Effect of Rate and Placement of Superphosphate on the Yield and Phosphorus Absorption of Legume Hay

Abstract

AbstractA study was undertaken to determine the effect of superphosphate topdressing on the yield and phosphorus content of legume and legume‐grass hay. Radioactive superphosphate containing 20% P2O5 was broadcast in the early spring on established meadows at five locations in central Michigan.A significant yield response of first cutting hay was obtained on all fields as a result of topdressed applications of 80 and 120 pounds of P2O5per acre. The hay which was thus treated contained appreciably more phosphorus than did that which was grown on untreated plots or where only 40 pounds of P2O5 was applied.The absorption of fertilizer phosphorus was low in hay grown on two soils and relatively high in hay from the remaining locations. As the rate of broadcast superphosphate increased, the percentage of plant phosphorus derived from fertilizer in forage plants also increased. The recovery of fertilizer phosphorus by first‐cutting hay from two locations was low, but was as high as 15% in hay from the other areas. As the rate of broadcast superphosphate increased, the percentage of recovery of applied phosphorus decreased.The percentage of phosphorus in hay derived from superphosphate placed at various depths in two soils was related to depth of fertilizer placement. Absorption of fertilizer phosphorus was highest at the surface or 3‐inch depth; intermediate at the 6‐inch depth; and low for the 12‐, 24‐, and 36‐inch placement. In an alfalfa‐bromegrass meadow where the fertilizer was applied broadcast, the bromegrass obtained a greater percentage of its phosphorus from the fertilizer than did alfalfa. However, at the 3‐ and 6‐inch depths, the alfalfa absorbed two to three times as much phosphorus as did the bromegrass.