Sulfur Gives Early-Planted Soybeans a Jump-Start to the Season
Traditionally, most growers plant soybeans after they plant corn. However, in recent years, there has been a shift toward planting soybeans earlier in the growing season.
“Planting soybeans mid-April to early May used to be considered early,” said Mercedes Gearhart, senior agronomist at AdvanSix. “But now it’s considered timely because it allows for higher yields.”
Midwestern researchers link the yield benefit to the fact that modern soybean varieties respond to earlier planting with accelerated biomass accumulation.
“More biomass production means earlier canopy, and earlier canopy means less weeds,” Gearhart said. “Additionally, they counted more nodes per plant and concluded that delaying planting beyond mid-May results in yield potential loss of up to half-a-bushel per acre per day.”
To give these timely-planted soybeans the best chance for success, growers should pay special attention to disease history in their area as well as ensure sulfur is available to the plants from the get-go.
“Earlier planting is associated with cooler temperatures, and with that comes a higher risk of seedling diseases, so resistant varieties and seed treatments are important considerations,” said Gearhart. “Cooler temperatures also mean lower sulfur availability, a nutrient needed for nodulation and biological nitrogen fixation.”
In these cases where soybeans are planted in cool, wet soils, sulfur will likely not be available from the soil organic matter in time to boost early nodule formation. Even in cases where elemental sulfur was applied in the fall, there would not have been enough time or temperature for any considerable amount of it to oxidize into the sulfate form needed by the plants.
In fact, according to Gearhart, sources containing elemental sulfur typically take at least two or three seasons to complete the transformation to plant-available sulfate.
Therefore, supplementing with sulfate sulfur that the plant can immediately use is vital to ensuring soybean plants can thrive during this pivotal point of the growing season. With readily available sulfate sulfur, and just the right amount of nitrogen, Sulf-N® ammonium sulfate (AMS) does exactly that.
“Early in the season, you want a fast-acting sulfate sulfur source, like ammonium sulfate, in order to get nodulation off to a good start,” said Gearhart. “The small amount of nitrogen included with the sulfate often adds a couple additional bushels to what is mostly a response of soybean to sulfur given its role in biological nitrogen fixation.”
For best results, Gearhart recommends AMS be applied no more than six weeks before planting and no later than V4, or the fourth-node stage.
To learn more, contact your AdvanSix sales representative or visit soybeans.advansix.com.