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Bohan Liu and Peter J. Landschoot

Phosphorus (P)-containing starter fertilizers are often recommended for establishing new turf, regardless of P levels indicated by the soil test. However, few field studies have been conducted to determine the effects of P in starter fertilizer on the rate of turf establishment. The primary objective of this study was to determine if P in starter fertilizer enhances tall fescue groundcover and growth during establishment on silt loam soil. This 2-year field study was conducted on silt loam soil tilled with a rototiller or core-aerated and vertically sliced. Mehlich-3 P levels ranged from 38 to 270 mg·kg−1. Experiments were conducted during late summer and fall, and all tests were seeded with ‘Bullseye’ tall fescue (Festuca arundinacea Schreb.). Treatments included 49 and 73.5 kg·ha−1 of nitrogen (N) without P, 49 kg·ha−1 of N plus three different rates of P (24.5, 49, and 73.5 kg·ha−1), and a nonfertilized control. Comparisons between groups that received treatment with 49 kg·ha−1 of N without P and treatments with 49 kg·ha−1 N with P revealed few significant groundcover responses to the addition of P. Of 12 groundcover assessments performed during four experiments, contrasts revealed only one instance of a higher percentage of groundcover in response to the addition of P. This occurred during an experiment having a pretreatment Mehlich-3 P level of 38 mg·kg−1. Comparisons indicated greater clipping yields in response to the addition of P in one of the four experiments. This occurred in soil that was core-aerated and sliced with an initial Mehlich-3 P level of 66 mg·kg−1. In most cases, Mehlich-3 P levels at the end of each experiment increased as the P application rates increased. The only instance in which comparisons between treatment with 49 kg·ha−1 N without P and treatments with 49 kg·ha−1 N with P demonstrated a significant leaf tissue response to P during the experiment with soil that was core-aerated and sliced with a pretreatment Mehlich-3 P level of 66 mg·kg−1. When individual treatments were compared, the 73.5 kg·ha−1 N treatment without P produced similar or higher groundcover and clipping yields than all other treatments during all four experiments. This study revealed few groundcover and variable tall fescue clipping yield responses to P additions when applied at rates used for starter fertilizer applications on silt loam soil during late summer and fall. Groundcover and growth responses due to P in starter fertilizers do not appear to be solely related to soil test P levels, and other factors such as the method of establishment (tilling soil vs. core-aerating and slicing the soil surface), environmental conditions, and the N content of soil may be involved.

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Trygve S. Aamlid and Peter J. Landschoot

Spent mushroom substrate (SMS) is used by the turf industry in the northeastern United States for soil improvement. When tilled into soil at high rates, some turfgrass managers claim that SMS inhibits turf seed germination. The authors’ objectives were 1) to determine whether fresh SMS inhibits turf seed germination and, if so, which species are most adversely affected; 2) to evaluate whether any inhibition incited by SMS is the result of osmotic effects or toxicity of compounds in SMS extracts; 3) to determine whether any negative effect of SMS on germination can be eliminated by leaching the SMS-amended soil before seeding; and 4) to assess the performance of SMS on seedling emergence in the field. Germination of nine turfgrass species was evaluated in mixtures made from fresh SMS (electrical conductivity of saturated paste extract = 11.9 dS·m−1) and a loamy sand soil. Germination inhibition resulting from SMS was most pronounced in the following order: Colonial bentgrass (Agrostis capillaris L.) > sheep fescue [Festuca ovina L. ssp. hirtula (Hackel ex Travis) Wilkinson] > Kentucky bluegrass (Poa pratensis L.) > hard fescue [Festuca trachyphylla (Hackel) Krajina] > creeping bentgrass (Agrostis stolonifera L.) > chewings fescue [Festuca rubra L. sp. commutata (Thuill.) Nyman] = strong creeping red fescue (Festuca rubra L. ssp. rubra Gaud.) > slender creeping red fescue [Festuca rubra L. sp. litoralis (Meyer) Auquier] > perennial ryegrass (Lolium perenne L.). SMS had a stronger negative effect on germination rates than on final germination percentages. Germination of perennial ryegrass and Kentucky bluegrass on blotter paper moistened with SMS extracts or polyethylene glycol of equivalent osmotic potentials showed that the inhibition was primarily the result of osmotic effects. In an experiment with a 50% soil/50% SMS (v/v) mixture, Kentucky bluegrass germinated better in pots that had been watered with 133% or 167% of the evaporation rate for 10 days prior to seeding than in unleached pots. Although the negative effect of SMS on seed germination was not confirmed in a field study in which ECe values never exceeded 4.1 dS·m−1, the authors conclude that incorporation of high rates of SMS represents a potential problem for turfgrass establishment.

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Peter J. Landschoot and Charles F. Mancino

This study was conducted to determine: 1) if the Minolta CR-310 Chroma Meter can detect color differences among bentgrass (Agrostis stolonifera L., A. capillaris L.) cultivars maintained as a turf; 2) how the CR-310 parameters of hue angle, lightness, and chroma compare with visual color assessments; and 3) if the CR-310 can provide consistent color measurements among evaluators. Differences were detected among cultivars with respect to hue angle, lightness, and chroma. Hue angle and chroma were significantly correlated with visual color assessments when data were averaged across all evaluators. Lightness was not strongly associated with visual color assessment. Differences were found among evaluators for visual color assessment, lightness, and chroma, but not for hue angle measurements. Thus, hue angle appears to be the most consistent CR-310 parameter for measuring color of bentgrass turf. These results indicate that the CR-310 can be used to evaluate the color of bentgrass cultivars maintained as a turf and provides consistent hue angle measurements among evaluators, regardless of experience in rating turf color. The CR-310 is probably best used for measuring relative color differences and may be useful if cultivars of similar color are desired in blended turfs.

