N. E. Christians and Lukas Dant
Corn gluten meal (CGM) is being screened for efficacy as a natural product herbicide in turf. This long-term study began in 1995 at the Iowa State University Horticulture Research Station north of Ames, IA. The experimental plot is in established 'Ram 1' Kentucky bluegrass. The soil is a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 4.8%, a pH of 7.1, 6 ppm P, and 170 ppm K. Prior to treatment in 1995, the percentage broadleaf weed cover within the study perimeter exceeded 50%.
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 application of 10 lb/1000 ft2, and a single application of 40 lb/1000 ft2 are included with an untreated control.
Initial applications in 2002 were made on April 26 before crabgrass germination. The second application of treatment 2 was made on June 2. The third application of treatment 2 and the second of treatments 3 and 4 were made on July 18. The final application of treatment 2 was made on August 14.
The experimental plot was checked for phytotoxicity after each treatment. Turf quality data were taken weekly from spring greenup on May 8 through October 14. Visual quality was measured using a 9 to 1 scale with 9 = best and 6 = lowest acceptable, and 1 = worst quality (Table 1).
Broadleaf data were taken from May 8 through September 10. 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 (Table 3). Clover infestations were estimated by determining the percentage area in each individual plot covered by clover (Table 4). Data were analyzed with the Statistical Analysis System (SAS) and the Analysis of Variance (ANOVA) procedure.
Table 1. Turf quality1 of Kentucky bluegrass treated with corn gluten meal for the 1995 Corn Gluten Meal Rate Weed Control Study.
| Material | Rate lb product/1000 ft2 | May 9 | May 14 | Jun 2 | Jun 29 | Aug 19 | Sep 26 | Oct 14 | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Untreated control | NA | 4 | 2 | 6 | 1 | 6 | 4 | 7 |
| 2 | Corn gluten meal | 10 fb 10 fb 10 fb 10 | 7 | 7 | 7 | 3 | 8 | 7 | 8 |
| 3 | Corn gluten meal | 20 fb 20 | 6 | 7 | 7 | 2 | 8 | 7 | 8 |
| 4 | Corn gluten meal | 30 fb 10 | 7 | 7 | 7 | 3 | 8 | 7 | 8 |
| 5 | Corn gluten meal | 40 | 7 | 6 | 6 | 3 | 7 | 6 | 7 |
| LSD0.05 | 1.9 | 1.3 | NS | NS | NS | 1.7 | NS | ||
Table 2. Crabgrass counts1 in Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study.
| Material | Rate lb product/1000 ft2 | July 31 | August 19 | Sept 10 | |
|---|---|---|---|---|---|
| 1 | Untreated control | NA | 17 | 16 | 14 |
| 2 | Corn gluten meal | 10 fb 10 fb 10 fb 10 | 5 | 4 | 2 |
| 3 | Corn gluten meal | 20 fb 20 | 6 | 4 | 3 |
| 4 | Corn gluten meal | 30 fb 10 | 4 | 4 | 3 |
| 5 | Corn gluten meal | 40 | 9 | 11 | 8 |
| LSD0.05 | NS | NS | NS | ||
1 These values represent the number of crabgrass plants per plot.
NS = means are not significantly different at the 0.05 level.
Table 3. Dandelion counts1 in Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study.
| Material | Rate lb product/1000 ft2 | May 7 | May 14 | Jun 2 | Jun 29 | Jul 31 | Aug 19 | Sep 10 | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Untreated control | NA | 37 | 32 | 19 | 27 | 81 | 58 | 58 |
| 2 | Corn gluten meal | 10 fb 10 fb 10 fb 10 | 18 | 8 | 4 | 7 | 23 | 24 | 15 |
| 3 | Corn gluten meal | 20 fb 20 | 19 | 6 | 7 | 11 | 21 | 24 | 17 |
| 4 | Corn gluten meal | 30 fb 10 | 17 | 6 | 3 | 7 | 27 | 26 | 18 |
| 5 | Corn gluten meal | 40 | 21 | 9 | 10 | 10 | 33 | 31 | 26 |
| LSD0.05 | NS | NS | NS | NS | 33.5 | NS | NS | ||
1 These data represent the number of dandelion plants per plot.
Table 4. Percentage clover cover1 in Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study.
| Material | Rate lb product/1000 ft2 | May 7 | May 14 | Jun 2 | Jun 29 | Jul 31 | Aug 19 | Sep 10 | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Untreated control | NA | 65 | 53 | 22 | 57 | 60 | 58 | 42 |
| 2 | Corn gluten meal | 10 fb 10 fb 10 fb 10 | 1 | 0 | 0 | 0 | 4 | 5 | 4 |
| 3 | Corn gluten meal | 20 fb 20 | 0 | 1 | 3 | 0 | 3 | 5 | 5 |
| 4 | Corn gluten meal | 30 fb 10 | 2 | 2 | 5 | 1 | 8 | 10 | 17 |
| 5 | Corn gluten meal | 40 | 2 | 2 | 8 | 0 | 7 | 8 | 7 |
| LSD0.05 | 40.9 | 26.5 | NS | 40.5 | 32.1 | 21.4 | NS | ||
1 These figures represent the percentage of each plot covered by clover.
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ISU Turfgrass:2003 Turfgrass Report | College of Agriculture |
Contents ©1995-2003, ISU Horticulture Department