Availability of Phosphorus in Granulated Fertilizers

Abstract

AbstractA greenhouse test to measure the effect of placement, granule size, and the relative phosphate fixing capacity of the soil upon the efficiency of superphosphate and dicalcium phosphate was performed. The materials, labeled with P32, granulated, and sized to 4–6, 8–10, 14–20, 28–35, and −35 mesh were used in band and mixed placements on Evesboro and Davidson soils. A major difficulty encountered in greenhouse experimentation with granulated fertilizers stems from the problem of securing small samples for pot application that truly represent the test materials. Even with close‐sized materials the minimum representative sample of coarse granules is several‐fold larger than the quantity required for pot application. The test crop was wheat. Using increased yields, total phosphorus uptake, and percentage of the plant phosphorus derived from the fertilizer as criteria of agronomic value, the 14–20 mesh granules of superphosphate were the best size tested with this material while the 28–35 and −35 were the best sizes tested with dicalcium phosphate.