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Article Excerpt
GOLF COURSES may represent a significant environmental issue because of the potential for ground water contamination by N[O.sub.3.sup.-] from fertilizers (Petrovic, 1990). Putting greens are of particular concern because the root zone is often made of high-porosity sand mixtures to prevent compaction and water logging. Sandbased root zones have little capacity to retain nutrients or water, and frequent N applications and irrigations are required (Brown et al., 1982; Bigelow et al., 2001). Under these conditions, N[O.sub.3.sup.-] leaching can be high (Brown et al., 1982; Mancino and Troll, 1990; Shuman, 2001).
Management factors known to affect N[O.sub.3.sup.-] leaching under golf green conditions include irrigation volume, application rate and timing, and source of N fertilizers (Petrovic, 1990). Management practices need to optimize N uptake by turfgrasses to reduce the risk of N[O.sub.3.sup.-] leaching. Petrovic (1990) reported N uptake ranging from 5 to 74% of applied N. Differences in N uptake and utilization as well as differences in N leaching patterns have been reported among turfgrass species and cultivars (Cisar et al., 1989; Liu et al., 1997; Jiang and Hull, 1998; Jiang et al., 2000; Bowman et al., 2002). Some of the variations in N uptake efficiency may be due to morphological and physiological differences among grasses (Carrow et al., 2001). The morphology and the depth of root development appear to be important factors affecting N uptake (Bowman et al., 1998; Sullivan et al., 2000).
In Canada, creeping bentgrass (A. stolonifera L.) and annual bluegrass are cultivated on 53 and 36% of the golf greens, respectively (Royal Canadian Golf Association, 2003). However, little is known about N uptake efficiency and N leaching under golf greens cultivated with bentgrass or annual bluegrass. The objective of this research was to compare, in a greenhouse experiment, N uptake and potential mineral N leaching among various annual bluegrass ecotypes and bentgrass species grown in lysimeter columns simulating a golf-green profile.
MATERIALS AND METHODS
A lysimeter experiment was conducted in a greenhouse at the Univ. of Guelph, Guelph, ON, Canada. During the 57-d experimental period (October to December 2002), air and root zone temperatures were monitored with a data logger (HOBO, PRO series, Onset Computer Corporation, Bourne, MA). The mean daily air and root zone temperatures at the 5-cm depth were 22.8 [+ or -] 2.1[degrees]C and 17.0 [+ or -] 0.6[degrees]C, respectively. The photoperiod was 16 h [d.sup.-1] with supplemental high-pressure sodium lighting (PAR, 80 [micro]mol [m.sup.-2] [s.sup.-1]) for the duration of the experiment.
Plant Material and Culture
The plant material consisted of 11 annual bluegrass ecotypes and three bentgrass species. Six annual bluegrass ecotypes were grown from tillers selected from golf greens, at different geographical locations, on the basis of their potentially superior turf characteristics. Three ecotypes were selected in the province of Quebec, Canada (Bic, Quebec City, and Montebello; mean annual temperature, 4.7[degrees]C; mean annual precipitation, 1011 mm), and three were selected in the Guelph area in Ontario, Canada (mean annual temperature, 6.5[degrees]C; mean annual precipitation, 769 mm). Finally, five USA ecotypes were selected from tillers grown for 6 wk from seeds planted in 10-cm-diam. pots containing sand-peat root zone mixture. The seeds were provided by Dr. David Huff (Pennsylvania State Univ.) and the ecotypes were originally collected in the Mid-East region of the USA (mean annual temperature, 9.5[degrees]C; mean annual precipitation, 813 mm).
The bentgrass species were creeping bentgrass ('Penncross' and 'Penn-A4'), dryland bentgrass (A. castellana Boiss. & Reut. cv. 'Highland'), and velvet bentgrass (A. canina L. cv. 'Vesper'). As with the USA annual bluegrass ecotypes, the bentgrasses were selected from tillers grown from commercial seeds planted in 10-cm-diam. pots for a 6-wk period.
All individual tillers were transplanted into 3.8-cm-diam., 14.0-cm-high cylindrical containers (conetainers, RL C7 Stuby Cell, Stuewe and Sons, Inc., Corvallis, OR) filled with a 80:20 sand-peat mix (v/v) and were grown in a greenhouse. Plants were irrigated as needed, fertilized twice a week (20-8-20; 250 mg N [L.sup.-1], Plant-Prod, Plant Products Co. Ltd., Brampton, ON, Canada) and clipped weekly with scissors to approximately 1 cm.
Lysimeter Columns and Plant Establishment
Lysimeters were constructed using opaque polyvinyl chloride columns (10-cm diam., 40-cm depth). A cone collector was sealed to the bottom of each lysimeter and was connected to a 500-mL bottle by a tygon tube. The cone collector section of each lysimeter was filled with 10 cm...
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