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Yu Huang, John E. Kaminski and Peter J. Landschoot

Dollar spot, caused by Sclerotinia homoeocarpa F.T. Bennett, is an important disease of creeping bentgrass (Agrostis stolonifera L.) on golf courses in the northern United States. Canopy moisture in the form of dew plays an important role in the development of dollar spot and routine displacement has been shown to reduce disease severity. The use of plant growth regulators (PGRs) is a common management practice for maintaining creeping bentgrass fairways, but their influence on dollar spot is unclear. The objective of this field study was to elucidate the influence of dew removal at the time of fungicide application on dollar spot control in creeping bentgrass regulated by trinexapac-ethyl (TE). Main factors in the study included three dew removal strategies (non-treated, dew removed–mowed, and dew removed–not mowed) before the application of four fungicide treatments (non-treated, chlorothalonil, propiconazole, and iprodione). All fungicide treatments were applied once to turfgrass previously treated with TE or not treated. The presence or absence of dew at the time of fungicide application generally had no influence on fungicide performance with respect to dollar spot control. Based on the results of this study, dew removal before the application of fungicides targeting dollar spot is unnecessary. Applications of TE before fungicides reduced dollar spot severity in some cases, but reductions in symptom expression were limited and did not result in markedly improved dollar spot control.

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Eric M. Lyons, Peter J. Landschoot and David R. Huff

Little knowledge exists regarding root distribution of creeping bentgrass (Agrostis stolonifera) and annual bluegrass (Poa annua) in root zones of golf course putting greens. To compare root distribution between these species, three experimental cultivars of greens-type annual bluegrass and two commercial cultivars of creeping bentgrass (‘Penncross’ and ‘Penn A-4’) were established on an experimental golf green and managed under two nitrogen (N) fertility levels (195 and 65 kg N/ha/year) over a 2-year period. Creeping bentgrass had two and three times the total root mass compared with annual bluegrass during the first and second years of the experiment, respectively. At soil depths of 3–12 cm and below 12 cm, creeping bentgrass had three to four times the root mass compared with annual bluegrass at various times during the experiment. During the first year of the experiment, both species exhibited greater than 50% decrease in total root mass from June to August. During the second year, creeping bentgrass total root mass decreased 10% to 15% and annual bluegrass total root mass decreased 25% to 30% over the same period. Of the two bentgrasses, ‘Penn A-4’ creeping bentgrass exhibited greater total root mass only in the second year; however, ‘Penn A-4’ exhibited greater root mass than ‘Penncross’ below 12 cm in both years. Creeping bentgrass cultivars showed greater root mass below 12 cm at 65 kg N/ha/year compared with 195 kg N/ha/year on some sampling dates in both years. Annual bluegrass cultivars showed no change in any root mass parameters in response to N rates (data not shown), but specific root length (SRL) of annual bluegrass increased under the 65 kg N/ha/year rate compared with the 195 kg N/ha/year rate, whereas SRL of creeping bentgrass was similar at both N rates. Tiller densities of both species increased under the 195 kg N/ha/year rate. ‘Penn A-4’ exhibited higher tiller densities than ‘Penncross’ throughout the experiment and at times was equivalent to the tiller densities of the annual bluegrass cultivars. These results suggest that although creeping bentgrass increases root mass deeper in a putting green root zone mix at lower N rates (65 kg N/ha/year), annual bluegrass exhibits plasticity in specific root length in response to different N rates.

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Peter J. Landschoot, Bradley S. Park, Andrew S. McNitt and Michael A. Fidanza

Fumigation of annual bluegrass (Poa annua L.)-infested putting greens before seeding creeping bentgrass (Agrostis stolonifera L.) prevents stand contamination due to annual bluegrass seedling emergence. Dazomet is a soil fumigant labeled for use in putting green renovation; however, limited data are available on efficacy of dazomet controlling annual bluegrass seedling emergence following surface-applications. The objectives of this study were to determine the influence of rate and plastic covering of surface-applied dazomet on annual bluegrass seedling emergence in putting green turf; and safe creeping bentgrass seeding intervals following applications of dazomet to putting green surfaces. Treatments were applied in late summer to the surface of a 20-year-old stand of turf maintained as a putting green and plots were watered immediately after application and throughout each test period. Plastic-covered dazomet treatments had fewer annual bluegrass seedlings than noncovered dazomet treatments. Three plastic-covered dazomet treatments (291, 340, and 388 kg·ha-1) provided complete control of annual bluegrass seedlings during 2000 and 2001. None of the noncovered dazomet treatments provided complete control of annual bluegrass seedling emergence. Results of the seeding interval experiment revealed that creeping bentgrass seedling development was not inhibited in both plastic-covered and noncovered dazomet treatments, when seeded 8, 10, 13, and 16 d after dazomet was applied to the turf surface. Results of this study demonstrate that dazomet, applied at rates ≥291 kg·ha-1 to the surface of a putting green in summer and covered with plastic for 7 d, can control annual bluegrass seedling emergence. Chemical name used: tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione (dazomet).