1999 Iowa Turfgrass Research Report

This creeping bentgrass establishment trial was initiated on 1 Sept. 1996 at the Iowa State University Horticulture Research Station. Data from the 1998 growing season are discussed in this report. The study was conducted to observe the development of creeping bentgrass from seed grown in a sand-based golf course green and to study the effects of liquid and granular fertilizer applications on the quality of mature bentgrass.

The objectives of the study were i) to compare the effects of five different combinations of organic-based fertilizer products and a control on the establishment of creeping bentgrass (Agrostis palustris Huds. cv. Crenshaw), and ii) to compare the effects of two different application frequency schedules on the quality of mature creeping bentgrass.

The research was conducted on a 100% sand-based golf green. The rooting material contained 10% calcium carbonate (CaCO₃) and had a pH of 8.2. Physical analysis of the sand particles showed the rooting medium to be within the standards set by the United States Golf Association (USGA) for golf course green construction. The research, with a 900 ft² area, was conducted as a split-plot design with six treatments as main plots and two application frequency schedules as subplots. The study included three replications. Each experimental plot (36 total) had an area of 25 ft².

The main plots of the research consisted of five liquid fertilizer products and a granular fertilizer material (Tables 1, 2, and 3). Four of the liquid treatments, excluding the control, were general use organic soil conditioners designed to stimulate microbial activity and to provide overall improved soil fertility. The organic liquid treatments were mixed in solution with NH₄NO₃ and KNO₃ to supply adequate nitrogen and potassium requirements of the plant. The control treatment contained only the inorganic nitrogen (NH₄NO₃) and potassium (KNO₃) sources. All of the liquid treatments contained the same rate of nitrogen and potassium, and they were applied to the turf using a CO₂ tank and hand-held spray boom. Granular treatments were applied with a hand-held shaker to match the N and K rates of the liquid products.

The first application to experimental plots in the spring of 1998 occurred on 21 May. The application frequency schedule established in 1997, where half of the experimental plots received one application every two weeks and the other half of the plots received two applications per week, was continued in 1998. Plots treated once every two weeks received 0.25 lb N and 0.125 lb K/1000 ft²/application. Plots treated two times per week received 0.0625 lb N and 0.0313 lb K/1000 ft²/application. All plots received 0.5 lb N and 0.25 lb K/1000 ft²/month irregardless of application frequency schedule or treatment differences.

Clipping tissue samples were collected three times during the 1998 season. Individual collection dates were 17 and 31 August, and 14 September. Clippings were taken 3 to 4 days following the fourth and eighth 0.0625 lb N/1000 ft² treatment application when all plots had received identical N and K rates. The clippings were dried at 68 öC for 48 h, dry-ashed, diluted with acid, and analyzed for nutrient content by inductively coupled argon plasma spectrometry (ICAP). Plant tissue nitrogen content was determined using the total Kjeldahl nitrogen procedure (TKN).

One root sample was taken during the 1998 growing season on 1 October. Five one-inch diameter cores were removed from random locations on each plot at a depth of 15 cm. The roots were washed from the sand media using a screening technique. The extracted root material was dried at 68 öC for 48 h. An oven-dry root mass was taken and the samples were placed into a muffle furnace for 12 h at a temperature of 500 öC. A second root weight was taken following the ashing procedure. The actual dry root mass of plants grown on each experimental plot was determined by subtracting the dry-ashed root mass from the oven-dry root mass.

Visual quality data, rating density and color of each plot was taken four times in 1998. The data was collected 17 and 31 August, and 8 and 14 September. Quality was rated on a 1 to 9 scale; where 1 = poor quality and 9 = highest quality.

Results from clipping analysis are shown in Tables 1 and 2. The tables have been divided into macronutrient (Table 1) and micronutrient (Table 2) concentrations of turfgrass tissue.

Differences in plant shoot tissue concentration due to treatment effects were shown for the elements nitrogen (N), phosphorus (P), magnesium (Mg), copper (Cu), and molybdenum (Mo) (Tables 1 and 2). Compared to the five liquid treatments, the granular treatment provided the highest tissue N, P, and Mg concentrations. Plants grown in control plots had the lowest tissue N levels. Phosphorus shoot tissue concentration of plants grown using the granular treatment was on average 36% higher than plants supplied with the liquid treatments. Tissue P concentrations were probably higher because the granular product contained 3% P₂O₅ (12-3-9 formulation). Phosphorus was not supplied to plots receiving the liquid treatments throughout the 1998 growing season. Plants fertilized by the liquid treatments had significantly more Cu in the shoot tissue as compared to those plants grown using the granular material. Plants grown using the control and granular treatments had significantly lower Mo tissue levels as compared to the other liquid treatments. The high organic matter content of the granular product may have complexed Cu and Mo reducing the ability of the plant to absorb these elements.

Application frequency of treatments (2 vs. 8 applications/month) caused differences in shoot tissue concentration for the elements: nitrogen (N), copper (Cu), and molybdenum (Mo) (Tables 1 and 2). Nitrogen shoot tissue concentration was 3% higher for plants grown in plots receiving 8 applications/month compared to those plants receiving 2 applications/month. Shoot tissue concentrations were 6% and 8% higher for Cu and Mo, respectively, in plots receiving 8 applications/month compared to the plots which received 2 applications/month. However, plants grown in plots receiving 2 applications/month had an average 8% higher shoot tissue Mn concentration compared to plants grown in plots that received 8 applications/month.

