Corn gluten meal (CGM) is being screened for efficacy as a natural product herbicide in turf in this long-term study begun in 1995. It is being conducted at the Iowa State University Horticulture Research Station north of Ames, IA in established 'Ram 1' Kentucky bluegrass. The soil is a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.8%, a pH of 7.1, 4 ppm P, and 96.5 ppm K. The initial broadleaf weed population exceeded 50% cover on most of the test area.
Individual experimental plots are 10 x 10 ft with 4 treatments and 3 replications. The experimental design is a randomized complete block. Each year corn gluten meal is applied at a yearly rate of 40 lb. CGM/1000 ft2 (equivalent to 4 lb. N/1000 ft2) using 4 different regimes of single and split applications (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 1998 were made on April 21 before crabgrass germination. The second application of treatment 2 was made on June 3, the third on July 14, and the final on August 26. Sequential applications of treatments 3 and 4 were made on July 14.
The experimental plot was checked for phytotoxicity after each treatment. The study was monitored for visual quality throughout the season. Visual quality was measured using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality (Tables 1 and 2). Visual quality data were taken on April 22, May 13, May 18, May 27, June 10, June 18, June 30, July 9, July 15, July 24, July 29, August 11, August 18, and August 26.
Populations of annual grass and perennial broadleaf weed species were surveyed. Crabgrass populations were assessed by counting the number of plants per individual plot on July 9, July 24, July 29, August 11, August 18, and August 26 (Table 3). Clover infestations were estimated by determining the percentage of area in each individual plot covered by clover. These data were taken on July 29, August 11, August 18, and August 26 (Table 5). Dandelion populations were measured by counting the number of plants per plot on July 29, August 11, August 18, and August 26 (Table 7). Levels of crabgrass, clover, and dandelion control were expressed by converting the population data to reductions as compared with the untreated control (Table 4, 6, and 8).
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).
There were no phytotoxic symptoms detected on the treated bluegrass. Visual turf quality was significantly better in bluegrass treated with CGM than in the untreated control on May 13, May 27, June 10, June 18, June 30, July 9, August 11, August 18, and August 26 (Table 1 and 2). Mean visual quality for the entire season was better for bluegrass treated with CGM than the untreated grass.
Crabgrass populations were lower in turf treated with CGM than in untreated turf but the counts were not statistically different (Table 3). Crabgrass numbers were low in the untreated controls. Broadleaf weed species were well established when the crabgrass was emerging especially in the untreated controls and the competition from the broadleaves and the mature turf probably prevented the establishment of large crabgrass populations within the untreated plots. Reductions in crabgrass populations were not significant for any of the CGM treatments on any of the collection dates but there were large numerical reductions achieved in treated bluegrass as compared with untreated turf (Table 4). Bluegrass treated with split applications of 20 lb. CGM reduced crabgrass counts by > 89% from July 9 through August 11.
In 1998, crabgrass control was much better overall than in 1995, 1996, and 1997 (Table 9). In contrast to 1996 and 1997, there was more crabgrass in the untreated controls than in treated grass in 1998. Split applications of 20 lb. CGM provided 86% crabgrass reductions in 1998 as compared to 45, 33, and 50% in 1995, 1996, and 1997, respectively.
There was significantly less clover in CGM treated turf than in the untreated controls on all data collection dates except August 18 (Table 5). All CGM rates significantly decreased clover populations and clover cover was lowest in turf treated with a single application of 40 lb. CGM. The mean clover cover in untreated turf was 40.4% as compared to 10.7, 11.4, 14.7, and 3.0% cover in turf receiving treatments 2, 3, 4, and 5, respectively. The single application of 40 lb. CGM provided Ñ 89% reductions in clover cover throughout the season as compared to the untreated control (Table 6).
Clover control was better in 1998 than 1996 and 1997 in turf treated with CGM four times at 10 lb. (Table 10). Clover control in 1998 with split applications of 20 lb. was slightly less than in 1997 and similar to 1996. Control provided by CGM at 30 lb. followed by 10 lb. was much lower in 1998 as compared with 1996 and 1997. A single application at 40 lb. provided similar clover cover reductions in 1998 as in 1996 and slightly lower than 1997.
Dandelion cover was significantly less in all CGM treated turf as compared to the untreated control on all data collection days except August 26 (Table 7). Percentage reductions in dandelion cover were similar for all CGM treatments (Table 8).
