Disposition of Fertilizer Phosphorus Applied to Winter Wheat1
- A. N. Sharpley2
The disposition of fall-applied fertilizer P (30 kg P ha−1) to winter wheat (Triticum aestivum L.) on four Southern Plains soils was investigated over a 4-yr period under field conditions, using 32P as a tracer. Wheat was harvested 70 d after planting and P fertilization. An average increase in wheat dry-matter yield (0.86-1.94 Mg ha−1) and Bray-1 P content of 0- 50-mm surface soil (8.4-34.4 mg kg−1) was observed following each fertilizer P application over the 4 yr. The major proportion of applied fertilizer P at wheat harvest remained in the soil as inorganic P (60-76%) with little conversion to organic P (8-15%). The proportion as Bray-1 P ranged from 17 to 51%, decreasing with an increase in P sorption capacity of the soil. With consecutive fertilizer applications the proportion of fertilizer P as Bray-1 P increased. Little movement of fertilizer P was observed below the 50-mm depth (3-7%). Recovery of fertilizer P by winter wheat decreased with consecutive fertilizer applications, ranging from 23 to 9% of that applied. The recovery was inversely related to the residual Bray-1 P content of surface soil (Bray-1 P content prior to each fertilizer application). Thus, although dry-matter yield of winter wheat increased with consecutive fertilizer applications, fertilizer P recovery decreased as residual P made an increasing contribution to uptake of P by winter wheat. Consideration of residual soil P levels may, thus, reduce costly maintenance fertilizer P applications.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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