N. E. Christians and Lukas Dant
Corn gluten meal (CGM) has been screened for efficacy as a natural product herbicide and fertilizer in turf on the same plot since 1991. The study is being conducted at the Iowa State University Research Station north of Ames, IA in an area of 'Parade' Kentucky bluegrass. The soil in this experimental area is a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 4.6% a pH of 6.45, 3 ppm P, and 144 ppm K.
Individual experimental plots are 5 x 5 ft and there are five treatments with three replications. The experimental design is a randomized complete block. Corn gluten meal is applied each year to the same plots at 0, 20, 40, 60, 80, 100, and 120 lbs/1000 ft2 (Table 1). Because corn gluten meal is 10% N, these rates are equivalent to 0, 2, 4, 6, 8, 10, and 12 lb N/1000 ft2. The CGM is applied each year in a single early-spring preemergence application using 'shaker dispensers'. The materials are watered-in with the irrigation system. Supplemental irrigation is used to provide adequate moisture to maintain the grass in good growing condition. In 2002, applications were made on April 26.
Turf quality was monitored from May 7 through October 14 (Table 1). It was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst turf quality.
Weed populations were measured by either counting the number of plants or by estimating the percentage of cover per individual plot. Crabgrass infestations were determined by counting the number of plants per individual plot starting on July 31 (Table 2). Dandelion populations were assessed by counting the number of plants per individual plot (Table 3). Clover populations were determined by estimating the percentage area of each plot covered by clover (Table 4). Dandelion and clover data were taken from May 7 through September 10. Data were analyzed with the Statistical Analysis System (SAS) and the Analysis of Variance (ANOVA) procedure.
Table 1. Visual quality1 of Kentucky bluegrass treated in the 1991 Corn Gluten Meal Weed Control Study.
| Material | lbs CGM/1000 ft2 | lbs N/1000 ft2 | May 9 | May 14 | Jun 1 | Jun 29 | Aug 19 | Sep 10 | Sep 26 | Oct 14 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Untreated control | 0 | 0 | 2 | 2 | 4 | 1 | 6 | 5 | 5 | 5 |
| 2 | Corn gluten meal | 20 | 2 | 4 | 4 | 5 | 2 | 7 | 7 | 6 | 6 |
| 3 | Corn gluten meal | 40 | 4 | 5 | 5 | 6 | 3 | 8 | 8 | 6 | 7 |
| 4 | Corn gluten meal | 60 | 6 | 6 | 5 | 7 | 3 | 8 | 8 | 7 | 7 |
| 5 | Corn gluten meal | 80 | 8 | 6 | 6 | 8 | 6 | 9 | 9 | 8 | 7 |
| 6 | Corn gluten meal | 100 | 10 | 8 | 8 | 8 | 6 | 8 | 8 | 8 | 8 |
| 7 | Corn gluten meal | 120 | 12 | 8 | 8 | 8 | 6 | 9 | 9 | 8 | 8 |
| LSD0.05 | 2.4 | 1.7 | 1.1 | 1.6 | 1.4 | 1.8 | 1.4 | NS | |||
1 Turf quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst turf quality.
NS = means are not significantly different at the 0.05 level.
Table 2. Crabgrass counts1 in Kentucky bluegrass treated in the 1991 Corn Gluten Meal Weed Control Study.
| Material | lbs CGM/1000 ft2 | July 31 | August 19 | Sept 10 | |
|---|---|---|---|---|---|
| 1 | Untreated control | 0 | 0 | 2 | 5 |
| 2 | Corn gluten meal | 20 | 0 | 4 | 3 |
| 3 | Corn gluten meal | 40 | 1 | 0 | 0 |
| 4 | Corn gluten meal | 60 | 0 | 0 | 0 |
| 5 | Corn gluten meal | 80 | 1 | 0 | 0 |
| 6 | Corn gluten meal | 100 | 0 | 2 | 0 |
| 7 | Corn gluten meal | 120 | 0 | 0 | 0 |
| LSD0.05 | NS | NS | NS | ||
1 These values represent the number of crabgrass plants per plot covered.
NS = means are not significantly different at the 0.05 level.
Table 3. Dandelion counts1 in Kentucky bluegrass treated in the 1991 Corn Gluten Meal Weed Control Study.
| Material | lbs CGM/1000 ft2 | May 7 | May 14 | June 1 | June 29 | July 31 | Aug 19 | Sept 10 | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Untreated control | 0 | 25 | 30 | 21 | 56 | 52 | 47 | 45 |
| 2 | Corn gluten meal | 20 | 15 | 17 | 11 | 16 | 19 | 23 | 23 |
| 3 | Corn gluten meal | 40 | 1 | 2 | 1 | 1 | 13 | 3 | 2 |
| 4 | Corn gluten meal | 60 | 0 | 1 | 0 | 1 | 5 | 2 | 1 |
| 5 | Corn gluten meal | 80 | 1 | 0 | 1 | 0 | 11 | 2 | 2 |
| 6 | Corn gluten meal | 100 | 0 | 0 | 0 | 0 | 0 | 2 | 1 |
| 7 | Corn gluten meal | 120 | 0 | 0 | 0 | 0 | 0 | 1 | 1 |
| LSD0.05 | 14.1 | 20.8 | 14.2 | NS | NS | NS | NS | ||
1 These values represent the number of dandelion plants per plot.
Table 4. Percentage clover cover1 in Kentucky bluegrass treated in the 1991 Corn Gluten Meal Weed Control Study.
| Material | lbs CGM/1000 ft2 | May 7 | May 14 | June 1 | June 29 | July 31 | Aug 19 | Sept 10 | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Untreated control | 0 | 31 | 17 | 27 | 22 | 10 | 22 | 30 |
| 2 | Corn gluten meal | 20 | 20 | 20 | 17 | 3 | 3 | 10 | 16 |
| 3 | Corn gluten meal | 40 | 33 | 10 | 10 | 10 | 10 | 15 | 25 |
| 4 | Corn gluten meal | 60 | 27 | 25 | 8 | 5 | 2 | 13 | 22 |
| 5 | Corn gluten meal | 80 | 1 | 2 | 0 | 0 | 13 | 1 | 2 |
| 6 | Corn gluten meal | 100 | 0 | 17 | 0 | 0 | 4 | 1 | 4 |
| 7 | Corn gluten meal | 120 | 0 | 2 | 0 | 0 | 2 | 1 | 2 |
| LSD0.05 | NS | NS | NS | 14.0 | NS | 13.2 | 19.1 | ||
1 These values represent the area per plot covered by clover.
NS = means are not significantly different at the 0.05 level.
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ISU Turfgrass:2003 Turfgrass Report | College of Agriculture |
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