In 1998, dandelion control was higher than in 1996 and 1997 when CGM was applied four times at 10 lb. and in a single application at 40 lb. (Table 11). Dandelion reductions were similar in 1996, 1997, and 1998 for CGM at 20 lb. split applications. Percentage reductions were much higher in 1998 as compared with 1996 and 1997 for CGM applied at 30 lb. followed by 10 lb.
Table 1. Visual quality1 of Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study (April 22 - June 30).
|
|
Material |
Rate (lb. product /1000 ft2) |
22 |
13 |
18 |
27 |
10 |
18 |
30 |
|
|
Untreated control |
|
|
|
|
|
|
|
|
|
|
Corn gluten meal |
10 fb 10 |
|
|
|
|
|
|
|
|
|
Corn gluten meal |
|
|
|
|
|
|
|
|
|
|
Corn gluten meal |
|
|
|
|
|
|
|
|
|
|
Corn gluten meal |
|
|
|
|
|
|
|
|
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
1Visual quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst turf quality.
All treatments were at an annual rate of 4 lb.s N/1000 ft2. Initial applications were made on April 21. Second application of trt 2 was made on June 3, the third on July 14, and the final on August 26. Sequential applications of trt 3 & 4 were made on July 14.
NS = means are not significantly different at the 0.05 level
Table 2. Visual quality1 of Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study (July 9 - August 26).
|
|
Material |
Rate (lb. product /1000 ft2) |
9 |
15 |
24 |
29 |
11 |
18 |
26 |
|
|
|
Untreated control |
|
|
|
|
|
|
|
|
|
|
|
Corn gluten meal |
10 fb 10 |
|
|
|
|
|
|
|
|
|
|
Corn gluten meal |
|
|
|
|
|
|
|
|
|
|
|
Corn gluten meal |
|
|
|
|
|
|
|
|
|
|
|
Corn gluten meal |
|
|
|
|
|
|
|
|
|
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
|
1Visual 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 3. Crabgrass counts per plot1 in Kentucky bluegrass treated with corn gluten meal (CGM) in the 1995 Corn Gluten Meal Rate Weed Control Study.
|
26 |
|
|
|
|
|
|
|
|
|
|||||||
|
|
Untreated control |
|
8.7 |
13.3 |
16.7 |
18.3 |
23.3 |
31.7 |
18.7 |
|||||||
|
|
Corn gluten meal |
|
3.3 |
9.0 |
6.7 |
11.7 |
11.7 |
23.3 |
10.9 |
|||||||
|
|
Corn gluten meal |
|
0.3 |
0.7 |
1.7 |
2.0 |
3.7 |
7.0 |
2.6 |
|||||||
|
|
Corn gluten meal |
|
1.0 |
2.3 |
2.0 |
7.0 |
5.3 |
7.3 |
4.2 |
|||||||
|
|
Corn gluten meal |
|
5.0 |
8.3 |
6.7 |
10.0 |
6.7 |
16.7 |
8.9 |
|||||||
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
|||||||
1These values represent the number of crabgrass plants per plot.
NS = means are not significantly different at the 0.05 level.
Table 4. Crabgrass count reductions1 in Kentucky bluegrass treated with corn gluten meal (CGM) in the 1995 Corn Gluten Meal Rate Weed Control Study.
|
|
|
(lb. product /1000 ft2) |
9 |
24 |
29 |
11 |
18 |
26 |
|
|
|
|
|
|
||||||
|
|
Untreated control |
|
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
|
Corn gluten meal |
|
61.7 |
32.3 |
60.1 |
36.2 |
50.0 |
26.4 |
41.5 |
|
|
Corn gluten meal |
|
96.2 |
95.0 |
90.0 |
89.1 |
84.3 |
77.9 |
86.3 |
|
|
Corn gluten meal |
|
88.5 |
82.5 |
88.0 |
61.7 |
77.1 |
76.9 |
77.7 |
|
|
Corn gluten meal |
|
42.5 |
37.3 |
60.1 |
45.4 |
71.4 |
47.4 |
52.5 |
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
1These values represent the percentage reduction in crabgrass plants per plot as compared with the untreated controls.
All treatments were at an annual rate of 4 lb.s N/1000 ft2. Initial applications were made on April 21. Second application of trt 2 was made on June 3, the third on July 14, and the final on August 26. Sequential applications of trt 3 & 4 were made on July 14.
