Abstract

As new fertilizer materials become available for turfgrass fertilization, their relative merits should be evaluated under various field conditions so that sound recommendations can be made concerning their use. In this study on ‘Pennpar’ creeping bentgrass (Agrostis palustris Huds.), single applications of four slow-release N fertilizers and multiple applications of urea applied to fine, mixed, mesic Typic Hapludalf soil were compared for four consecutive growing seasons. Split applications of slow-release materials were also included in the fourth season. Clipping yields and turf color were used to evaluate response to fertilization. Growth patterns varied from year to year, but certain relationships between treatments generally remained the same: 1) greatest initial response occurred with IBDU (isobutylidene diurea); 2) yields from slow-release treatments equalled or exceeded those from the urea treatment for 13 to 14 weeks, thereafter urea gave higher yields; 3) response from sulfur-coated urea (21% 7-day dissolution rate) and resin-coated fertilizer (Agriform CRF 19-3-11) was intermediate between IBDU and ureaform (Uramite). Split applications of slow-release sources reduced the flush of spring growth and increased turf color in the fall to an acceptable level. Color was unacceptable in the fall when single spring applications were used. The delay in response noted after IBDU applications on Kentucky bluegrass (Poa pratensis L.) in other experiments was not as apparent under the conditions of this study, possibly due to the incorporation of fertilizer by aerating and topdressing at the time of application and more liberal watering on the bentgrass area.

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