Corn fertility: Broadcast vs. banded vs. dry-drop

by Courtney Llewellyn

Corn yield is a product function of yield components, according to Dr. Fred Below, Ph.D., professor of crop physiology at the University of Illinois. And your yield is comprised of plants per acre, kernels per plant and weight per kernel. Producers have the most control over plants/acre, and thanks to continually advancing technology and wisdom, the average for corn increases about two bushels/acre/year.

One of those advances is banded fertility, which Below, along with University of Illinois graduate research assistant Scott Foxhoven, talked about at this spring’s Commodity Classic.

“Plant population goes up about 400 plants per acre per year, but this results in smaller roots,” Below stated. And more plants/acre means fewer kernels/plant; however, if you want more kernels/plant, you’ll see smaller weights/kernel.

“This is the challenge you’re after. It’s almost impossible to increase them simultaneously,” Below said. “But we can reverse the negative relationship with better fertilizer placement.”

So that’s what Below, Foxhoven and their research team dug into (literally). Foxhoven said they focused on the four Rs of fertility (right source, right rate, right time and right place) to try to produce both more and better corn. They used full conventional tillage and a coulter-type toolbar for planting, then compared fertilizer that was placed on top of rows vs. right below them (between four and six inches) – broadcast vs. banded fertilizer.

Corn fertility: Broadcast vs. banded vs. dry-dropDoes planting population affect corn response to fertility? Yes, Foxhoven answered, and provided the following numbers: If the population is 30,000/acre, there’s no need to band. If it’s 36,000/acre, banding can increase yield up to 25 bushels/acre. If it’s 42,000/acre, banding can increase yield up to 26 bushels/acre – but the response went down on the higher population trials with broadcast fertilizer, most likely because producers are just fertilizing the soil, not the plants. Most importantly, banded fertility has the potential to increase yield without increasing inputs.

“We can break the negative relationship between kernels per plant and plant population with that directed application of fertilizer,” Foxhoven said. He added that more yield also means more stover, but stover is not trash – it’s carbon. Having 600 pounds of stover/acre equates to about one carbon credit, for those keeping track.

Foxhoven noted that the most common criticism of pre-plant banding is that a lot of people understand that it provides superior season-long fertility, but they’re nervous about time management and think it’s an all-or-nothing approach. The research team has been working on a potential solution to in-season application beyond Y-drop application of liquid phosphorus and potassium (which could result in tank mix problems and elevated nutrient costs).

“The potential future of in-season application could be ‘dry-drop,’” Foxhoven said, which was developed at the University of Illinois. The application technology isn’t quite developed yet, but it would include a hooded vent air release air vent adapted for a Y apparatus. Dry fertilizers work because of corn plant architecture – they funnel water (and therefore wetted nutrients) directly to their roots.

In studies conducted in 2020 and 2021, the team compared broadcast vs. banded vs. dry-drop fertilization at V5 stage. From their three-site averages, broadcast fertilizer resulted in an additional nine bushels/acre; banded, an additional 17 bushels/acre; and dry-drop, an additional 18 bushels/acre.

“Yield efficiency increase doubled in banded and dry-drop – and dry-drop can be your back-up plan,” Foxhoven said. Banding is even more important when using commodity fertilizers (MAP and MOP), and surprisingly, dry-drop had similar fertilizer efficiency compared to pre-plant banding. The biggest bonus to dry-drop is that it provides more flexibility in timing and when choosing fertilizer sources. Additionally, it’s much less expensive to do dry-drop vs. liquid Y application, with the same results. As the technology to dry-drop advances, producers may want to consider it.

“Season-long fertility is crucial for achieving high yield corn,” Foxhoven concluded. “And this is done by optimizing the four Rs to break the negative yield component relationship” – increasing those kernels/plant and weight/kernel while at higher populations.

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