Plant‐available soil nitrogen fluxes and turfgrass quality of Kentucky bluegrass fertilized with humic substances

Abstract

High quality turfgrass requires adequate amounts of nitrogen (N) fertilizer. However, excess N application can increase N losses via leaching and gaseous emissions. Enhanced efficiency fertilizers (EEFs) and humic substances have been used to decrease N losses to the environment. A two-year field experiment was conducted on a native soil with Kentucky bluegrass (Poa pratensis L.) to investigate if the addition of humic substances to fertilizers This article is protected by copyright. All rights reserved. could be classified as an enhanced efficiency fertilizer (EEF). To determine this, the objectives were, 1) to determine if incorporating humic substances will increase the plantavailable N collected on ion exchange membranes (IEM) over a growing season, and 2) to determine the N release (NR) curves of the fertilizer treatments using the mesh bag technique. Fertilizer treatments included humic-coated urea (HCU), poly-coated humiccoated urea (PCHCU), urea + humic dispersing granules (HDG), poly-coated sulfur-coated urea (PCSCU), stabilized N, urea, and a nontreated control. Overall, the addition of humic substance to fertilizers did not improve turfgrass quality compared to fertilizers alone.Additionally, all fertilizer treatments had improved turfgrass quality relative to the nontreated control and provided acceptable turfgrass quality for almost all of the growing season. Over the growing season, PCHCU had 25% greater inorganic N captured on IEM compared to all other treatments. Both PCHCU and PCSCU show extended NR curves with PCHCU having a greater release period. In conclusion, PCHCU increased plant-available N concentrations, released it slowly, and should be classified as an EEF.

Temporal Recovery of Polymer-Coated Urea-N by Kentucky Bluegrass in the Field

“…The fate of nitrogen in fertilizers applied to turfgrass is the subject of great horticultural interest. Extraordinary field research effort has been applied to accounting the mass balance and fate of applied fertilizer N [48][49][50][51]. While the research described herein directly quantified only assimilation and vegetative investment of fertilizer N via offtake, indirect inference of the conjugate may afford the reader greater appreciation for the treatment array employed.…”