Mean visual quality data taken throughout 1998 showed differences among fertilizer treatments (Table 3). The granular product (treatment 6) had significantly higher visual quality ratings compared to the liquid treatments. The better visual quality could be explained by the shoot tissue nutrient concentration data which showed the highest N levels in plants treated with the granular feather meal product. Plots receiving 8 applications per month had a higher visual quality rating than plots receiving 2 applications/month.

No differences were shown between treatments or application frequency schedules for root development of grass plants (Table 3). These findings are similar to rooting data taken in 1997.

Table 1. Mean macronutrient tissue concentration and analysis of variance.

	Macronutrientsz
Treatment	Nitrogen (N)	Phosphorus (P)	Potassium (K)	Calcium (Ca)	Magnesium (Mg)	Sulfur (S)
	% of dry tissue
22% humic acid	3.39	0.26	1.83	0.74	0.28	0.25
6-0-0 w/ organic acids	3.45	0.26	1.87	0.72	0.27	0.25
15% humic acid	3.44	0.26	1.87	0.70	0.26	0.25
5-3-2 w/ molasses	3.36	0.26	1.89	0.70	0.26	0.26
Control	3.23	0.25	1.85	0.74	0.27	0.25
12-3-9 ground feather meal	3.47	0.40	1.87	0.77	0.30	0.25
LSD(0.05)y	0.14	0.02	NS	NS	0.02	NS
Application Frequency
2 apps/month	3.34	0.28	1.85	0.74	0.28	0.25
8 apps/month	3.43	0.28	1.87	0.71	0.27	0.25
LSD(0.05)y	0.08	NS	NS	NS	NS	NS
Anovax Prob > F
Treatment	0.0146	0.0001	0.5884	0.2256	0.0038	0.2515
Application frequency	0.0303	0.1851	0.3652	0.1965	0.2247	0.1076
Trt*Application frequency	0.0053	0.6029	0.2056	0.4941	0.7280	0.3067

^zData shown are the mean of three tissue collection dates during the 1998 growing season. Individual collection dates were 17 and 31 August, and 14 September.

^yMean separation within columns by Fisher's least significant difference test.

^xSignificant differences occur at the P æ 0.05 level

Table 2. Mean micronutrient tissue concentration and analysis of variance.

	Micronutrientsz
Treatment	Boron (B)	Copper (Cu)	Iron (Fe)	Manganese (Mn)	Molybdenum (Mo)	Sodium (Na)	Zinc (Zn)
	mg / kg
22% humic acid	5.37	8.80	213.17	158.17	2.93	64.08	61.49
6-0-0 w/ organic acids	5.52	9.33	205.44	148.37	2.78	60.56	61.47
15% humic acid	5.43	8.82	170.28	158.77	2.92	60.43	62.70
5-3-2 w/ molasses	5.44	8.89	171.33	163.56	2.86	59.66	64.21
Control	5.57	8.99	214.61	166.41	2.61	62.11	62.08
12-3-9 ground feather meal	5.38	6.98	230.89	158.95	2.39	70.07	64.16
LSD(0.05)y	NS	0.87	NS	NS	0.31	NS	NS
Application Frequency
2 apps/month	5.47	8.37	206.06	165.32	2.64	62.00	62.94
8 apps/month	5.44	8.90	195.85	152.76	2.86	63.63	62.43
LSD(0.05)y	NS	0.50	NS	11.18	0.18	NS	NS
Anovax Prob > F
Treatment	0.8838	0.0002	0.2186	0.5175	0.0082	0.0751	0.7501
Application frequency	0.7977	0.0387	0.5379	0.0294	0.0198	0.4422	0.7220
Trt*Application frequency	0.8349	0.3775	0.8895	0.8790	0.1156	0.6871	0.9758

^zData shown are the mean of three tissue collection dates during the 1998 growing season. Individual collection dates were 17 and 31 August, and 14 September.

^yMean separation within columns by Fisher's least significant difference test.

^xSignificant differences occur at the P æ 0.05 level.

Table 3. Visual quality, rooting data, and analysis of variance.

	Visual Qualityz						Root Mass (g)
Treatment	Aug 17	Aug 31	Sept 8	Sept 14	Mean		October 1
22% humic acid	6.5	6.8	6.7	7.5	6.9		0.56
6-0-0 w/ organic acids	7.3	6.5	6.7	6.8	6.8		0.56
15% humic acid	6.7	6.8	6.5	7.0	6.8		0.52
5-3-2 w/ molasses	6.7	7.2	7.2	6.8	7.1		0.58
Control	7.0	6.5	6.7	7.5	6.8		0.53
12-3-9 ground feather meal	7.5	7.7	7.7	7.8	7.7		0.63
LSD(0.05)y	NS	0.8	0.6	0.5	0.4		NS
Application Frequency
2 apps/month	6.7	6.6	6.5	7.0	6.7		0.56
8 apps/month	7.2	7.3	7.3	7.5	7.3		0.57
LSD(0.05)y	0.4	0.4	0.3	0.3	0.3		NS
Anovax   Prob>F
Treatment	0.0955	0.0425	0.0031	0.0029	0.0023		0.1325
Application frequency	0.0213	0.0031	0.0001	0.0031	0.0001		0.7084
Trt*Application frequency	0.2090	0.4362	0.0302	0.3320	0.1224		0.9255

^zVisual quality (Color and Density) was rated on a 9 to 1 scale: 1=poor quality; 9=highest quality.

^yMean separation within columns by Fisher's least significant difference test.

^xSignificance occurs at the Pæ0.05 level.  

ISU Horticulture:Publications:1999 Turfgrass Report

College of Agriculture