Do’s And Don’ts Of Phosphorus Management

From United Soybean www.unitedsoybean.org

 

 

Farmers looking to boost yields in 2015 may want to reconsider how they manage phosphorus to ensure it’s available when soybeans need it. Doing so may boost on-farm profits and reduce off-site movement of valuable nutrients. Here are some TRUE or FALSE statements that provide the latest thinking from agronomy experts regarding phosphorus in soybeans.

 

 

 

 

TRUE: Fred Below, Ph.D., professor of plant physiology at the University of Illinois, believes pre-season phosphorus applications offer benefits throughout the season. Phosphorus is critical for root development and seed development and growth. “Soybean plants need high amounts of phosphate when they’re growing vegetatively early in the season, but almost half of that phosphorus is actually accumulated during pod fill,” he says. “Phosphorus is highly concentrated within the seeds, but to reach that point, phosphorus needs to be available throughout the course of the season.”

 

 

FALSE: Farmers should avoid the temptation of saving on application costs by fertilizing just once per corn/soybean crop rotation. University of Illinois crop sciences graduate student Ross Bender says nutrients that are left over from the corn crop may not be enough for the soybean crop. “When a farmer fertilizes with phosphate before corn, that is 18-20 months before the soybean crop needs it,” he says. “After a two-year cycle, beans often end up mining soil for nutrients.” Below adds fertilizing both corn and soybeans based on soil tests and crop-removal rates could pay through better yield. “We see a four- to five-bushel yield advantage from soybean fertilization with phosphorus over a range of soil types,” he says.

 

 

TRUE: Phosphorus tends to bond with soil particles, so the primary means of loss are soil erosion and surface runoff. “Phosphorus on the surface will attach to soil particles, which makes it susceptible to such loss,” says Bender. “Phosphorus is essential to raising high-yielding soybeans, but farmers must be diligent in managing it to ensure it is available for the crop.”

 

 

FALSE: Although some phosphorus remains in the soil after harvest, the level is minimal with soybeans. Below says soybean harvest removes 80 percent of the phosphate the plant takes up — the highest of any single mineral nutrient — leaving only 20 percent returned to the soil in residues.