Study Investigates Effect of Manure on Soybean Ground

Results of an important research study conducted by Penn State University to determine if manure applications to soybean ground had any effect on the incidence of disease, weed pressure, soil nitrate levels, nodulation and yields indicate that applying manure at lower rates will result in neither a positive nor negative impact on the crop.

The study indicates that manure could be applied, if necessary, to supply phosphorus and potassium to soybeans without negatively affecting the crop. It also shows that applying nitrogen to the crop through manure does not lead to nitrogen loss through leaching, nor does it hurt the soybean plant’s nodulation.

“Although there has been some research done on this topic in the Midwest, little research has been done in Pennsylvania to determine if manure land applications positively or negatively affect soybean yields,” says Penn State Extension educator Del Voight, one of the investigators in the study. “Soybeans are becoming an integral part of crop rotations throughout Pennsylvania, and many farmers rely on their soybean ground to provide the amount of land needed for their manure applications.”

The three-year research project study was funded by the Pennsylvania Soybean Board through the soy checkoff.

The study involved three separate field locations, where three different types of manure were applied: liquid dairy manure, liquid swine manure and spread turkey manure. Overall, researchers noticed no connection between applying manure with increased weed or disease pressure.

“One of the concerns with applying manure to soybeans is the increased incidence of white mold,” says Voight. “No evidence of white mold was found during scouting of the plots. However, it is important to note that the three fields in this study did not have a history of white mold.”

Courtesy Pennsylvania Soybean Board

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