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MFA Training Camp - one of MFA's many replicated trial test sites.

MFA's agronomy research provides growers with input insights

This growing season was a challenge. Across the trade territory, we barely had enough moisture to plant and establish a crop. Dry conditions persisted through the season, with only spotty showers for some fields. Our trial locations in Boonville and Columbia, Mo., were hit hard by the drought, but a few timely rainfalls made all the difference.

RainfallCardAt these locations, MFA tests both corn and soybean in many ways. Trials include our variety plots containing MorCorn, MorSoy, DeKalb, Asgrow, Brevant and NK seed brands, fungicide timing, seed treatments, nutrient use efficiency products, biologicals, plant growth regulators, fertilizers—including sulfur products—and cultural practices such as planting timing.

For this article, we will share results from our research on soybean planting date, sulfur in cropping systems, and soybean fungicide and insecticide tank mixes.

Site Management
MFA’s research site in Boonville, Mo., is 20 acres in a corn-soybean rotation. The 2023 corn trials were planted April 18 at a rate of 32,500 seeds per acre. The corn was fertilized with SuperU at planting with 280 pounds of actual nitrogen per acre. Since this is a high-yielding test site, we push the nitrogen fertilization in an attempt to eliminate the possibility of N being a limiting factor that affects yield. The soybeans were planted June 1 at a rate of 140,000 seeds per acre.

LowTempCardOur research plots east of Columbia were moved this year to a new location a short distance from our previous site. The 30-acre area will be rotated with corn and soybeans. The corn was planted May 23 at a rate of 32,500 seeds per acre. The corn was fertilized with 180 pounds of actual N per acre with SuperU. The soybeans were planted May 24 at a rate of 140,000 seeds per acre.

At both sites, all the corn research plots were planted with MorCorn 4457 except for variety trials. This has been our standard corn hybrid for trials over the past four years, allowing us to compare multi-year results more effectively because we don’t have to count for varietal differences. Similarly, we used one soybean variety, MorSoy 3965 XF, across all trials excluding variety research. The bulk of the soybeans were treated with CruiserMaxx Vibrance. All trials that include treatment of fertilizer are excluded from bulk field applications and are spread by hand. Both fields were worked prior to planting.

TimingCardSoybean Planting Date
This past year, we launched a planting date study to look at establishing soybeans each month between the same two-week window, optimizing planting conditions during that period. Originally, the plan was to start in March and continue into June. This, however, proved to be more difficult in March with rainfall almost every five days and temperatures as low as 17 degrees. Corresponding weather data can be found in Figures 1A and 1B. This trial used the same variety, MorSoy 3965 XF, at each planting timing with CruiserMaxx® Vibrance seed treatment. Planting rate was 140,000 seeds per acre, and the row spacing was 30 inches.

Dates that were most conducive for establishment each month were April 13, May 4 and June 1. There was incremental rainfall through the season with a majority coming late season from the last day of July through the first week in August. On the other hand, the low temperature did not stay at or above 30 degrees until after March 20. To explain some of the conditions around the seed at each planting, we look at Bradford Research Farm data, which is collected 14 miles away, to approximate soil temperatures at a depth of 2 inches. Soybeans established April 13 experienced temperatures of 36 degrees only four days after planting and again 10 days after planting. The soil temperature fluctuated drastically during the month of April, with only a few days having adequate warmth. Soybeans planted May 4 and June 1 never experienced soil temperatures below 50 degrees.

CornAmSulfCardWhile the drought reduced overall yield, we still captured a difference in yield of 6 to 7 bushels per acre between the May-planted soybeans and the other planting dates (Figure 1C). From the start of each planting, there was only a difference of 1.8 inches of cumulative rainfall. This might have made all the difference for the June-planted soybeans, but a majority of our precipitation came between Aug. 1 and Aug. 5, as shown in Figure 1A. These rains missed the critical stage of pod fill for our June-planted soybeans.

While this trial will be continued in the upcoming season, there are still many untold challenges to planting early. Most importantly is hitting the right timing for temperature and moisture in the soil. Starting there can fix many issues. For the best conditions, plant only when fields are CornAmSulfCardnot overly wet and when soil temperatures are at least 54 degrees, preferably 60. One shortcoming of this study could be that we did not account for early-season loss by increasing seeding rates by 10% to 20%. We also only included one maturity in this study. In 2024, the same trial is going to be implemented with two maturities. There also will be a treatment at each planting without a seed-applied fungicide and insecticide. This will help to understand the importance of soybean seed-applied fungicide and insecticide, especially when planting earlier.                       

