1998 Iowa Turfgrass Research Report

1998 Iowa Turfgrass Research Report

1995 Corn Gluten Meal Rate Weed Control Study - Year 3

Barbara R. Bingaman, Nick E. Christians, and Michael B. Faust

Corn gluten meal (CGM) was screened for efficacy as a natural product herbicide in turf. This trial is a long-term study begun in 1995 that will be continued on the same area for several years. It is being conducted at the Iowa State University Horticulture Research Station north of Ames, IA. The experiment is in an area of '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 7.0, 3 ppm P, and 110 ppm K. The initial broadleaf weed population exceeded 50% cover on most of the test area.

The experimental design is a randomized complete block. Individual experimental plots are 10 x 10 ft with three replications. Corn gluten meal will be applied 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 (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 were included with an untreated control.

Initial applications were made on April 18. The second application for treatment 2 was made on June 3, the third on July 30, and the final on September 5. Sequential application of treatment 3 was made on August 6.

The experimental plot was checked for phytotoxicity after applications. Visual quality was measured using a 9 to 1 scale: 9 = best and 6 = lowest acceptable, and 1 = worst quality (Table 1). Visual quality data were taken on May 21, June 5, June 10, June 18, July 2, July 21, July 30, and August 20. Crabgrass control was assessed by estimating the percentage crabgrass cover per individual plot on July 30 and by counting the number of plants per individual plot on August 20 (Table 2). Dandelion control was measured by estimating the percentage of area covered in each plot on June 5 and by counting the number of plants per plot on August 20 (Table 3). Clover control was recorded by estimating the percentage of area covered in each plot on June 5, July 30, and August 20 (Table 4). Weed control data were converted to express percentage reductions as compared with the untreated control (Tables 2, 3, and 4).

Data were analyzed with the Statistical Analysis System (SAS) version 6.10 and the Analysis of Variance (ANOVA) procedure. Fisher's Least Significant Difference test (LSD) was used to compare means.

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 each data collection date except July 21 (Table 1).

Broadleaf weed species were well established when the crabgrass was emerging especially in the untreated controls. Competition from the broadleaves and the mature turf probably prevented the establishment of large crabgrass populations within the untreated plots. Consequently crabgrass cover was low in the untreated turf. Corn gluten meal did cause numerical reduction in crabgrass cover as compared with the untreated control but the differences were not statistically different (Table 2).

Crabgrass numbers were decreased by CGM at 10 lb in four applications (treatment 2), by split applications at 20 lb (treatment 3), and by an initial 30 lb application followed by 10 lb (treatment 4) as compared with the untreated control (Table 3). There were more crabgrass plants in turf receiving an initial application of CGM at 40 lb (treatment 5) than in the untreated control. The level of control with CGM applied in split applications at 20 lb (treatment 3) was consistent for 1995, 1996, and 1997. In 1997, crabgrass control was better than 1995 and 1996 for CGM at 10 lb applied four times (treatment 2).

Percentage dandelion cover was reduced by all levels of CGM as compared with the untreated control (Table 4). In 1997, CGM at all levels except at 30 lb followed by 10 lb (treatment 4) provided „ 50% reductions in cover as compared with the untreated control. In 1996, the CGM at these rates provided „ 48% reductions.

Corn gluten meal at all levels reduced the number of dandelions as compared with the untreated control (Table 5). The best control was provided by CGM at 10 lb in four applications and CGM at 20 lb in split applications.

Percentage clover cover was significantly reduced by CGM at all levels as compared with the untreated control. Percentage reductions for 1997 were „ 64% in all treated turf. Clover control was better in 1997 than 1996 in turf treated with CGM at 10 lb in four applications and CGM at 20 lb in split applications (Table 7).

Table 1. Visual quality¹ of Kentucky bluegrass treated in the 1995 Corn Gluten Meal Rate Weed Control Study.

	Material	Rate (lb product/1000 ft2)	May 21	June 5	June 10	June 18	July 2	July 21	July 30	Aug 20	Mean
1.	Untreated control	0	6	6	6	6	6	6	6	6	6
2.	Corn gluten meal	10 fb 10 fb 10 fb 10	7	7	7	7	9	7	8	8	8
3.	Corn gluten meal	20 fb 20	8	8	8	7	8	7	7	8	8
4.	Corn gluten meal	30 fb 10	7	9	9	8	9	8	8	8	8
5.	Corn gluten meal	40	7	9	9	9	9	8	8	8	8
	LSD0.05		1	1	1	1	1	NS	1	2	1

¹Visual quality was assessed using a 9 to 1 scale: 9 = best, 6 = lowest acceptable, and 1 = worst turf quality.

Table 2. Percentage crabgrass cover per plot¹ in Kentucky bluegrass treated in the 1995 Corn Gluten Meal Rate Weed Control Study.

	Material	Rate (lb product/1000 ft2)	Percentage crabgrass cover		Percentage cover reductions
			___________________ %__________________
1.	Untreated control	NA	22		0
2.	Corn gluten meal	10 fb 10 fb 10 fb 10	10		54
3.	Corn gluten meal	20 fb 20	7		66
4.	Corn gluten meal	30 fb 10	9		60
5.	Corn gluten meal	40	17		22
	LSD0.05		NS		NS

¹Percentage crabgrass cover data represent the area per plot covered by crabgrass.

²These values represent the percentage reduction in crabgrass cover per plot as compared with the untreated controls.

All treatments were at an annual rate of 4 lb N/1000 ft². Initial applications were made on April 18. The second application of treatment 2 was made on June 3, the third on July 30, and the final on September 5. The sequential application of treatment 3 was made on August 6.

NS = means are not significantly different at the 0.05 level.

Table 3. Crabgrass counts per plot¹ and percentage crabgrass reductions² in Kentucky bluegrass treated in the 1995 Corn Gluten Meal Rate Weed Control Study for 1995, 1996, and 1997.

			1995		1996				1997
	Material	Rate (lb product/1000 ft2)	Crabgrass reduction2		Crabgrass counts1		Crabgrass reduction2		Crabgrass counts1		Crabgrass reduction2
			_____ %_____		_______________ %_______________				_______________ %_______________
1.	Untreated control	NA	0		4		0		36		0
2.	Corn gluten meal	10 fb 10 fb 10 fb 10	28		7		0		19		48
3.	Corn gluten meal	20 fb 20	45		3		33		18		50
4.	Corn gluten meal	30 fb 10	44		1		67		14		61
5.	Corn gluten meal	40	54		5		0		37		0
	LSD0.05		NS		NS		NS		NS		NS

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.

ISU Horticulture:Publications:1998 Turfgrass Report

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