1998 Iowa Turfgrass Research Report

1998 Iowa Turfgrass Research Report

1991 Corn Gluten Meal Crabgrass Control Study - Year 7

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

A study screening corn gluten meal (CGM) for efficacy as a natural product herbicide and fertilizer in turf was begun in 1991 and has been continued on the same plot for seven consecutive years. It is being conducted at the Iowa State University Research Station north of Ames, IA. The experiment is located 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 3.6% a pH of 7.1, 4.5 ppm P, and 101 ppm K.

The experimental design is a randomized complete block. Individual experimental plots are 5 x 5 ft with three replications. There are seven treatments including CGM at 20, 40, 60, 80, 100, and 120 lbs/1000 ft² and an untreated control (Table 1). Because corn gluten meal is 10% N, these rates are equivalent to 2, 4, 6, 8, 10, and 12 lb N/1000 ft². All treatments were made to the same plots as in previous years. The CGM was applied in a single, early spring preemergence application on April 18, 1997 using 'shaker dispensers'.

The materials were watered-in with the irrigation system. Supplemental irrigation was used to provide adequate moisture to maintain the grass in good growing condition.

The plot was monitored throughout the season for turf quality, and weed control. Visual turf quality was assessed using a 9 to 1 scale: 9 = best, 6 = lowest acceptable, and 1 = worst turf quality. Quality data were taken on June 5, June 25, July 21, July 30, and August 20 (Table 1).

Weed control was measured by either counting the number of plants or estimating the percentage cover per individual plot. Broadleaf species (dandelion and clover) and annual grasses (crabgrass) were surveyed. Data were taken for dandelion and clover on June 5, July 30, and August 20. Crabgrass data were taken on July 30 and August 20. Crabgrass germination was noted on June 6.

Data were analyzed with the Statistical Analysis System version 6.10 (SAS Institute, 1989) and the Analysis of Variance (ANOVA) procedure. Fisher's Least Significant Difference (LSD) means comparison tests were used to assess CGM effects on bluegrass quality and weed control. Weed control data were converted to percentage reductions as compared with the untreated controls.

It was an unusually cool, dry, and windy spring. The usual greenup was more subtle this year. Bluegrass did not respond to CGM treatments as dramatically as in the past. The nitrogen response was slower and was not uniform within individual plots.

There was no phytotoxicity observed in the Kentucky bluegrass treated with CGM. Turf quality was significantly better in CGM treated bluegrass than the untreated control for the entire season (Table 1). The best quality was in turf receiving the highest level of CGM.

Crabgrass populations were low in the untreated controls because the dandelion and clover infestations were large and well established before crabgrass germination. Corn gluten meal at 40, 60, 80, 100, and 120 lb resulted in numerical reductions in the number of crabgrass plants as compared with the untreated control on August 2 (Table 2). Crabgrass reductions were lower in 1997 when compared with data over the previous six years (Table 5).

Percentage reductions of dandelion numbers and clover cover were similar to those found in previous years (Table 6). Treatment with CGM at all levels in 1997 except at 20 lb significantly reduced dandelion populations (Table 3). Clover cover was significantly reduced by all levels of CGM as compared with the untreated control (Table 4).

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	June 5	June 25	July 21	July 30	August 20	Mean quality
1	Untreated control	0	0	5	5	5	6	5	5
2	Corn gluten meal	20	2	6	6	6	7	6	6
3	Corn gluten meal	40	4	7	7	7	7	7	7
4	Corn gluten meal	60	6	8	7	8	7	7	8
5	Corn gluten meal	80	8	8	8	9	8	8	8
6	Corn gluten meal	100	10	8	8	9	8	8	8
7	Corn gluten meal	120	12	9	8	9	8	9	9
	LSD0.05			1	1	1	NS	1	1

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

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

Table 2. Number of crabgrass plants¹ in Kentucky bluegrass plots treated in the 1991 Corn Gluten Meal Weed Control Study.

			Crabgrass counts				Percentage Reduction2
	Material	lbs CGM /1000 ft2	July 30	Aug 20	Mean		July 30	Aug 20	Mean
1	Untreated control	0	2	7	5		0	0	0
2	Corn gluten meal	20	8	11	10		0	0	0
3	Corn gluten meal	40	1	1	1		67	82	79
4	Corn gluten meal	60	1	1	1		83	82	82
5	Corn gluten meal	80	2	2	2		0	73	54
6	Corn gluten meal	100	1	1	1		67	82	79
7	Corn gluten meal	120	1	1	1		67	86	82
	LSD0.05		NS	6	(P > 0.06) 6		NS	NS	NS

¹These values represent the number of crabgrass plants per plot.

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

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

ISU Horticulture:Publications:1998 Turfgrass Report

College of Agriculture