Seed germination and vegetative growth studies were conducted to determine relative salinity tolerance of greens‐type Poa annua L. compared with other cool‐season turfgrass species. Effects of increasing salinity stress on final germination percentage (FGP), germination rate (GR), clipping yield dry weight (CYD), verdure dry weight (VD), root dry weight (RD), and the longest root length (LRL) were evaluated for nine experimental lines of greens‐type P. annua, two cultivars of Kentucky bluegrass (P. pratensis L.), three cultivars of creeping bentgrass (Agrostis stolonifera L.), and one cultivar of perennial ryegrass (Lolium perenne L.). Generally, FGP, GR, CYD, VD, and RD declined with increasing salinity; LRL increased at lower salinity levels but decreased at higher levels. Perennial ryegrass ‘Charger II’ and creeping bentgrass ‘Mariner’ exhibited the most salinity tolerance while Kentucky bluegrass cultivars exhibited the least. Salinity tolerance of greens‐type P. annua was intermediate; however, some experimental lines exhibited nearly equal salinity tolerance to that of Mariner. Our data suggest greens‐type P. annua possesses moderate to good salinity tolerance during seed germination and vegetative growth relative to other cool‐season turfgrass species and has potential to be used on golf courses with moderate salt problems affecting turf establishment and maintenance.

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Abstract:Fairy ring is a common disease of turfgrasses worldwide, and necrotic or severely injured turfgrass and soil water repellency are frequently observed in those turfgrass sites exhibiting type-I fairy ring symptoms. The objective of this research was to evaluate soil chemical and physical properties associated with type-I fairy ring symptoms in turfgrass. Soil samples were obtained from type-I fairy ring symptoms on two golf course fairways and one lawn area. Soil analysis from all the three locations revealed concentrations of ammonium-nitrogen, potassium, and sulphur were statistically higher in soil underlying necrotic or bare zones versus soil in healthy turfgrass zones. Soil electrical conductivity (EC) also was higher, while volumetric soil water content was consistently lower in necrotic zones versus soil under healthy turfgrass. Soil water repellency was considered moderate to severe in necrotic zones and mostly wettable to subcritical repellency in soil underlying healthy turfgrass. Soil pH, total nitrogen, magnesium, calcium, cation exchange capacity (CEC), and organic matter content (OM) levels were not consistently different among necrotic and healthy turfgrass zones. The necrotic zones of those type-I fairy ring areas in turfgrass were most likely associated with a combination of direct and indirect effects of the basidiomycete fungi on soil hydrophobicity and the accumulation of potentially phytotoxic compounds in the turfgrass root zone. Further research is needed to explore the interaction of basidiomycete fungi and the soil chemical and physical environment on turfgrass, and evaluate practices and strategies to control type-I fairy ring symptoms in turfgrass.

Cultivar selection and nitrogen (N) fertility signi®cantly in¯u-ence the performance of creeping bentgrass (Agrostis palustris Huds.) in warmer regions of the United States. This study was conducted to determine the effects of N on root and shoot growth of three creeping bentgrass cultivars. The effect of three N rates (195.3, 390.6, and 586.0 kg Naha year) on the total root length density (TRLD), deep root length density (DRLD), visual shoot quality, shoot density, and root to shoot ratio (RSR) of Crenshaw',`L93', and`Penncross' creeping bentgrass were evaluated in the University of Georgia Rhizotron at Athens, GA. Over the 19 month study, cultivar type and N rate signi®cantly affected root and shoot growth with slight interaction. Crenshaw and L93 showed greater TRLD, DRLD, and visual shoot quality than Penncross at the 390.6 kg N rate. RSR was signi®cantly JOURNAL OF PLANT NUTRITION, 24(3), 535±548 (2001) 535 in¯uenced by N rate but not cultivar type. Both L93 and Crenshaw possessed signi®cantly higher RSR at the 195.3 kg N rate than the 586.0 kg N rate.

Pythium aphanidermatum and other Pythium spp. cause Pythium blight of turfgrasses in the United States. Phosphonate fungicides suppress Pythium blight when applied preventatively, but efficacy may vary with product, rate and timing of application, and host species. The objectives of this study were to assess the inhibitory effects of phosphorous acid on Pythium spp. in vitro, and determine if active ingredient and formulation of phosphonate fungicides provide similar levels of Pythium blight suppression on perennial ryegrass and creeping bentgrass when applied at equivalent rates of phosphorous acid. Phosphorous acid EC50 values (effective concentration that reduces mycelial growth by 50%) for P. aphanidermatum isolates ranged from 35.6 to 171.8 μg/ml. EC50 values for isolates of six other Pythium spp. were between 38.7 and 220.8 μg/ml. In 2004 and 2005, all phosphonate treatments provided significant suppression of Pythium blight symptoms on creeping bentgrass and perennial ryegrass relative to the untreated control. No differences in percentage of blighted turf occurred among phosphonate treatments when applied at equivalent rates of phosphorous acid in either year of the study, regardless of active ingredient, formulation, or turfgrass species.

