USDA research shows phosphorus fertilizer may not need to be applied annually to get good grain crop yields.

Phosphorus fertilizer may not need to be applied annually to get good grain crop yields, according to research from the USDA’s Agricultural Research Service.

Long-term experiments conducted on farm fields in the Great Plains found that a single application of phosphorus improved grain yields for several years. In one experiment, a single phosphorus treatment increased soil test levels and crop yields for more than 17 years.

Since phosphorus is expensive, many farmers tend to use less than the ideal amount each year. However, the research showed that economic returns were greater when the correct amount of phosphorus was applied the first year and then skipped for two or three years.

To get good results, apply a higher, adequate amount of phosphorus initially, advises Ardell Halvorson, soil scientist with the USDA’s Soil, Plant and Nutrient Research Laboratory in Fort Collins, Colo. Then, lower rates or skip application as needed in subsequent years to maintain optimum crop yields. Your initial cost will be higher, but it is likely to producer larger yields and greater profits in the long run, Halvorson says.

Since cropping intensity influences how quickly phosphorus is used, you may need to apply phosphorus fertilizer more often if using annual cropping systems, Halvorson adds. However, that doesn’t mean you need to apply it every year.

USDA Agricultural Research Service