Field-Scale Measurement of Ammonia Volatilization From Turfgrass Fertilizers.

Ammonia volatilization from fertilized turfgrass can be an issue of concern, especially if irrigation is not available, and if urea-based N sources are used. The objective of this work was to quantify ammonia loss from fertilized turfgrass as affected by N source. The 10 week experiment took place in 2009 and 2010 on a mixed sward of bermudagrass (Cynodon dactylon Pers.) and bahiagrass (Paspalum notatum) maintained at a mowing height of 6.4 cm. There were four fertilizer treatments for the experiments, each replicated three times. An unfertilized background control plot was also included. Treatments were the N fertilizer sources urea (46-0-0), polymer coated urea (42-0-0), UMaxx (47-0-0), and XCU (43-0-0). Fertilizers were applied at 7.3 g m-2 in July of 2009 and 2010, with no irrigation. Ammonia was captured from 45-m diameter circular plots using a passive micrometeorological system, which uses a three meter high rotating mast was placed in the center of the plot. Five NH3 collection tubes were inserted perpendicular to the mast at 5 heights along the mast: 40, 70, 150, 220, and 300 cm above the soil surface. Tubes were collected once a week for 10 weeks, and ammonium extracted from each tube, and analyzed colorimetrically. Without irrigation to incorporate the urea, NH3 loss from that source was substantial, and averaged 25% of N applied. Ammonia loss from the other sources typically averaged around 10% of N applied. Regardless of N source, greatest NH3 volatilization occurred in the first week after application.