Phosphorus fertilizer may not need to be applied annually to get good crop yields, according to USDA research.
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 grain yields for more than 17 years.
For best results, apply the proper amount of phosphorus the first year. Then, lower rates or skip application as needed in subsequent years, says Ardell Halvorson, soil scientist with the USDA’s Soil, Plant and Nutrient Research Laboratory in Fort Collins, Colo. Your initial cost will be higher, but it is likely to yield greater profits in the long-run.