Combining frequent N applications and irrigations for turfgrasses grown in sandy soils is a common occurrence on golf course putting greens. A greenhouse study was conducted to determine leaching losses of nitrate and ammonium nitrogen from `Penncross' creeping bentgrass (Agrostis palustris L.) growing on an 80 sand:20 peat soil mixture following frequent, moderately heavy irrigations and light or moderate N fertilizer applications. Nitrogen sources included calcium nitrate, ammonium nitrate, ammonium sulfate, urea, urea formaldehyde and isobutylediene diurea. Application levels were 9.76 kg N/ha per 7 days and 19.52 kg N/ha per 14 days for 10 weeks. Irrigation equivalent to 38 mm·week-1 was applied in three equal applications. Overall, 46% of the applied water leached. Total leaching losses were <0.5% of the applied N. Nitrate represented the major portion of the leached N, with ammonium losses being negligible. There were no differences between sources when applied at these levels. In a second study, a single 48.8 kg N/ha application resulted in higher leaching losses of N, but only calcium nitrate and ammonium nitrate had total losses > 2% (2.80% and 4.13%, respectively, over an n-day period). Nitrate concentrations were found to exceed 45 mg·liter-1 for ammonium nitrate.
Charles F. Mancino and Joseph Troll
Charles F. Mancino, Dianne Petrunak and Douglas Wilkinson
The loss of fertilizer granules collected in turf clippings during routine putting green mowing has not been determined. The objective of this study was to quantify the amounts of greens-grade granular potassium (K) and nitrogen (N) fertilizers collected during the routine mowing of a `Pennlinks' creeping bentgrass (Agrostis palustris Huds.) putting green. In the first study, five K-containing granular fertilizers were applied at K rates of 2.43 and 4.86 g·m-2. A second study was also performed with six granular Ncontaining fertilizers and one liquid N fertilizer applied at an N rate of 4.86 g·m-2. Both studies were performed twice. Irrigation (6.4 mm) was applied immediately after each fertilizer application and again on the following day. These two irrigations, plus additional irrigation and rain, resulted in each study receiving about 2.54 cm of water over each nineday study period. Mowing and clipping collection using a walk-behind greens mower set to cut at 3.96 mm began two days after treatment (2 DAT) and continued until 9 DAT. The clippings were oven-dried and separated from the fertilizer using a small pneumatic seed cleaner. Collected fertilizer was weighed and expressed as a percentage of the fertilizer applied. Liquid N fertilizer loss was estimated to be the difference between clipping N content of treated plots and untreated controls. Total K fertilizer loss was: UHS Signature 15-0-30 (15.3% to 22.9%) > Lebanon Isotek 11-3-22 (8.7% to 10.7%) > Scott's Contec 13-2-26 (4.9% to 7.4%) > Lesco Matrix 12-0-22 (0.1% to 0.4%) = Lesco Matrix 5-0-28 (0.1% to 0.5%). Signature was the only fertilizer significantly affected by rate and a greater percentage of loss occurred at the lower K application rate. Most loss occurred during the first and second mowing events with small amounts of fertilizer found in clippings from later mowings. The two Lesco materials were not found in clippings after the first mowing. Nitrogen fertilizer granule loss was also greatest with the first and second mowings. Total percentage of losses were IBDU 31-0-0 (75.4%) > Polyon 41-0-0 (70.8%)> Milorganite 6-2-0 (55.7%) > Nutralene 40-0-0 (47.0%) > UHS Signature (19.3%) > Isotek 11-3-22 (9.5%) > N-Sure Pro 30-0-0 (1.9%). In both studies, fertilizer loss appeared to be most related to water-solubility of the fertilizer, but size and density might also be factors.