Of the essential nutrients, N fertility generally influences golf course putting green (PG) quality and growth rate most significantly. Despite considerable field research on N fertility of PGs, results interpretation and transfer to practice is complicated by various influential factors; including unrepresentative mowing heights and/or frequency, varying irrigation water quality, undeclared composition of mixed swards, withdrawn cultivars, and/or use of temperature-dependent organic fertilizer sources. A 2-yr field study was initiated in 2003 at University Park, PA, to evaluate the influence of soluble N fertilizer source and rate on qualitative and nutritional parameters of a mature, primarily surface-drained, "push-up" PG cohabited by 'Penn A4' creeping bentgrass (Agrostis palustris Huds.) and annual bluegrass (Poa annua L.). Using an array of soluble N form quotients (NH 4-N/ NO 3-N), split applications of annual N fertilizer rates ranging from 69 to 402 kg ha 21 were sprayed every 15 6 4 d, April to October. Putting green growth, color, N uptake (NUP), and leaf N, K, Ca, Mn, Cu, and Zn increased directly with N rate, while plots receiving N rates in excess of 244 kg ha 21 yr 21 demonstrated acceptable PG quality and tissue nutrient concentrations. However, N rates .244 kg ha 21 yr 21 containing .50% NH 4-N significantly enhanced shoot growth, color, NUP, leaf Mn, P, and Mg levels, when compared to equal rates containing $50% NO 3-N. Frequent fertilization with NH 4-N at annual rates .244 kg ha 21 maximized canopy color and most tissue nutrient levels of a mature creeping bentgrass/annual bluegrass cohabited PG growing on a neutral, fine-textured soil.

Proactive optimization of soil chemistry is a task commonly overlooked by agronomic practitioners. Agricultural field assessments have reported depletion of extractable soil silicon (Si) from shallow depths of intensively managed systems. While not recognized as a plant-essential nutrient, Si accumulates in epidermal and vascular tissue of grass leaves, sheaths, and shoots. A field study of Ca/Mg-silicate (SiO3) pelletized soil conditioner was initiated on a perennial ryegrass (Lolium perenne L. cvs. 1:1:1 Manhattan, Brightstar SLT, Mach 1) athletic field in 2010. Plots were trafficked by a wear simulator weekly, June through Sept. in 2011 and 2012. Canopy quality measures, clipping yield, tissue composition, soil pH, and plant-available soil Si levels were regularly collected over the two-year study. Under intense wear treatment (traffic), perennial ryegrass plots treated annually by granular application of 1220 or 2440 kg Ca/Mg-silicates per hectare showed significantly improved mean canopy density relative to plots receiving equal Ca and Mg as lime. These described Ca/Mg-SiO3 annual application rates coincided with acetic acid extractable soil Si levels > 70 mg kg−1 in the 0- to 8-cm soil depth. Experimental and temporal variability preclude reporting of a critical threshold concentration of leaf Si for improved perennial ryegrass wear tolerance. Future efforts towards this end should sample tissue of plots receiving wear treatment, rather than adjacent, non-worn proxies.

Current literature suggests Poa annua L. (annual bluegrass) is intolerant to salinity stress. Response of greens‐type Poa annua to chronic salinity stress (12 wk at 8.0 dS m−1) was evaluated over two greenhouse experiments. Vegetative samples of 33 greens‐type P. annua experimental lines were maintained at a 6.4‐mm mowing height and irrigated daily with modified Hoagland's solutions possessing salinity levels of 0.7 dS m−1 (nonsaline control) or 8.0 dS m−1 (NaCl treatment, approaching 0.25 strength sea water, approx. 13.5 dS m−1). Clipping yield dry weight (CYD) and leaf water content (LWC) were measured weekly. Digital images were collected at the end of weeks 1, 4, 8, and 12 to determine percentage cover (PC) and dark green color index (DGCI). Across all lines, all sample dates, and both experiments, salinity stress significantly reduced PC (30.8%), DGCI (9.3%), CYD (33.9%), and LWC (3.3%) compared with nonsaline controls (α = 0.05), suggesting chronic salinity stress is detrimental to greens‐type P. annua quality. However, significant differences in relative PC and relative CYD were observed among lines, indicating that substantial variation in salinity tolerance exists in greens‐type P. annua. Numerous greens‐types P. annua experimental lines, such as PSU 99‐9‐21, PSU 01‐1‐46, and PSU 05‐1‐14, possess moderate‐to‐good salinity tolerance and are potentially suitable for use on golf courses with moderate salt problems.