NS = means are not significantly different at the 0.05 level.
Table 5. Percentage clover cover per plot1 in Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study.
|
|
|
(lb. product/1000 ft2) |
29 |
11 |
18 |
26 |
|
|
|
|
|
|
||||
|
|
Untreated control |
|
40.0 |
41.7 |
31.7 |
48.3 |
40.4 |
|
|
Corn gluten meal |
|
10.7 |
8.3 |
7.0 |
16.7 |
10.7 |
|
|
Corn gluten meal |
|
10.0 |
12.0 |
6.7 |
17.0 |
11.4 |
|
|
Corn gluten meal |
|
11.7 |
16.0 |
14.3 |
16.7 |
14.7 |
|
|
Corn gluten meal |
|
1.7 |
1.7 |
3.3 |
5.3 |
3.0 |
|
|
LSD0.05 |
|
|
|
|
|
|
1These data represent the area per plot covered by clover.
NS = means are not significantly different at the 0.05 level.
Table 6. Percentage clover cover reductions1 in Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study.
|
|
|
(lb. product/1000 ft2) |
29 |
11 |
18 |
26 |
|
|
|
|
|
|
||||
|
|
Untreated control |
|
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
|
Corn gluten meal |
|
73.3 |
80.0 |
77.9 |
65.5 |
73.6 |
|
|
Corn gluten meal |
|
75.0 |
71.2 |
79.0 |
64.8 |
71.7 |
|
|
Corn gluten meal |
|
70.8 |
61.6 |
54.8 |
65.5 |
63.7 |
|
|
Corn gluten meal |
|
95.8 |
96.0 |
89.5 |
89.0 |
92.6 |
|
|
LSD0.05 |
|
51.3 |
39.6 |
|
44.4 |
48.5 |
1These values represent the percentage reductions in clover cover per plot as compared with the untreated control.
NS = means are not significantly different at the 0.05 level.
Table 7. Percentage dandelion cover1 in Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study.
|
|
|
(lb. product/1000 ft2) |
29 |
11 |
18 |
26 |
|
|
|
|
|
|
||||
|
|
Untreated control |
|
25.0 |
20.0 |
15.0 |
28.3 |
22.1 |
|
|
Corn gluten meal |
|
8.3 |
5.0 |
5.0 |
11.7 |
7.5 |
|
|
Corn gluten meal |
|
10.0 |
6.7 |
6.7 |
13.3 |
9.2 |
|
|
Corn gluten meal |
|
6.7 |
6.0 |
4.3 |
10.0 |
6.8 |
|
|
Corn gluten meal |
|
10.0 |
6.7 |
5.7 |
11.7 |
8.5 |
|
|
LSD0.05 |
|
7.1 |
6.6 |
4.6 |
|
4.7 |
1These figures represent the area per plot covered by dandelions.
All treatments were at an annual rate of 4 lb.s N/1000 ft2. Initial applications were made on April 21. Second application of trt 2 was made on June 3, the third on July 14, and the final on August 26. Sequential applications of trt 3 & 4 were made on July 14.
NS = means are not significantly different at the 0.05 level.
Table 8. Percentage reductions in dandelion cover1 in Kentucky bluegrass treated with corn gluten meal in the 1995 Corn Gluten Meal Rate Weed Control Study.
|
|
|
(lb. product/1000 ft2) |
29 |
11 |
18 |
26 |
|
|
|
|
|
|
||||
|
|
Untreated control |
|
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
|
Corn gluten meal |
|
66.7 |
75.0 |
66.7 |
58.8 |
66.1 |
|
|
Corn gluten meal |
|
60.0 |
66.7 |
55.6 |
52.9 |
58.5 |
|
|
Corn gluten meal |
|
73.3 |
70.0 |
71.1 |
64.7 |
69.5 |
|
|
Corn gluten meal |
|
60.0 |
66.7 |
62.2 |
58.8 |
61.5 |
|
|
LSD0.05 |
|
28.3 |
33.1 |
31.0 |
|
21.2 |
1These figures represent the percentage reductions in dandelion cover per plot as compared to the untreated control.
All treatments were at an annual rate of 4 lb.s N/1000 ft2. Initial applications were made on April 21. Second application of trt 2 was made on June 3, the third on July 14, and the final on August 26. Sequential applications of trt 3 & 4 were made on July 14.
