Variable-rate Phosphorus Fertilization: On-farm Research Methods and Evaluation for Corn and Soybean

This study adapted precision agriculture technologies to commonly used field-scale strip trials and compared fixed and variable phosphorus (P) fertilization for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Differential global positioning receivers, yield monitors, and grid soil sampling were used. Variablerate fertilization reduced considerably the total amount of P fertilizer applied in two of four fields and increased yields in one field. Statistical analysis that accounted for spatial correlation of yield improved the evaluation of treatment effects. The results showed that a combination of traditional on-farm strip trials, precision farming technologies, and statistical methods that account for spatial correlation of yields can be used to obtain more thorough comparisons of management practices.