Quinn: Sulfur, Other Inputs Paid for Themselves with Higher Yields
Published: Friday, December 16, 2022
U.S. corn yields have increased by an average of about 2 bushels per acre per year since 1950. However, that level of annual improvement is becoming more difficult to achieve. What can growers do to keep the trend going?
Dan Quinn, Purdue University corn specialist, discussed that topic during a meeting last Friday at Dale Graeber's farm near Valparaiso.
Quinn said growers are becoming more efficient with their management practices, using the latest seed and technology, and adding additional treatments—all with the goal of producing more bushels per acre.
Corn growers this year produced 191 bushels per acre, 6% above the yield trend and the second highest yield in state history. The record, from 2021, was 195 bushels per acre.
More than just producing higher yields, Quinn said the key question is how to produce higher yields and do so economically and sustainably?
Based on field trials conducted during the 2022 growing season, the lesson learned is that the money spent on additional inputs like sulfur, fungicides and late-season nitrogen are paying off.
"Sulfur is something that I think is becoming more and more prevalent across the state," Quinn said. "If I had (to mention) one thing that I get called about the most when I start in the spring, it's sulfur—sulfur deficiency."
The field trials were set up at four locations across Indiana, along with one site near East Lansing, Mich. and another one near Lexington, Ky. One of the trials was at the Northeast Purdue Ag Center near Columbia City.
Each location featured a control (C) plot that included Purdue's recommendations for seed rate and starter fertilizer. The other test plots included the following treatments:
• C + starter fungicide (Xyway)
• C+ high seed rate (36,000)
• C + sulfur (15 pounds applied at side dress)
• C + foliar micronutrients (V6 stage)
• C + late-season (V10) nitrogen
• C + R1 fungicide (Delaro Complete)
• C + intensive (all inputs applied)
Yield data was collected from the combine's yield monitor.
At Columbia City, the control treatment averaged 221 bushels per acre, while the intensive treatment was 249 bushels per acre. The difference of 28 bushels per acre reflects a "pretty strong" response to the additional inputs, Quinn said.
Looking at individual treatments, there was a 12-bushel response from sulfur application (233.5 bushels per acre) and a 10-bushel response from the R1 fungicide application (232 bushels per acre).
The test plots in West Lafayette showed "pretty stark yield differences" between the control plot, at 199 bushels per acre, and the intensive plot, at 233 bushels per acre.
More of the same was observed at the other test plots.
"Typically, we've been seeing that sulfur application does a pretty good job, the R1 application does a pretty good job, and ... that in-season nitrogen application did a pretty good job for us this past year," Quinn said.
But how much do these treatments cost and do they improve the net profit?
According to Quinn, treatment costs (on a per-acre basis) were: control, $253; starter fungicide, $281; high seed rate, $272; sulfur, $270; foliar micronutrient, $274; V10 nitrogen, $261; R1 fungicide, $278; and intensive, $356.
Net profits at the Columbia City location were: control, $1,226; starter fungicide, $1,239; high seed rate, $1,261; sulfur, $1,285; foliar micronutrients, $1,266; V10 nitrogen, $1,224; R1 fungicide, $1,267; and intensive, $1,304.
Even with the added costs, Quinn said the intensive plot saw the highest net profit on a per acre basis.
At West Lafayette, the net profits ranged from $1,109 for the control plot to the $1,304 for the intensive. There was a 30-bushel (per acre) response for only $100 more of cost.
"The intensive treatment paid for itself," he said.
Every year is different. This year, most of Indiana experienced dry weather in June. He said the corn won't take up nitrogen if there is not enough rainfall. July saw adequate rain, and the corn really benefited from a late-season boost.
"Those late-season nitrogen applications do a pretty good job of saving quite a bit of that yield," Quinn said. "That corn's still taking up quite a bit of that nitrogen later in the season. In my experience, I've seen it recover a lot of that yield later in the season."
Weather conditions during pollination and grain fill periods are also critical, according to the Purdue expert.
Pollination is "the most critical period of a corn plant's life," Quinn said. On average, it lasts only 10 days, but that's when kernel numbers are determined. Stresses from dry weather or disease can impact silking and affect the synchronization between the pollen and silk.
Quinn said that the grain fill period is when kernel weight is determined.
Researchers have discovered that a longer grain fill period will improve kernel weight and, thus, yield.
"There's one difference we see between hybrids in the past and what hybrids are able to do now," he said. "One of the main things is just the grain fill duration. Hybrids now just have a lot longer grain fill duration."
Quinn said disease also affected this year's field trials. However, due to the dry weather early on, most of the disease pressure (tar spot, northern corn leaf blight, gray leaf spot) arrived later. He said that's where the R1 fungicide application made a big difference.
He displayed pictures of corn in both the control plot and the intensive plot. The former showed a corn leaf with lesions, while the latter had a green, healthy leaf.
"The plants are just staying greener longer," he said, referring to the intensive treatment with fungicide. "The health is a lot better in the plants as we get closer to the black layer period."
Combining the data from all the field trials, Quinn said the intensive treatment outyielded the control by an average of 24 bushels per acre.
Despite the higher costs, the intensive treatment increased net profit by an average of $115 per acre.
"Even though it cost a little more, those yield responses were able to pay for some of those products," he said.
Some of the most consistent yield responses came from sulfur, late-season nitrogen applications and R1 fungicide applications. Quinn said the fungicide application helped the leaves stay green, promoting a longer grain fill period and tacking on kernel weight.
Finally, he said there was no yield response from higher seeding rates.
"At every single site, we just did not see a yield response," Quinn said. "I think newer hybrids do a very good job of tolerating higher plant densities, but they also do a pretty good job of tolerating low plant densities, too."
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