1998 Iowa Turfgrass Research Report
1996-97 Aquatrols Creeping Bentgrass Fertilizer Study
Barbara R. Bingaman, Nick E. Christians, and Michael B. Faust
The purpose of this study was to compare several different fertilizers in a fall fertilization program on creeping bentgrass maintained at fairway height. The experimental plot was in an established fairway height area of 'Penneagle' Creeping Bentgrass grown on native soil at the Iowa State University Horticulture Research Station north of Ames, Iowa. The pH of the soil was 8.0, the P level was 14 lb/A and the K level was 140 lb/A.
The experiment was arranged in a randomized complete block design. Individual plots were 5 x 5 ft with three replications. Three-foot barrier rows were placed between replications to facilitate taking clippings. Fertilizers were applied in the fall of 1996 shortly before the bentgrass ceased actively growing for the season (15-30 days).
The reason for the timing of application was that in the fall photosynthesis was still occurring and the plants would use the nutrients to increase root growth and carbohydrate levels. The resulting turf stand, therefore, should have better winter hardiness and an improved response (earlier greenup and higher quality) in the spring.
Single applications of five fertilizer formulations were made on October 24, 1996. Untreated Urea (46-0-0), Fertilizer Plus 0.5% (46-0-0), and Fertilizer Plus 1.0% (46-0-0) were applied at 0.5 and 1.0 lb N/1000 ft2. Fertilizer A (17-10-12) and Fertilizer B (22-4-14) were applied at 0.6 lb N/1000 ft2. An untreated control will be included for a total of 10 treatments (Table 1). The fertilizers were applied using plastic coated containers as 'shaker dispensers'.
Post treatment observations were made in the fall of 1996. The plots were checked on October 28 and periodically throughout the fall for phytotoxicity and quality differences. Greenup began on March 13 and all plots were green by April 18, 1997. Greenup data were recorded using a 9 to 1 scale: 9 = 100% green, 6 = 50% green, 1 = 100% brown turf (Table 1). Visual quality data were taken on April 18, May 22, and May 30 (Table 1). Visual quality was assessed using a 9 to 1 scale: 9 = best, 6 = lowest acceptable, and 1 = worst quality.
On May 22, the plots were mowed to 3/8" and clippings were collected. Fresh clipping weights were taken (Table 1). The clippings were dried for 96 hours at 67° C and dry weights were measured (Table 1). The dry tissue was ground to 40 mesh using a Wiley Laboratory Mill and submitted for tissue nutrient and carbohydrate analysis.
Tissue nutrient analyses were conducted by the Plant Nutrition Lab in the Department of Horticulture at Iowa State University using an IRIS - AP - Duo, Inductively Coupled Argon Plasma Analyzer (ICAP). Nitrogen was determined as percent N on a dry weight basis. Tissue content of boron, copper, manganese, molybdenum, nickel, and zinc were determined in ppm. The percent content in leaf tissue levels of calcium, potassium, magnesium, and phosphorus also were evaluated (Tables 2 and 3).
Total non-structural carbohydrate content (TNC) analyses was conducted by the Agronomy Forage Lab in the Department of Agronomy at Iowa State University. The acid extraction procedure for removing total non-structural carbohydrate and the phenol-sulfuric acid calorimetric method for total carbohydrate analysis were used. This methodology followed the guidelines in Chemical & Biological Methods for Grain & Forage Sorghum, Department of Agronomy, International Programs in Agriculture, Purdue University. The carbohydrate levels were determined as percent by weight on a dry matter basis (Table 3).
Root cores were taken on May 29. Five cores were taken from each plot. The cores were split into three sections by depth (0-5, 5-10, and 10-15 cm). The roots were extracted from the soil using water and a series of screens with various mesh sizes. The roots were dried at 100° C and dry weights were taken. The roots were 'ashed' in a muffle furnace at 500° C to burn off the root tissue. The residue was weighed and root weights were calculated by subtracting the ashed remnants from the dry root weights (Table 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 tests (LSD) were used to compare means.
There was a difference in spring greenup between the grass in the control and all other treatments. The grass treated with the fertilizer plus 1% treatment at 1 lb N/1000 ft2 had the highest rating (Table 1). The fresh clipping and dry clipping weights were also highest for that treatment.
There were significant differences in tissue N content (Table 2). The grass in the control had the lowest N content as would be expected. The grass treated with the fertilizer plus 1% treatment at 1 lb N/1000 ft2 contained the highest N content.
Phosphorus tissue content was highest in the grass treated with the 17-10-12 fertilizer (Table 3). This again would be expected because of the lack of P in most of the other treatments. There were no differences in carbohydrate content among the treatments.
Root weight of the grass varied among the treatments at the 0-5 cm depth only (Table 4). It was generally the grass treated with the 0.5 lb N/1000 ft2 treatment levels that had the highest rooting. The exception was treatment 6, the 1 lb N/1000 ft2 treatment with the 0.5% fertilizer plus treatment.
Table 1. Spring 1997 greenup1, visual quality2 and clipping weight3 data for creeping bentgrass in the 1996-97 Bentgrass Fertilizer Study.
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lb N/1000 ft2 |
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Untreated control |
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278.5 |
95.1 |
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Untreated urea (46-0-0) |
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341.3 |
113.4 |
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Untreated urea (46-0-0) |
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355.4 |
115.5 |
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Fertilizer Plus 0.5 (46-0-0) |
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302.2 |
99.1 |
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Fertilizer Plus 1.0 (46-0-0) |
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333.6 |
108.1 |
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Fertilizer Plus 0.5 (46-0-0) |
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341.5 |
111.8 |
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Fertilizer Plus 1.0 (46-0-0) |
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412.9 |
134.5 |
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Fertilizer A (17-10-12) |
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351.4 |
114.0 |
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Fertilizer B (22-4-14) |
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341.5 |
110.8 |
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LSD0.05 |
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(p>.10) |
Fertilizers applied on October 24, 1996.
NS = means not significantly different at the 0.05 level.
1Greenup was assessed using a 9 to 1 scale: 9 = 100% green, 6 = 50% green, and 1 = 100% brown turf.
2Visual quality ratings were based on a 9 to 1 scale: 9 = best, 6 = lowest acceptable, and 1 = worst quality.
3Height for clippings was 3/8".
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ISU Horticulture:Publications:1998 Turfgrass Report | College of Agriculture |