Rapid Depletion of Nitrogen Applied to Kentucky Bluegrass Turf

Abstract

Abstract The depletion of N applied to a moderately N-deficient Kentucky bluegrass ( Poa pratensis L.) turf was measured using a soil sampling procedure. Nitrogen as either Ca(NO 3 ) 2 or (NH 4 ) 2 SO 4 was applied in solution at 5 g N/m 2 and washed into the thatch and soil with an additional 0.3 cm of water. Both N forms were located primarily in the thatch and upper 1 cm of soil. The was present in the soil solution, while the was mainly exchangeable (86%). The concentrations of and in the soil solution were 452 and 56 μg N/ml, respectively, in the upper 1 cm of soil. Depletion of both and from the turf was very rapid, with 70% to 80% of the applied N disappearing during the first 24 hr. Essentially all of the applied N was depleted by 48 hr. Results using ( l5 NH 4 ) 2 SO 4 indicate that ≈75% of the depletion is attributable to absorption by the turf. Similar results were obtained following fertilization of perennial ryegrass ( Lolium perenne L.), tall fescue ( Festuca arundinaceae Schreb.), and creeping bentgrass ( Agrostis palustris Huds.).