Research Highlights

Can Late-Season Inputs Help Improve Soybean Yield?

By Carol Brown

When a farmer thinks about getting the most productive soybean crop, there are management considerations that can help or hinder crop growth. Fertilizers, insecticide and fungicide, soil treatments, seeding rates and row width each can contribute to improving soybean yield, depending on growing conditions. Decisions on using these are usually made and applied at planting or at early growth stages. But later in the season, when the soybean plant is working on filling out its seeds, could there be things a farmer can do to help improve seed filling and ultimately yield?

Ignacio Ciampitti, a Kansas State University Farming Systems associate professor, is asking this question as he explores ways to improve soybean yield. He is in the final year of a three-year project supported by the Kansas Soybean Commission. 

“We don’t discuss much about what happens when the plant gets to seed filling,” Ciampitti says. “When we consider the R5 stage, this is when the soybean begins to fill the seeds in the pod. We want to see what happens when we make late-season management changes to protect the plant when it is converting energy to yield and building seed quality, protein and oil.”

The crop physiologist and his research team tested soybean plots in the R5-R7 stages after treating them at R3 with fungicide, insecticide, and a combination of the two; as well as different plant nutrient options, to see which treatments, if any, improved soybean yield. In other words, he is using everything he can to protect the plant’s green area to maximize the conversion of biomass into yield and promote the formation of seed quality, he says.

“After two years of data collection, we are seeing that these different inputs were not making a substantial effect on yield,” he says. “But environmental conditions created less than optimum growing seasons.”

Ciampitti does not recommend adding these late season management inputs as they did not show a significant effect on yield, and they also add to input costs. The environmental conditions in the late part of the season seemed to play the greatest role in yield. 

But a conclusion Ciampitti did arrive at was to extend the growing season as long as possible for best results. He found that by extending the energy conversion during the late growing stages could increase yield. 

“If growers can extend the season just seven days, it could result in an additional 10 bushels/acre,” commented Ciampitti. “The entire duration of seed filling, depending on growing conditions, is around a month and a week, about 37 days. At that time, we measured yield at 61 bushels/acre. Then we compared that if seed filling was cut by seven days, the total yield was reduced to 50 bushels (Figure 1).”

That boost in yield showed the importance of seed filling and the number of days it takes, Ciampitti says. If farmers can extend the seed filling time by just a week, that could represent 10 more bushels in an environment for a yield potential of 60 bushels/acre.

This growing season, Ciampitti will collect the final year of data to confirm his recommendations. 

“I also want to test in high-yielding situations as seed weight could begin to be compromised,” he says. “If the plant has too many seeds to support, extending the seed filling time could make a large impact.”

Additionally, Ciampitti and his team will consider the effect of seed quality using these late-season inputs, as seed quality is as important as yield, he says.

Published: Jul 6, 2021