1999 Corn Gluten Meal/Urea Crabgrass Control Study - Year 2
Barbara R. Bingaman and Nick E. Christians
This study was initiated in 1999 to determine if the levels of annual grass and broadleaf weed control provided by corn gluten meal (CGM) treatments can be explained by the nitrogen response of treated bluegrass and not herbicidal activity of CGM. 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 4.2% a pH of 6.75, 17 ppm P, and 103 ppm K.
The experimental design is a randomized complete block with three replications. Individual experimental plots are 5 x 5 ft with five treatments. Corn gluten meal and urea are applied yearly to the same plots at an annual rate of 4 lbs N/1000 ft2 (Table 1). Treatments included split applications of 2 lb N/1000 ft2 and four applications of 1 lb N/1000 ft2. The CGM and urea are applied using cardboard containers as '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 2000, initial applications of all urea and CGM treatments were made on April 21. Sequential applications of 1 lb N/1000 ft2 were made on July 7, July 27, and September 5. The second applications of 2 lb N/1000 ft2 for urea and CGM (Treatment 3 and 5) were made on July 27.
Turf quality was monitored from May 2 through September 12 (Table 1). Visual turf quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst turf quality. Additional quality data were taken on October 27 because above-normal temperatures and moderate rainfall resulted in a 'greenup' of the turf.
Table 1. Visual quality1 of Kentucky bluegrass treated in the 1991 Corn Gluten Meal Weed Control Study.
|
Material |
Number of applications |
May 2 |
May 10 |
May 17 |
May 23 |
June 2 |
June 8 |
June 15 |
June 22 |
June 30 |
July 7 |
|
|
1 |
Untreated control |
NA |
7.0 |
6.7 |
6.7 |
6.7 |
6.0 |
6.3 |
6.0 |
6.0 |
6.7 |
7.0 |
|
2 |
Corn gluten meal |
4 |
6.3 |
6.3 |
6.7 |
7.3 |
7.3 |
7.7 |
7.7 |
7.3 |
7.3 |
7.7 |
|
3 |
Corn gluten meal |
2 |
6.0 |
6.7 |
6.7 |
7.0 |
8.0 |
8.0 |
8.3 |
8.7 |
8.0 |
8.0 |
|
4 |
Urea (46-0-0) |
4 |
7.0 |
8.7 |
7.7 |
7.7 |
6.7 |
7.3 |
7.0 |
7.3 |
7.3 |
7.7 |
|
5 |
Urea (46-0-0) |
2 |
7.7 |
8.3 |
7.7 |
8.3 |
8.0 |
7.7 |
8.3 |
8.3 |
8.7 |
8.3 |
|
LSD0.05 |
1.12 |
1.2 |
NS |
NS |
1.0 |
1.0 |
1.3 |
0.9 |
NS |
NS |
|
|
Material |
Number of applications |
July 14 |
July 25 |
Aug 2 |
Aug 8 |
Aug 16 |
Aug 24 |
Aug 29 |
Sept 5 |
Sept 12 |
Oct 27 |
Mean |
|
1 |
Untreated control |
NA |
6.3 |
7.0 |
6.3 |
6.3 |
6.0 |
6.0 |
6.0 |
6.3 |
4.7 |
5.0 |
6.3 |
|
2 |
Corn gluten meal |
4 |
8.0 |
8.0 |
9.0 |
8.0 |
7.7 |
8.0 |
9.0 |
7.0 |
5.0 |
8.3 |
7.5 |
|
3 |
Corn gluten meal |
2 |
7.0 |
7.3 |
7.0 |
7.3 |
7.7 |
7.7 |
7.7 |
7.3 |
5.0 |
6.7 |
7.3 |
|
4 |
Urea (46-0-0) |
4 |
8.7 |
8.3 |
8.3 |
8.7 |
8.3 |
8.0 |
8.3 |
6.7 |
4.3 |
8.0 |
7.6 |
|
5 |
Urea (46-0-0) |
2 |
6.7 |
7.0 |
7.0 |
7.7 |
8.7 |
8.7 |
7.7 |
6.7 |
5.0 |
6.7 |
7.7 |
|
LSD0.05 |
1.2 |
NS |
1.8 |
1.4 |
0.6 |
1.1 |
0.8 |
NS |
NS |
1.2 |
0.6 |
1
Visual quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst turf quality.2
These data are significantly different at the 0.06 level.Initial applications of all treatments were made on April 21. Sequential applications of treatments 2 and 4 were made on July 7, July 27, and September 5. The second applications of treatments 3 and 5 were made on July 27.
NS = means are not significantly different at the 0.05 level.
Crabgrass plants in the 1- to 3-leaf stage were found in late June. Crabgrass data represent the number of plants per individual plot. Crabgrass counts were made on August 16, August 29, and September 12 (Table 2).
Broadleaf weed populations were measured by either counting the number of plants or estimating the percentage cover per individual plot. Data for dandelion and clover were taken on April 26, May 17 (clover only), June 22, July 25, August 2, August 29, and September 12. Dandelion infestations were determined by counting the number of plants per individual plot. Clover populations were estimated by assessing the percentage area of each plot covered by clover.
