Submitted to: Soil Science Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/9/2000
Publication Date: N/A
Technical Abstract: Phosphorus (P) and potassium (K) soil test calibration and correlation data were developed many years ago in Louisiana. There is some concern that fertilizer recommendations based on these data are inadequate for modern high-yielding crops. The purpose of this research was to verify the accuracy of our current soil test P and K data and fertilizer recommendations. In the years 1992 to 1999, experiments were conducted with corn, cotton, rice, soybean, and sugarcane at 36 on-farm locations throughout Louisiana. Fertilizer recommendations were correct in 24 of the 36 trials (66% accuracy). Responses to P and K fertilizer did not occur when soil test P or K was rated high or very high. For the 12 trials in which recommendations were incorrect, fertilizer addition did not increase yield, even though soil test results indicated that a response should occur. Accuracy was greatest (90%) in trials with corn, and poorest (29%) in trials with soybean, suggesting that soybean yields often are affected by factors other than P or K fertility. In general, the results of these trials suggest that the current P and K fertilizer recommendations are accurate for the most of the major agronomic crops grown in Louisiana.