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Foliar fertilization is an increasingly popular method of ensuring golf course putting green nitrogen (N) sufficiency in season. The low cost, high N-content, and favorable handling characteristics of urea (46-0-0) make it a common N-source in foliar treatments of horticultural crops. While numerous investigations confirm incomplete recovery of foliarly-applied urea-N by turfgrass, few field assessments of NH3 volatilization from greens have been conducted. Meanwhile, NH3 emissions reduce air quality and contribute to non-point nutrient loading of water resources. The research objectives were to (i) develop a method for field-implementation of closed dynamic/flux chambers to measure NH3 volatilization from 0 to 24 h following foliar application of urea-N to putting greens; and (ii) infer the significance of flux chamber NH3-N volatilization measures relative to levels arising from simultaneous static-chamber measures. Creeping bentgrass ( Agrostis stolonifera L. 'Penn G-2') putting greens were foliarly treated by 20-44 kg urea-N ha−1 from 2013 to 2015, and NH3 volatilization measured using H3BO3 trap-equipped flux and/or static chamber systems. Flux chamber measures of NH3 volatilization accounted for 7.1% of the urea-N fertilizer applied 24 h previous. Simultaneous static chamber measures of NH3 volatilization were an order of magnitude less. A replicated flux chamber trapping efficiency trial showed 63% mean NH3 recovery. Thus under the duration and conditions described, 7.1-11.2% of foliar urea-N applications can be expected to volatilize from putting greens. Regarding closed chamber system measurement of NH3 volatilization from small field plots, the described flux chambers afford applied scientists a more precise and efficient method than static chambers. [ABSTRACT FROM AUTHOR]

Considering the vast number of golf course putting greens (PGs) comprised of creeping bentgrass (Agrostis stolonifera L.) and annual bluegrass (Poa annua L.) polystands; greater understanding of seasonal growth response to fall applications of growth regulators and/or N fertilizers is needed. The objective was to determine how timing of fall trinexapac-ethyl (TE; 4-[Cyclopropyl-a-hydroxymethylene]-3,5-dioxo-cyclohexanecarboxylic acid ethyl ester) plant growth regulator and/or N application rate influence(s) PG N assimilation, removal, and spring canopy density. Field studies were initiated on a mixed creeping bentgrass + annual bluegrass PG in September 2009 or 2010. Foliar applications of TE at 0, 0.044+0.044, or 0.088 kg ha-1 were made in combination with soluble N at 30 or 60 kg ha-1. Treatment initiations, recurring every 10±1 d and centered on 15 October (30-yr average date of first frost), represent the four treatment timings. Fall N rate directly influenced PG density but did not interact with TE. Compared to the 30 kg ha-1 N rate, significantly lesser proportions of the 60 kg N rate were removed by mowing. Fall and early-spring PG growth decreased linearly with later N application dates, yet application timing significantly interacted with TE. Late fall TE treatment reduced early-spring shoot growth as much as 20%. [ABSTRACT FROM AUTHOR]

Within the range of environmental conditions for which creeping bentgrass (Agrostis stolonifera L.) is adapted, cultural management significantly influences golf course putting green (PG) growth and quality. The experimental objective was to identify PG quality and growth response to rate, type, and/or timing of foliarly-applied N fertilizer. In 2009 and 2010, three independent fertility trials were conducted on a sand-based PG established to a 1:1 blend of Penn A-l and Penn A-4 creeping bentgrass. Excepting the zero-N control, treatments were prepared using amine or salt 15-0-7 liquid fertilizer comprising wholly-soluble nutrient forms and applied at 24.5+24.5, 37, or 49 kg N ha-1. Clipp ing yields were collected weekly and digested for N content. Canopy reflectance was used to calculate normalized differential vegetative (NDVI) and dark green color (DGCI) indices. Nitrogen rate directly influenced PG mean NDVI, DGCI, clipping yield, and N removal. Likewise, the amine supported greater mean PG quality than the salt fertilizer. Availability of fertilizer, estimated by PG growth and N removal rate, declined dramatically over the 6-wk experiments. Initial PG growth response to the single 49-kg N application significantly exceeded the 24.5+24.5 kg N "split" application. However, beneficial response to split applications, relative to the single 49 kg N treatment, was observed in latter weeks. While commercially-available liquid fertilizers vary in their suitability, managers are recommended to employ a <15-d reapplication interval in meeting the 15 to 49 kg N ha-1 monthly creeping bentgrass PG requirement. [ABSTRACT FROM AUTHOR]

The profound impact of soil water repellency (WR) on vadose zone processes makes accurate characterization of this phenomenon paramount. Numerous WR measurement techniques exist, each having advantages and disadvantages with regard to laboriousness, resolution, and accuracy. The molarity of ethanol droplet (MED) test quantifies WR as the lowest ethanol concentration permitting droplet penetration within 5 s, or alternatively, the 90° liquid surface tension of the infiltrating droplet (γND). This method is simple and rapid but poorly represents soil wetting behavior across measurement intervals. Although time consuming, water/ethanol sorptivity ratio calculation of the repellency index (R) generates a continuous, linear scale of WR that intrinsically isolates the effect of WR on infiltration. This study compared MED and R measurements of sand samples displaying varying degrees of WR. Each technique was performed at 20°C and 1.78 kPa H2O vapor pressure using duplicate subsamples of oven-dried (55°C) sands. A nonlinear association between R and γND or MED was observed. Regressing log10 R by γND revealed a statistically significant model, yet the 95% log10 R prediction interval included values less than the theoretical lower limit of R. Alternatively, regressing log10 R by MED generated the following model (P < 0.0001, r² = 0.727): log10 R = 0.705 + 0.5144(MED), capable of predicting R within the operation bounds of R theory. While the predicted R values are distributed across a wide interval, their availability offers cautious users an intuitive scale for enhanced interpretation of more commonly generated MED data. [ABSTRACT FROM AUTHOR]

Particulate organic matter (OM) and surface area-limited sands are associated with soil water repellency (SWR) in turfgrass systems. The increasing ubiquity of amended sand rootzones warrants investigation of factors contributing to SWR. Our objective was to identify how amendment type and/or inclusion rate affect rootzone SWR over a range of irrigation regimes. A U.S. Golf Association-specified sand was amended with dried turfgrass roots and either sphagnum peat moss (SPM), reed sedge peat (RSP), biosolid compost (BSC), or calcined clay (CC) at 0, 0.1, or 0.2 m³ m-3. Mixes were saturated, gravitationally drained, incubated under isothermal ventilation having mean vapor pressures of 1.78, 2.19, or 2.45 kPa, and reirrigated when matric tension exceeded 300 kPa. After 138 d, rootzone subsamples were eluted of particulate OM before measuring mineral-adsorbed hydrocarbon content (MAHC) by infrared spectroscopy. The repellency index was used to quantify SWR of intact (Rintact) and eluted (Reluted) samples. Amendment rate (0.2 > 0.1 > 0 m³ m-3) and type (BSC> RSP = SPM > CC) significantly affected Rintact. Only CC-amended rootzones were more wettable than the control. Severely elevated Reluted and MAHC were observed in all sands amended by BSC. Inclusion of SPM or ASP at 0.1 m³ m-3 resulted in Reluted and MAHC values statistically equivalent to the control rootzone. At 0.2 m³ m-3 inclusion, all organic amendments significantly increased Reluted and MAHC relative to the control (BSC> RSP = SPM). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]