Applying dry fertilizers before planting corn, or possibly during the season, can help farmers make the most of expensive nutrients and increase yields.
Fred below, professor of crop physiology at the University of Illinois, said the current yield gap for corn is 439 bushels per acre (bpa). That’s the difference between David Hula’s world record irrigated corn yield of 616 bpa, set in 2019 near Charles City, Virginia, and the national average corn yield in 2021 of 177 bpa.
“This is your opportunity to increase your corn yield through better crop management,” Below told farmers earlier this month at the Commodity Classic in New Orleans, the most largest farmer-led agricultural and educational show in the United States.
Below, increasing the efficiency of strip fertilizers, which allows roots easier access to nutrients throughout the growing season, can help close the yield gap. It does not claim that yields will skyrocket by hundreds of bushels per acre by placing phosphorus (P) and potassium (K) in the root zone compared to broadcast applications to the soil surface, but research from the University of Illinois indicate that performance improvements may occur.
BANDAGE VS. DISSEMINATE
A 2019 study conducted by Below and Scott Foxhoven, a graduate student at the University of Illinois, compared spreading and banding of P and K before planting corn. The researchers attempted to replicate the study in 2020 and 2021, but weather issues wiped out both trials. Here are the details of the study:
- Ten corn hybrids were tested on three different plant populations – 30,000, 36,000 and 42,000 plants per acre – at a research site near Champaign, Illinois.
- One day before planting, 154 pounds of MAP (monoammonium phosphate) and 100 pounds of MOP (muriate of potash) per acre were applied. This equates to 80 pounds of P and 60 pounds of K per acre. MAP also provided 17 pounds of N per acre.
- A GPS-guided tractor pulled a coulter-type toolbar to band the fertilizer 4 to 6 inches deep into the corn rows. The seeds were planted directly on the nutrient strips. Spreading was done by a dry fertilizer spreader.
- The preplant nitrogen (N) application consisted of 280 pounds per acre of UAN32 broadcast. “We did a higher N rate to eliminate potential N effects from MAP in the fertilized plots,” Foxhoven said. “We wanted to study the response only to P and K, which are immobile nutrients.”
In the nitrogen-only control plots, corn averaged 203 bpa. In plots with diffused P and K, corn averaged 220 bpa. In striped P and K plots, corn averaged 228 bpa.
“Banding has the potential to increase yields without increasing inputs,” Foxhoven said. “Plus, it’s better for the environment than broadcasting fertilizer, which is more prone to runoff.”
There are several types of fertilizer strips. Some include directly under the seed, 2×2 placement (2 inches to the side and 2 inches below the seed), and in-season surface application next to the plants.
As farmers continue to push plant populations and adopt narrow rows (less than 30 inches apart, which is the most common row width, according to the USDA) to increase yields, here- below, the banded nutrients become even more important. The average corn population in the United States in 2021 was 29,000 plants per acre, according to the USDA. In Iowa and Illinois the average was 31,800 and 31,500 plants per acre, respectively.
Below said corn yield is a product of three components: plants per acre, kernels per plant, and kernel weight. To increase yield, farmers must improve one or more of the three components. Growers have the most control over increasing the number of plants per acre, which correlates with planting population and row width.
However, below said yield component compensation, it is difficult to increase all three functions at the same time. “It’s almost impossible to increase them simultaneously,” Under said.
For example, corn root systems shrink as plant populations increase, making it harder for plants to take up nutrients to thrive. According to University of Illinois research, corn roots weigh an average of 12.3 grams, 10.5 grams, and 9 grams per plant at 30,000, 36,000, and 42,000 plants per acre, respectively. In other words, for every 1,000 additional corn plants, root size decreases by 2.5%.
Also below, the number of grains per plant generally decreases as the number of plants per acre increases. And grain weight often decreases as grain production per plant increases. “How can we reverse these negative relationships? Better fertilizer placement,” he concluded.
