Contrasting Phosphate Fertilizer Recommendations in a Corn-Soybean Rotation.
George Rehm, Univ of Minnesota, 439 Borlaug Hall, 1991 Upper Bufird Circle, St. Paul, MN 55108 and John Lamb, Univ of Minnesota, 439 Borlaug Hall, 1991 Upper Bufird Circle, St. Paul, MN 55108.
A study was conducted at the Southern Research and Outreach Center for five years to compare phosphate fertilizer recommendations derived from either crop removal or correlation and calibration. Phosphate recommendations derived from both strategies were applied on both an annual and biennial schedule. Total dry matter and grain yields were measured each year. Phosphorus uptake and P extracted with the Bray procedure were also measured. Grain and whole plant yields were not affected by fertilizer strategy used. Phosphorus uptake was affected by year, but not by recommendation strategy. The crop removal strategy produced greater recommendations for phosphate fertilization and soil test values for P increased substantially. There was a small increase in extractable P when recommendations were derived from correlation and calibration data were used. Because of added fertilizer cost with no increase in yield, use of crop removal is an expensive recommendation strategy.