Data were analyzed with the Statistical Analysis System (SAS, Version 6.12) and the Analysis of Variance (ANOVA) procedure. Effects of CGM and urea on bluegrass quality and weed control were examined using Fisher’s Least Significant Difference (LSD) means comparison tests.
The 2000 growing season was quite warm and dry with above-average temperatures and below-average rainfall from April through September. Supplemental irrigation was required throughout the season to keep the bluegrass in good condition.
In early May, bluegrass quality was improved on grass treated with urea. Response to CGM treatment was slower but the quality of urea and CGM treated turf was similar through June and better than the untreated control. As expected, quality improved following the sequential treatments of CGM and urea in July and August. By September, the high temperatures and below-normal rainfall caused the bluegrass to enter dormancy. Rainfall and moderate temperatures in October caused a late season greenup and on October 27, grass treated with CGM or urea on September 5 (Treatments 2 and 4) had significantly better quality than grass not receiving treatments on that date. Mean data for the entire season show that all CGM and urea-treated grass had better quality than untreated.
There were no statistically significant differences in weed populations between the treated and untreated bluegrass. Crabgrass populations were low in all plots (Table 2). There were fewer crabgrass plants in untreated bluegrass than in treated because of increased competition from broadleaf weeds in the untreated grass. Dandelion populations were similar in treated and untreated bluegrass (Table 3). There were slight numerical differences but none were statistically different. Percentage clover cover also was similar in the treated and untreated bluegrass (Table 4). Through August 29, clover cover was numerically greater in bluegrass treated with CGM and urea in split applications of 2 lb/1000 ft2 than in the untreated controls.
Table 2. Crabgrass counts1 in Kentucky bluegrass treated in the 1999 Corn Gluten Meal/Urea Weed Control Study.
|
Material |
lbs N /1000 ft2 |
Number of applications |
Aug 16 |
Aug 29 |
Sept 12 |
Mean |
|
|
1 |
Untreated control |
NA |
NA |
1.7 |
1.0 |
1.0 |
1.2 |
|
2 |
Corn gluten meal |
4 |
4 |
5.0 |
2.7 |
2.7 |
3.4 |
|
3 |
Corn gluten meal |
4 |
2 |
3.0 |
2.7 |
4.7 |
3.4 |
|
4 |
Urea (46-0-0) |
4 |
4 |
6.3 |
3.3 |
1.7 |
3.8 |
|
5 |
Urea (46-0-0) |
4 |
2 |
1.3 |
2.3 |
2.3 |
2.0 |
|
LSD0.05 |
NS |
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 1999 Corn Gluten Meal/Urea Weed Control Study.
|
Material |
Number of applications |
April 26 |
June 22 |
July 25 |
Aug 2 |
Aug 29 |
Sept 12 |
Mean |
|
|
1 |
Untreated control |
NA |
20.0 |
23.0 |
20.3 |
21.3 |
23.0 |
26.7 |
22.4 |
|
2 |
Corn gluten meal |
4 |
30.0 |
31.7 |
20.0 |
20.7 |
23.0 |
24.0 |
24.9 |
|
3 |
Corn gluten meal |
2 |
21.7 |
29.7 |
17.7 |
19.7 |
17.7 |
20.3 |
21.1 |
|
4 |
Urea (46-0-0) |
4 |
20.0 |
21.0 |
21.7 |
15.0 |
20.0 |
19.7 |
19.6 |
|
5 |
Urea (46-0-0) |
2 |
18.3 |
21.7 |
17.3 |
19.3 |
22.7 |
25.0 |
20.7 |
|
LSD0.05 |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
1
These values represent the number of dandelion plants per plot.NS = means are not significantly different at the 0.05 level.
Table 4. Percentage clover cover1 in Kentucky bluegrass treated in the 1999 Corn Gluten Meal/Urea Weed Control Study.
|
Material |
Number of applications |
April 26 |
May 17 |
June 22 |
July 25 |
Aug 2 |
Aug 29 |
Sept 12 |
Mean |
|
|
1 |
Untreated control |
NA |
6.7 |
31.7 |
41.7 |
33.3 |
26.7 |
23.3 |
16.7 |
25.7 |
|
2 |
Corn gluten meal |
4 |
17.3 |
36.7 |
28.7 |
33.3 |
33.3 |
30.0 |
16.7 |
28.0 |
|
3 |
Corn gluten meal |
2 |
23.3 |
46.7 |
55.0 |
43.3 |
36.7 |
31.7 |
15.0 |
36.0 |
|
4 |
Urea (46-0-0) |
4 |
18.7 |
36.7 |
33.7 |
33.3 |
20.0 |
13.7 |
6.7 |
23.2 |
|
5 |
Urea (46-0-0) |
2 |
28.7 |
45.0 |
45.0 |
38.3 |
31.7 |
31.7 |
16.7 |
33.9 |
|
LSD0.05 |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
1
These values represent the area per plot covered by clover.NS = means are not significantly different at the 0.05 level.