Evaluation of incorporated phosphorus fertilizer recommendations on no-till managed winter wheat

The current Oklahoma State University Soil, Water, and Forage Analytical Laboratory (OSU) phosphorus (P) recommendations were developed for conventional tillage systems with P fertilizer incorporated in the soil. The rate recommendations were based on a sufficiency approach, and included a pH adjustment factor. Increased adoption of no-till (NT) management across the region has resulted in more surface application of fertilizer, without concomitant changes in OSU recommendations. In the 2014-2015 and 2015-2016 growing seasons, nine on-farm trials were conducted in north-central Oklahoma to evaluate current winter wheat (Triticum aestivum L.) P recommendations, and grain yield responses to fertilizer in both P-sufficient and P-deficient soils, and acidic or non-acidic conditions. Phosphorus fertilizer was recommended for eight of the nine locations, while responses were recorded at only five of those eight locations. The results indicate that OSU P recommendations, with a soil acidity adjustment factor, did not limit winter wheat grain yields in NT management. In addition, the application of 30 lb acre(-1) P2O5 offset the effects of soil acidity on P uptake regardless of the degree of acidity. Finally, OSU recommended P on some locations where there was no response, suggesting more work is needed to understand crop response dynamics and build recommendations with increased location specificity.