1999 Iowa Turfgrass Research Report

'Penneagle' Creeping bentgrass maintained at fairway height (0.5 inches) was evaluated after treatment with Proxy 2SL (ethephon). This study was conducted at the Iowa State University Horticulture Research Station located north of Ames, IA.

The study was arranged as a randomized complete block with 3 replications. Individual plot size was 5 x 5 ft with 3 ft barrier rows between replications. Chipco Proxy was applied at 0, 4.7, 6.0, and 12.0 fl oz/1000 ft² (Table 1).

There were four applications at these rates made at four week intervals. The first application was made on June 22, 1998 on Penneagle established on a native (Nicollet) soil. Because of construction in this area, the July, August, and September applications were made on a relocated plot of 'Penneagle' established on a soil composed of 1 part peat, 1 part Nicollet soil, and 1 part sand. Subsequent applications on the relocated site were made on July 23, August 20, and September 23. The Proxy was applied in 283 ml water/plot, which translates to an application rate of 3 gal/1000 ft². Applications were made at 30 psi with a carbon dioxide backpack sprayer equipped with Teejetâ #8006 flat fan nozzles.

Turf quality and color data were evaluated on a weekly basis following all applications and for six weeks following the last application. Turf quality was based on color, uniformity, and turf density and was based on a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality. Visual observations of phytotoxicity were made weekly following all applications and for 6 weeks following the last application. Phytotoxicity was recorded as either present or absent. Fresh clipping weights were taken on a weekly basis when there was sufficient growth. Mowing height for collecting clippings was 0.5 in.

The data from the original and relocated plots were analyzed separately and are presented in discrete tables. All data were analyzed with the Statistical Analysis System (SAS, Version 6.12) and the Analysis of Variance (ANOVA) procedure. Treatment effects were examined with Fisher's Least Significant Difference means separation test (LSD).

Original Study

Turf quality data were taken from the original plot on June 30, July 7, July 15, July 23, and July 30 (Table 1). Clippings were gathered on June 30, July 7, and July 30 (Table 2).

On July 7, the bentgrass surfaces in the original plot were examined using a Clegg Impact Soil Tester that measured surface hardness. Readings of 'hardness' were taken at 3 and 6 inch drop heights. Six readings per plot were taken and the highest and lowest readings were deleted. The remaining 4 values were averaged for each plot and each height. The means for each plot were analyzed (Table 3).

The only significant differences in turf quality were recorded on July 15 (Table 1). All treated bentgrass had poorer quality than the untreated controls on July 15 but the quality was still above the lowest acceptable rating of 6.0.

There were no statistical differences in clipping weights on any of the collection dates (Table 2). On July 7, the numerical differences between the treated and untreated bentgrass were quite large. The clipping weight of turf treated with Proxy 2SL at 12.0 fl oz/1000 ft² was almost twice that of the untreated controls and Proxy at the lower rates produced at least a 150% increase in clippings as compared with untreated turf.

Measurements with the Clegg Impact Soil Tester showed very little difference in hardness of the bentgrass surface among the treatments (Table 3). Hardness was similar for treated and untreated turf at the 3 and 6 inch heights.

Relocated Study

Quality ratings were made for the relocated plot on August 5, August 12, August 20, August 27, September 4, September 11, September 17, September 23, October 2, October 9, October 15, October 22, and October 30 (Table 4-5). Clippings were taken from the relocated plot on August 12, September 4, September 11, September 23, and October 9 (Table 6).

There were no differences in visual quality between treated and untreated bentgrass until October 9 (Table 4-5). Significant reductions in quality were found in all treated bentgrass from October 9 through October 30. The quality of the treated turf during this period did not drop below the lowest acceptable rating of 6.0.

Clipping weights were not significantly reduced by the treatments as compared with the untreated controls at any of the test dates (Table 6).

 

Table 1. Visual quality¹ of 'Penneagle' creeping bentgrass treated in the 1998 Fairway Bentgrass Growth Regulator Study for June 30 through July 30 (on original site).

	Material	Rate (fl oz/1000 ft2)	June 30	July 7	July 15	July 23	July 30	Mean
1	Untreated control	N/A	9.0	8.0	9.0	8.0	8.0	8.4
2	Chipco Proxy 2SL	4.7	7.0	8.0	7.7	8.0	8.0	7.7
3	Chipco Proxy 2SL	6.0	7.0	8.0	8.0	8.0	8.0	7.8
4	Chipco Proxy 2SL	12.0	7.0	8.0	8.0	8.0	8.0	7.8
	LSD0.05		--	--	0.6	--	--	0.1

¹Visual quality assessments were made using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality.

