentage of most nutrients taken up by grain is mobilized from plant tissues, most sulfur in grain is taken up from the soil.