The experimental design is a randomized complete block design. Individual experimental plots are 10 x 10 ft with three replications. 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 2001 were made on April 26 before crabgrass germination. It was 80º F and sunny with a slight wind. The second application of treatment 2 was made on June 25 under cloudy skies with a high temperature of 83º and a slight S wind. The third application of treatment 2 and the second of treatments 3 and 4 were made on August 6. It was 86º and sunny with a 10 mph wind from the south. 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 12. It was 75 deg and sunny with a southerly wind at 15-20 mph. Temperatures remained above normal for the entire spring and summer 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 May 8 through September 13. 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 12 but because of the hot temperatures and low rainfall, the growth rate was very slow. Population assessments could not be made until July 27. Subsequent data were recorded on August 9, August 16, August 28, and September 13 (Table 2).

Broadleaf data were taken from May 8 through September 13. Dandelion and clover were the predominate broadleaf weed species within the experimental plot. Dandelion populations were measured by counting the number of plants per plot (Tables 4). Clover infestations were estimated by determining the percentage area in each individual plot covered by clover (Tables 6).

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 (Table 3, 5, and 7).

The 2001 growing season was hot and 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 of bluegrass treated with CGM was better than the untreated controls.

Crabgrass populations were reduced by CGM at all application rates as compared with the untreated controls (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 and the untreated control. Mean reductions in crabgrass counts were > 94% in turf treated with 2 applications of 20 lb CGM or 30 lb followed by 10 lb CGM as compared with the untreated control (Table 3).

The level of crabgrass control was lower at 10 lb CGM (four applications) than in 2001 (Tables 8 and 9). Split applications of 20 lb CGM provided 100% crabgrass reductions in 2001 and 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 94% in 2001.

Dandelion numbers were significantly lower in all CGM treated turf as compared with the untreated controls for the entire 2001 season (Table 4). The best dandelion control was in turf treated with split applications of 20 lb CGM but this level was not different from the other CGM treatments. Dandelion reductions were similar for all CGM treatments and ranged from mean reductions ranged from 72.5 to 83.4% (Table 5).

Dandelion control was slightly lower in 2001 than in 2000 (Table 10). Split applications of 20 lb CGM provided 83% control in 2001 but the level was 85 and 88% in 1999 and 2000, respectively.

Clover cover was significantly lower throughout the season in all CGM treated bluegrass as compared with the untreated controls. Clover populations were significantly lower in all CGM treated turf than in untreated on all data collection dates (Table 6). Mean reductions for all CGM treatments were > 91% and all were statistically different from the untreated controls (Table 7).

Clover control in 2001 was approximately equal to the level of control recorded in 2000 and 1999 (Table 11). At all CGM treatment levels, clover populations were lower than in treated bluegrass for 1996 through 1998.

Table 1. Turf quality¹ of Kentucky bluegrass treated with corn gluten meal for the 1995 Corn Gluten Meal Rate Weed Control Study.