Study shows impact of sulfur fertilization on soybeans

A recent study led by Kansas State University, in the United States, indicates that the application of sulfur (S) can make a difference in soybean yield and the efficiency of nitrogen (N2) fixation by the soil.

The research analyzed 35 experiments carried out in nine North American states (Iowa, Indiana, Kansas, Michigan, Minnesota, North Dakota, Ohio, South Dakota and Wisconsin) throughout the 2021 and 2022 harvests.

The objective was to evaluate how sulfur fertilization affects seed yield and N2 fixation, in addition to understanding the impact of environmental factors, such as precipitation, temperature, organic matter and soil texture, on these processes.

The experiments compared plots with and without sulfur application. In the sulfur treatments, 34 kg/ha of the nutrient was applied at the time of planting, using granulated gypsum. The researchers also monitored several environmental variables to analyze their influence on productivity and nitrogen absorption by the plant.

Precipitation as a key factor

Precipitation during soybean development proved to be one of the most important factors, explaining approximately 40% of the variation in seed yield.

In locations where precipitation between the flowering and grain filling phases (R2 to R6) was greater than 73 mm, productivity in the plots with sulfur reached an average of 4,9 tons per hectare, with 51% of nitrogen derived from atmospheric fixation and 135 kg/ha of fixed nitrogen.

Furthermore, for both types of management (with and without sulfur), soil texture and vapor pressure deficit (VPD) were also shown to be relevant, influencing not only grain production but also the stability of these results.

Sandy soil: uncertainty in yield

Another interesting aspect revealed by the study was the relationship between soil texture and yield uncertainty.

Soils with less than 11% clay showed greater instability in yield results, while those with more than 26% clay showed greater predictability. Sandy soils, which tend to retain less water, were more susceptible to yield fluctuations, especially under water stress conditions.

Vapor pressure deficit was also a determining factor for nitrogen fixation efficiency. Under a VPD below 0,92 kPa, N₂ fixation increased significantly, favoring productivity.

Sulfur: an underrated nutrient

Although often overlooked in soybean production, sulfur has demonstrated a positive impact on both productivity and N2 fixation, especially in regions where plants demand more nitrogen.

In areas with low water retention or lower organic matter content, sulfur fertilization acted as a compensator, promoting a better plant response.

“In sandy soils, where soil nitrogen is rapidly drained, sulfur acts as a stabilizer, allowing for a better soybean response,” the researchers explained.

The study suggests that farmers could benefit from introducing sulfur fertilization into their practices, especially on sandier soils or soils with low nutrient retention capacity. It also indicates that irrigation management and attention to soil texture can help maximize the positive effects of sulfur fertilization.

More information can be found at doi.org/10.1016/j.eja.2024.127428