-- = Fisher's Least Significant Difference means separation test is not valid for these data.

 

Table 2. Fresh clipping weights¹ of 'Penneagle' creeping bentgrass treated in the 1998 Fairway Bentgrass Growth

Regulator Study (on original site).

	Material	Rate (fl oz/1000 ft2)	June 30	July 7	July 30	Mean weight
			____________________ g ____________________
1	Untreated control	N/A	12.1	22.0	23.4	19.2
2	Chipco Proxy 2SL	4.7	13.0	34.1	23.6	23.6
3	Chipco Proxy 2SL	6.0	19.7	33.2	24.2	25.7
4	Chipco Proxy 2SL	12.0	15.8	42.7	23.9	27.5
	LSD0.05		NS	NS	NS	NS

¹Fresh clipping weights represent grams fresh tissue.

Applications were made on June 22.

-- = Fisher's Least Significant Difference means separation test is not valid for these data.

	Material	Rate (fl oz/1000 ft2)	3 inch height	6 inch height
1	Untreated control	N/A	28.8	42.5
2	Chipco Proxy 2SL	4.7	26.8	50.3
3	Chipco Proxy 2SL	6.0	28.8	44.1
4	Chipco Proxy 2SL	12.0	27.9	46.0
	LSD0.05		NS	NS

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

 

Table 4. Visual quality¹ of 'Penneagle' creeping bentgrass treated in the 1998 Fairway Bentgrass Growth Regulator Study for August 5 - September 17 (on relocated site).

	Material	Rate (fl oz/1000 ft2)	Aug 5	Aug 12	Aug 20	Aug 27	Sept 4	Sept 11	Sept 17
1	Untreated control	N/A	9.0	9.0	6.0	7.0	8.0	6.0	7.0
2	Chipco Proxy 2SL	4.7	9.0	9.0	6.0	7.0	8.0	6.0	7.0
3	Chipco Proxy 2SL	6.0	9.0	9.0	6.0	7.0	8.0	6.0	7.0
4	Chipco Proxy 2SL	12.0	9.0	9.0	6.0	7.0	8.0	6.0	7.0
	LSD0.05		--	--	--	--	--	--	--

¹Visual quality assessments were made using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality.

-- = Fisher's Least Significant Difference means separation test is not valid for these data.

 

Table 5. Visual quality¹ of 'Penneagle' creeping bentgrass treated in the 1998 Fairway Bentgrass Growth Regulator Study for September 23 - October 30 (on relocated site).

	Material	Rate (fl oz/1000 ft2)	Sept 23	Oct 2	Oct 9	Oct 15	Oct 22	Oct 30	Mean
1	Untreated control	N/A	9.0	8.0	9.0	9.0	8.0	8.0	8.4
2	Chipco Proxy 2SL	4.7	9.0	8.0	7.3	7.0	6.0	6.7	7.7
3	Chipco Proxy 2SL	6.0	9.0	8.0	7.0	7.3	6.0	6.3	7.8
4	Chipco Proxy 2SL	12.0	9.0	8.0	6.3	7.0	6.0	7.0	7.8
	LSD0.05		--	--	1.7	0.6	0.7	1.0	0.1

¹Visual quality assessments were made using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality.

-- = Fisher's Least Significant Difference means separation test is not valid for these data.

 

Table 6. Fresh clipping weights¹ of 'Penneagle' creeping bentgrass treated in the 1998 Fairway Bentgrass Growth Regulator Study (on relocated site).

	Material	Rate (fl oz/1000 ft2)	Aug 12	Sept 4	Sept 11	Sept 23	Oct 9	Oct 30	Mean
			__________________________ g __________________________
1	Untreated control	N/A	1.0	63.7	25.3	17.5	22.8	20.0	25.0
2	Chipco Proxy 2SL	4.7	1.4	62.3	30.0	13.8	23.5	15.7	24.4
3	Chipco Proxy 2SL	6.0	1.4	76.7	26.0	16.8	24.6	13.5	26.5
4	Chipco Proxy 2SL	12.0	1.6	98.3	42.0	12.9	21.9	16.5	32.2
	LSD0.05		NS	NS	NS	NS	NS	NS	NS

¹Fresh clipping weights represent grams fresh tissue.

Applications were made on July 23, August 20, and September 23.

ISU Horticulture:Publications:1999 Turfgrass Report

College of Agriculture