Individual experimental plots are 10 x 10 ft with three replications. The experimental design is a randomized complete block design. Each year corn gluten meal is applied to the same plots at a yearly rate of 40 lb CGM/1000 ft² (equivalent to 4 lb N/1000 ft²) using four different regimes of single and split applications for a total of five treatments (Table 1). Four applications of 10 lb/1000 ft², split applications of 20 lb/1000 ft², an initial application of 30 lb plus a sequential of 10 lb/1000 ft², and a single application of 40 lb/1000 ft² are included with an untreated control.

Initial applications for 2000 were made on April 18 before crabgrass germination. It was warm (65º) and sunny with a SW wind and the temperatures remained warm with only 0.13" rainfall for the remainder of April. The second application of treatment 2 was made on June 19 under sunny skies with a high temperature of 83º and a SW wind. The third application of treatment 2 and the second of treatments 3 and 4 were made on July 27. It was 86º, sunny and dry. There was no rain until August 4 and only 2.43" of rainfall for the entire month of August. The final application of treatment 2 was made on September 5. Temperatures remained above normal for the entire month of September and rainfall amounts were below normal.

The experimental plot was checked for phytotoxicity after each treatment. Turf quality data were taken weekly from spring greenup on April 26 through September 12. Visual quality was measured using a 9 to 1 scale with 9 = best and 6 = lowest acceptable, and 1 = worst quality (Table 1).

Crabgrass was first observed on June 27. Population data were recorded on July 14, July 25, August 2, August 8, August 16, August 24, August 29 and September 12 (Tables 2 and 3).

Broadleaf data were taken from April 26 through September 12. Dandelion and clover were the predominate broadleaf weed species within the experimental plot. Dandelion populations were measured counting the number of plants per plot Tables 4 and 5). Clover infestations were estimated by determining the percentage area in each individual plot covered by clover (Tables 6 and 7).

Data were analyzed with the Statistical Analysis System (SAS, Version 6.12) and the Analysis of Variance (ANOVA) procedure. Means comparisons were made with Fisher’s Least Significant Difference test (LSD). Crabgrass, clover, and dandelion population data were converted to percentage reductions as compared with the untreated controls (Tables 3, 5, and 7).

The 2000 growing season was extremely dry. As a result there was less response to the nitrogen in the corn gluten meal than in previous years. Supplemental irrigation was used as required to keep the bluegrass from entering dormancy. In spite of the growing conditions, turf quality was significantly better in bluegrass treated with CGM than in the untreated control for most of the season (Table 1). By September 5, the turf was dormant but rainfall in late October resulted in significant greening so additional data were taken on October 27. On this date, turfgrass that received sequential applications (treatments 2, 3, and 4) had better quality than the untreated control and treated turf that received only an initial CGM treatment. Mean visual quality for the entire season was better for bluegrass treated with CGM than the untreated grass.

Crabgrass populations were statistically reduced by CGM at all application rates as compared with the untreated control from August 2 through September 12 (Table 2). The best crabgrass control was in turf treated with split applications of 20 lb CGM but this level of control was not statistically different from the other CGM treatments. Mean reductions in crabgrass counts were > 85% in all CGM treated turf as compared with the untreated control (Table 3).

In 2000, crabgrass counts in CGM treated turf were statistically lower than in the untreated control (Table 8). Crabgrass control was better at all CGM treatment levels than in previous years. Four sequential applications of 10 lb CGM provided 85% reduction in crabgrass counts in 2000 but only 28, 0, 48, 42, and 67% in 1995, 1996, 1997, 1998, and 1999, respectively. Split applications of 20 lb CGM provided 100% crabgrass reductions in 2000 as compared to 45, 33, 50, 86, and 95% in 1995, 1996, 1997, 1998, and 1999, respectively. A single 40 lb CGM application decreased crabgrass counts by 92% in 2000.

Dandelion numbers were significantly lower in all CGM treated turf as compared with the untreated controls for the entire 2000 season (Table 4). The highest level of dandelion control (88.4% reduction) was in turf treated with split applications of 20 lb CGM but this control was not different from the other CGM treatments. Mean crabgrass reductions were similar for all CGM treatments and ranged from 77.8 to 88.4% (Table 5). Dandelion control was equal to or slightly better than control in previous years (Table 10). Dandelion reductions were 48, 50, 66, and 69% in 1996, 1997, 1998, and 1999, respectively as compared with 78% in 2000.

Clover cover fluctuated throughout the season because of the dry conditions. Clover populations were significantly lower in all CGM treated turf than in untreated on all data collection dates except May 2 and June 2 (Table 6). Mean reductions for all CGM treatments were > 94% and all were statistically different from the untreated controls (Table 7). Clover control in 2000 was approximately equal to control in 1999. At all CGM treatment levels, control was better than control in 1996, 1997 and 1998 (Table 11).

Table 1. Visual quality¹ of Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study (April 26 - October 27).