Sulfur in Cropping Systems
Before I joined MFA, there had been two years of research on sulfur in soybeans. The interest in this topic has increased as atmospheric deposition has decreased since the 1980s. To put it into perspective, Missouri received 12.5 pounds of atmospherically deposited sulfur per acre annually in 2002. Now, the annual rate is 3 to 4 pounds of sulfur per acre annually.

When tracking the removal of sulfur on soybeans, we know that 0.45 pound of sulfur per acre is taken off in the grain per bushel of soybeans. Doing the math, that equates to 27 pounds of sulfur per acre for 60-bushel-per-acre soybeans. That means we are removing 23 pounds of sulfur from the crop residue and soil organic matter. Our only option is to replace it with fertilizers such as ammonium-sulphate (AMS), Croplex or gypsum.

For that reason, MFA conducted trials from 2021 to 2023 to understand both rate and timing of sulfur on soybeans at our Boonville and Columbia research sites. Rates were 10, 20 and 40 pounds of sulfur per acre as well as one treatment without sulfur. All three rates were applied at planting, as well as in-season at soybean growth stage V5 and R1. Our sulfur source for these trials came from AMS.

TankMixCardAnalysis included the rate of sulfur, timing of application, year, location, annual rainfall for each year, and timing of rainfalls above an inch. We found that neither timing nor rate of sulfur applied were significant. Columbia had a slight increase of 2 to 3 bushels at the V5 timing in 2021 and 2022 and an increase of 4 bushels in 2022 at 40 pounds of sulfur per acre, but there was no statistical difference when compared to plots with no sulfur applied. While our research has not found an increase in yield from sulfur being applied in season on soybeans, there are still locations in our territory that do and can benefit from these in-season applications. One example is southeast Missouri, where the prevalence of irrigation can leach sulfur, similarly to nitrogen, and can lead to a negative soybean yield response.

Though applications of sulfur on soybeans have not been proven to statistically increase yield in our research here in central Missouri, sulfur for corn acres should not be forgotten. This past year, we conducted a study using a 20-pound-per-acre rate of sulfur in the form of AMS on corn at both Boonville and Columbia. This was either applied at planting or at V5 as top-dress and included a control plot with no added sulfur. All treatments were adjusted to have the same rate of nitrogen to focus on the response of sulfur. While this study was only one year and will be conducted again, there are some initial yield responses worth sharing. As shown in Figures 2A and 2B, each site had around a 20-bushel increase from an application of sulfur at either timing. We plan to continue this study in the future to better understand this response.

According to the University of Missouri’s Dr. Gurbir Singh, Dr. Kelly Nelson and Dr. Gurpreet Kaur, there are a few considerations when trying to understand sulfur testing, recommendations and applications in corn-soybean cropping rotations. First, when testing sulfur, a tissue test will provide the most correlated data. Tissue samples may have a yield response at 25% sulfur or less. Low soil pH limits sulfur availability and reduces crop uptake. Sulfur levels can build up in the soil, and additional studies are being done to understand sulfur application carryover from corn to soybeans.

Soybean Fungicide and Insecticide Tank Mixes
In 2023, MFA’s research looked at several tank-mix combinations with Miravis Top fungicide on soybeans. These trials were conducted at both Boonville and Columbia. Application timing was either at R2 or at R4 if Endigo ZCX insecticide was applied. Treatments showcase the incremental yield gains from each product combination. Treatments and yield are listed in Figure 3A for Boonville and 3B for Columbia. We did not have a significant difference in yield at Boonville, but we did at Columbia.

TankMixCard2However, let me explain those results in terms of statistics. Our p-values (probability) were 0.08 for Boonville and 0.03 for Columbia. When running statistics, a value below 0.05 is considered significant. Those values at the Boonville location were close to becoming significant. That said, there was a numerical increase of 8 bushels from the untreated plot just using Miravis Top at this location, but additional benefits from the insecticide were not likely to be seen as few insects were found at application. The Columbia location, on the other hand, had an increase of 9 bushels with Miravis Top applied at R2 and Endigo ZCX and Trend-B, a foliar fertilizer with slow-release nitrogen and boron, applied at R4.

Both locations show that, even in a drought, there are crop health benefits to fungicide applications. Moving forward, our research will push this trial further by adding plant food and even biologicals to a list of product combinations aiming to further boost yields.

Read more from the March 2024 Today's Farmer HERE:

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