NS = means are not significantly different at the 0.05 level.
Table 9. Crabgrass counts per plot1 and percentage crabgrass reductions2 in Kentucky bluegrass treated in the 1995 Corn Gluten Meal Rate Weed Control Study for 1995 through 1998.
|
|
|
|
|
|
|
|
|
|
|
||||||
|
|
|
(lb. product /1000 ft2) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||||||
|
|
Untreated control |
|
0 |
|
|
|
0 |
|
|
|
0 |
|
19 |
|
0 |
|
|
Corn gluten meal |
fb 10 fb 10 |
28 |
|
|
|
0 |
|
|
|
48 |
|
11 |
|
42 |
|
|
Corn gluten meal |
|
45 |
|
|
|
33 |
|
|
|
50 |
|
3 |
|
86 |
|
|
Corn gluten meal |
|
44 |
|
|
|
67 |
|
|
|
61 |
|
4 |
|
78 |
|
|
Corn gluten meal |
|
54 |
|
|
|
0 |
|
|
|
0 |
|
9 |
|
53 |
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1Crabgrass counts represent the number of crabgrass plants per plot.
2These values represent the percentage reduction in plants per plot as compared with the untreated controls.
NS = means are not significantly different at the 0.05 level.
Table 10. Percentage clover cover per plot1 and percentage clover cover reductions2 in Kentucky bluegrass treated in the 1995 Corn Gluten Meal
Rate Weed Control Study for 1996 through 1998.
|
|
|
|
|
|
|
|
|
|
||||||
|
|
|
(lb. product /1000 ft2) |
|
clover cover1 |
|
|
|
clover cover1 |
|
clover reduction2 |
|
clover cover1 |
|
|
|
|
|
|
|
|
|
|
|
|
||||||
|
|
Untreated control |
|
|
20 |
|
0 |
|
40 |
|
0 |
|
40 |
|
0 |
|
|
Corn gluten meal |
fb 10 fb 10 |
|
11 |
|
45 |
|
14 |
|
65 |
|
11 |
|
74 |
|
|
Corn gluten meal |
|
|
6 |
|
69 |
|
7 |
|
82 |
|
11 |
|
72 |
|
|
Corn gluten meal |
|
|
3 |
|
90 |
|
7 |
|
92 |
|
15 |
|
64 |
|
|
Corn gluten meal |
|
|
2 |
|
92 |
|
3 |
|
83 |
|
3 |
|
93 |
|
|
LSD0.05 |
|
|
|
|
|
|
22 |
|
58 |
|
20 |
|
49 |
1These values represent the area per plot covered by clover.
2These values represent the percentage reductions in clover cover per plot as compared with the untreated control.
NS = means are not significantly different at the 0.05 level
Table 11. Percentage dandelion cover per plot1 and percentage dandelion cover reductions2 in Kentucky bluegrass treated in the 1995 Corn Gluten
Meal Rate Weed Control Study for 1996 through 1998.
|
|
|
|
|
|
|
|
|
|
||||||
|
|
|
(lb. product /1000 ft2) |
|
dandelion cover1 |
|
|
|
dandelion cover1 |
|
|
|
dandelion cover1 |
|
|
|
|
|
|
|
|
|
|
|
|
||||||
|
|
Untreated control |
|
|
|
|
0 |
|
17 |
|
0 |
|
22 |
|
0 |
|
|
Corn gluten meal |
fb 10 fb 10 |
|
|
|
48 |
|
8 |
|
50 |
|
8 |
|
66 |
|
|
Corn gluten meal |
|
|
|
|
50 |
|
7 |
|
60 |
|
9 |
|
59 |
|
|
Corn gluten meal |
|
|
|
|
28 |
|
12 |
|
28 |
|
7 |
|
69 |
|
|
Corn gluten meal |
|
|
|
|
50 |
|
7 |
|
58 |
|
9 |
|
62 |
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
|
|
5 |
|
21 |
1Percentage dandelion cover data represent the area per plot covered by dandelions.
2These values represent the percentage reductions in dandelion cover per plot as compared with the untreated control.
NS = means are not significantly
different at the 0.05 level
 |
ISU Horticulture:Publications:1999 Turfgrass Report | College of Agriculture |