Soil sampling depth impact on phosphorus yield response prediction in winter wheat

Nutrient stratification of no-till managed soil can affect soil test analysis levels of plant-available phosphorus (P). Research has suggested sampling to different depths due to soil acidity, but little work has been conducted to investigate any change to sampling recommendations for immobile nutrients. The objective of this study was to determine the soil sampling depth that had the greatest relationship with yield response to fertilizer-P. The depths sampled in this study were 0–5, 0–10, 0–15, 10–30, 5–10, 5–15, 10–15, and 15–30 cm. The results indicated that the top 15 cm of a soil profile had the greatest amount of Mehlich 3 extractable P (M3P) available and that the 5-to-10 and 5-to-15-cm depths had the highest correlation with relative yield. Soil depths outside of the proposed root zone of winter wheat (Triticum aestivum L.) (15–30 cm) had the lowest correlation with yield response.