A Field Comparison of Eight Phosphate Fertilizers¹

Abstract

Synopsis Differences in yields of corn from different phosphate sources were small, and in nearly all cases statistically insignificant. Fused phosphate produced a significantly higher yield of hay than any other source. Differences in yield from other treatments were insignificant. Regular grade superphosphate, concentrated superphosphate, and dicalcium phosphate produced the highest yields of potatoes; rock phosphate produced only about 60% as high potato yield as these even at double the P2O5 rate. The other materials were intermediate. Tests at the close of the experiment showed the most extractable phosphorus in plots receiving rock phosphate, fused phosphate, or calcium metaphosphate.

A Five‐Year Comparison of Rock Phospate and Concentrated Superphospate for Several Forage Crops1

“…Various phosphorus sources, usually including superphosphate and rock phosphate, have been evaluated comparatively. Rock phosphate has compared well with superphosphate in some studies ( 2,3,5) and less favorably in other cases (1,4,8), depending upon soil type and fertility, the crop grown, and numerous other factors. The results seem to indicate a higher degree of specificity for use of rock phosphate than for that of super.…”