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 (EEF) 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 could be classified as an enhanced efficiency fertilizer. To determine this, the objectives were: a) to determine if incorporating humic substances will increase the plant-available N collected on ion exchange membranes (IEM) over a growing season and b) 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 humic-coated 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 with 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 with 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.

中文翻译：

---

腐殖质施肥的肯塔基兰草的植物有效土壤氮通量和草坪质量

高质量的草坪草需要足量的氮 (N) 肥料。然而，过量施氮会通过浸出和气体排放增加氮损失。增效肥料 (EEF) 和腐殖质已被用于减少氮向环境的流失。在带有肯塔基兰草 ( Poa pratensis)的原生土壤上进行了为期两年的田间试验L.) 调查向肥料中添加腐殖质是否可以归类为增效肥料。为确定这一点，目标是：a) 确定掺入腐殖质是否会增加在整个生长季节在离子交换膜 (IEM) 上收集的植物可用氮，以及 b) 确定肥料的氮释放 (NR) 曲线使用网袋技术进行治疗。肥料处理包括腐殖质涂层尿素 (HCU)、多涂层腐殖质涂层尿素 (PCHCU)、尿素 + 腐殖质分散颗粒 (HDG)、多涂层硫涂层尿素 (PCSCU)、稳定氮、尿素和未处理的控制。总的来说，与单独使用肥料相比，向肥料中添加腐殖质并没有改善草坪草的质量。此外，与未经处理的对照相比，所有肥料处理都改善了草坪质量，并且在几乎整个生长季节都提供了可接受的草坪质量。在生长季节，与所有其他处理相比，PCHCU 在 IEM 上捕获的无机 N 多 25%。PCHCU 和 PCSCU 都显示出延长的 NR 曲线，其中 PCHCU 具有更长的释放期。总之，PCHCU 增加了植物可利用的 N 浓度，缓慢释放，应归类为 EEF。