In the same 2019 study of 10 maize hybrids and three planting populations comparing P and K application methods in maize, there was a correlation between yield and plant populations.
At 30,000 plants per acre, University of Illinois research shows there was no difference in corn yields between banding or broadcasting P and K before planting. At 36,000 plants per acre, P and K diffusion averaged 219 bpa compared to 228 bpa with banding. At 42,000 plants per acre, the spread of P and K averaged 217 bushels per acre compared to the band at 229 bpa.
Placing fertilizer in the soil where smaller root masses can reach it allows plants to make better use of nutrients. He said more grain was produced and grain weight did not decrease, leading to higher yields.
“We were able to break the negative relationship of the yield component…by ensuring fertility was concentrated at the start (of the growing season) and making more available later in the season,” Foxhoven said.
Indiana Farmer Randy Balls is a proponent of narrow-row, high-density maize. He and his son plant 20-inch rows and grow about 40,000 plants per acre. He said spreading fertilizer on their Lewisville operation was essential for the system to work.
Bales said the yield benefits of banding according to University of Illinois research results roughly mirror what he sees on the farm. The Bales have applied band fertilizers since 2017, when they switched to narrow rows and increased corn populations per acre by about 6,000 plants.
“Since we switched, our yields have gone from about 7% above the county average to 12% to 13% above the county average,” Bales said. “It’s a systemic approach.
CONSIDER TIME AND MONEY
It takes time to bandage fertilizer for corn production, Foxhoven said. If farmers do not already have a coulter applicator bar, dry fertilizer rig, or strip tillage machine, there are considerable costs to purchase and maintain the equipment. to also bandage the fertilizer.
Foxhoven and Bales say that increasing corn yields through banding will pay for equipment, if needed, and more.
“It’s worth it, otherwise I wouldn’t do it,” Bales said.
Foxhoven said time management is a legitimate concern for farmers considering banding fertilizer. They are concerned that all of their acres will be banded in the spring and the corn will be planted in a timely manner, given the unpredictable weather conditions.
There is a possible solution, Foxhoven said. In-season application of P and K when corn is at the V5 vegetative growth stage or later is an option for acres that have not been preplanted in strips.
In another study of University of Illinois fertilizer banding in 2020 and 2021 at three sites, researchers investigated applications of MAP and MOP to corn via preplant broadcast, preplant banding and in season at growth stage V5.
For in-season application, the researchers manually applied dry fertilizer along the base of the plants to simulate a high-clearance machine equipped with a dry fertilizer box and boom that did this, which Foxhoven called it “dry drop”. It is similar to applying liquid fertilizer in season with Y drops.
“It’s (dry-drop) a different kind of banding…we invented it,” Foxhoven said. He said the “dry” application equipment and technology is not commercially available, but he expects it to be in the near future. Foxhoven knows of farmers who have installed high-clearance machines to “dry-drop” granular fertilizers.
In the published study versus the University of Illinois banded application that includes in-season application, 180 pounds of UAN32 was broadcast preplant to all corn acres in research. MAP and MOP were applied at 154 pounds and 100 pounds per acre, respectively, by preplant broadcast, preplant banding, and dry drop at the V5 growth stage. This equates to 80 pounds of P and 60 pounds of K per acre. MAP also provided 17 pounds of N per acre.
Here are the results:
- N single control acres had an average of 235 bpa.
- The N plus the MAP and the MOP diffused in preplanting averaged 244 bpa.
- The N plus MAP and MOP in the preplant band averaged 252 bpa.
- N plus V5 dry drop MAP and MOP average 253 bpa.
“I was surprised that the dry drop had similar yields to the pre-plant strips,” Foxhoven said. “I wouldn’t necessarily recommend it as a primary application (due to environmental concerns with fertilizer runoff), but I think it could be a great backup application method if you can’t get through every acre when banding pre-sowing in spring.
Matthew Wilde can be contacted at email@example.com
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