Soybean inputs evaluated for value

There are so many products and practices out there offering incredible benefits to crop production that is can make a farmer’s head spin. And, as crop budgets are getting increasingly tighter, it is important to know what really helps yield and what is a waste of money?

To find some answers, Laura Lindsey, with funds from the Ohio soybean checkoff, is conducting a two-year study examining some of the more popular practices and products in soybean production. Graduate student Grace Bluck also contributed to the research.

“It is a little bit different treatment design. It has been done in Ohio for corn but not for soybeans,” said Lindsey, in Horticulture and Crop Science with The Ohio State University Extension. “Similar studies have been done in Illinois, Minnesota, Wisconsin and Indiana, but not Ohio.”

The study looked at fertilizer levels, fungicides, inoculant, gypsum, and insecticides in Henry, Delaware and Clinton counties. Of the different inputs, there was very little yield response in general, though fungicides did make a difference in some situations.

“Headline was applied at R3 and that was the only treatment where we saw any yield response. When we left fungicides out, we did see yields reduced, so fungicides were doing something there. When we used fungicides by themselves, we never saw a yield increase,” she said. “We think there is some synergy between tank mixing the fungicides, insecticides and manganese fertilizer at R3 when we applied them. When we applied the fungicide Headline by itself without any adjuvant, we did not see the yield benefit. Applying something with it might improve its efficacy. Next year we are going to add a treatment of fungicide plus the crop oil according to the label.”

Disease levels in the crops were assessed two weeks before and four weeks after the treatment at three of the nine locations at Henry, Delaware and Clinton counties.

“The only two diseases we saw were brown leaf spot and frogeye leaf spot. The Clinton County location showed the largest difference in disease pressure with the treatment,” she said. “Clinton County had a 12-bushel per acre yield reduction when they left the fungicide out. There we found that brown spot had tripled in the bottom canopy. Just because you see some yield increase with fungicides, you also have to consider the economics. The five-bushel in Henry County is more on the borderline economically than the 12-bushel difference in Clinton County.”

The rhizobia inoculant was applied before planting to the seed, and led to no yield increase, and the gypsum was applied at planting.

“The gypsum is calcium sulfate and we did not see a response from the sulfur, probably because the sulfur was not deficient,” Lindsey said. “Gypsum was actually a farmer-selected treatment. Everyone was interested in it. With a one-year application of gypsum, you can’t really look at the changes in soil structure over time. The only thing we can really look at was the sulfur response. Sulfur deficiencies may become more common in Ohio because there are less atmospheric depositions from industry — less acid rain. In the future, sulfur could be more important.”

Insecticide also failed to produce a significant yield bump.

“The insecticide was Warrior at R3 and there was no response, but we did not have any insects at threshold levels where we would see a response. We foliar fed manganese at R3 and we did leaf samples,” Lindsey said. “We had no indication that manganese was deficient. There is nothing wrong with any of these products or that they were bad, they just did not increase yields because we did not see those problems in the fields.”

More observations will be gleaned from the second year of the study, but an early lesson from this work is that scouting and awareness of the field’s specific challenges is important in maximizing farm profitability.

“It is important to know what problems you have in the field before you apply anything. You can scout, or take a plant sample and see if you have deficiencies and then apply the products to remedy it,” Lindsey said. “If you don’t have the problems and you apply the product, you are just wasting money. It is better to identify the problems and go back and remedy the situation.”

Another common question Lindsey has been hearing from farmers recently concerns the benefits of nitrogen applications on soybeans.

“With higher soybean yield potential, do we need to use nitrogen fertilizer on our soybeans? In most situations, applying nitrogen to soybean has no yield benefit. Nitrogen application may be beneficial in soils with low residual nitrogen and/or low soil organic matter,” she said. “In 2013, we examined various nitrogen sources — polymer-coated urea, urea, and sulfur-coated urea — with nitrogen rates ranging from 30 to 400 pounds per acre.”

Nitrogen was either applied in a two-inch by two-inch band at planting or surface-applied at planting and R3, which was done at 10 locations throughout Ohio.

“Across all 10 locations, there was no yield benefit to any nitrogen source, rate, placement, or application timing. Our soybean yield averaged 43 to 75 bushels, depending on location. This research will be repeated in 2014,” she said. “One way to maximize nitrogen uptake by soybean plants without applying nitrogen fertilizer is by adjusting soil pH. Nodulation of soybean roots is adversely affected when soil pH drops below 6.0. In 2013, we collected soil samples from 65 farms throughout Ohio. Overall, 29% of the samples we collected had soil pH less than 6.0. Low soil pH occurred primarily east of I-71 where soils do not have as much lime content. However, there were a few areas in northwestern and western Ohio that had soil pH less than 6.0. We suggest taking a soil sample and adjusting soil pH to be greater than 6.0 to maximize nitrogen uptake by soybean.”

Lindsey said she approaches her job as simply doing and sharing the research, and not necessarily making recommendations.

“My Extension philosophy is that there are not many hard recommendations. I like to do research and explain it to farmers, then it is their decision about what to do,” she said. “Every operation is different and I just share what we did and what we saw and what they need to consider. Ultimately, it is their farm, and I just hope that I can help them make better decisions with my information.”