This study was designed to screen new Sustane formulations on Kentucky bluegrass. The trial was conducted at the Iowa State University Horticulture Research Station in established 'Park' Kentucky bluegrass. The soil in this area was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic content of 4.0, a pH of 7.1, 8 ppm P, and 81 ppm K. The experimental design was a randomized complete block with three replications. Individual plot size was 5 x 5 ft with 3 ft barrier rows between replications.

Four medium grade Sustane formulations were provided. Sustane 5-2-4 + Fe, Sustane 18-1-8 + Fe (with Nutralene & PCSCU), Sustane 10-1-2 (all organic), and Sustane + Novex 12-2-12 experimental were screened with corn gluten meal and an untreated control. All materials were applied at a yearly rate of 2 lb N/1000 ft² in split applications of 1 lb N/1000 ft² on May 22 and August 2, 2000. The fertilizers were applied using cardboard cartons as 'shaker dispensers' to ensure uniform application and were watered in.

The study was monitored weekly for visual quality from June 2 through September 12 (Table 1). Rainfall in October caused a 'greenup' so additional quality data were taken on October 27. Quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable and 1 = worst quality.

Fresh clipping weight data were taken from June 2 through September 12 (Table 2). Because of the extremely dry season, modifications were made so data were taken when sufficient growth had occurred.

Data were analyzed using the Statistical Analysis System (SAS Institute Inc., 1989-1996) and the Analysis of Variance (ANOVA) procedure. Treatment effects on fresh clipping weight and visual quality were tested using Fisher's Least Significant Difference (LSD) test.

There were significant differences in turf quality from June 2 through June 30 (Table 1). During this period, however, some fertilizers did not produce better quality than the untreated control. Between July 7 and August 2 quality was similar for treated and untreated turf. Following the sequential applications on August 2, the quality of the treated turf improved. The quality of turf treated with the all natural fertilizers, Sustane 10-1-2 and corn gluten meal, did not improve as rapidly as turf treated with the other fertilizers. Data from the late 'greenup' in October show that all fertilizers improved quality as compared with the untreated control. The best quality according to the mean data was for turf treated with Sustane 18-1-8 + Fe (with Nutralene & PCSCU).

Fresh clipping weights were similar for treated and untreated turf from June 2 through August 2 (Table 2). On August 16, turf treated with either Sustane 5-2-4 + Fe, Sustane 18-1-8 + Fe (with Nutralene & PCSCU), or Sustane + Novex 12-2-12 had significantly more clippings than the untreated control. On August 29 and September 12, Sustane 18-1-8 + Fe (with Nutralene & PCSCU) and corn gluten meal produced the most clippings.

Table 1. Turf quality¹ of 'Park' Kentucky bluegrass treated for the 2000 Sustane Kentucky Bluegrass Fertility Trial.