Turfgrass managers regularly apply K to creeping bentgrass [Agrostis stolonifera var. palustris (Huds.) Farw.] putting greens on the basis of soil test results or in some relation to annual N fertilizer rates. In the many putting greens that have sand rootzones, K is susceptible to leaching, and in calcareous sands, K availability is further limited by high Ca levels. The K requirements for calcareous sand putting greens are not clear. A 2-yr field study was conducted on an L-93 creeping bentgrass putting green grown on a calcareous sand rootzone at Ithaca, NY. Potassium fertilizer was applied with N in 167 mL H 2 O m 22 at 0, 1, 2, 3, 5, and 6 g K m 22 14 d 21 during the 2002 and 2003 growing seasons. Leaf tissue samples were collected monthly, and soil samples were collected every 56 d. Turfgrass performance characteristics such as color, quality, and ball roll were evaluated visually and quantitatively. Without K addition, soil test K indicators decreased over time, and low levels of soil K (,1.25 mmol 1 M NH 4 OAc-K kg 21 ) were prevalent in all plots receiving the lowest (,2 g K m 22 14 d 21 ) K rates. Potassium application had no beneficial effects on turfgrass performance. We conclude that acceptable creeping bentgrass performance can be achieved across a wide gradient of soil K levels and tissue K contents (255-639 mmol kg 21 dry weight) in calcareous sand rootzones. Recommended levels of soil and tissue K should be reevaluated to avoid gratuitous use of K fertilizers.

Control of goosegrass is difficult in the pan-Pacific region. No herbicides are currently labeled for selective control of goosegrass in seashore paspalum turf, a species used regularly on golf courses throughout the tropics. Sequential granular applications of sodium chloride (99% sodium chloride, 1% sodium silicoaluminate, 83% 0.5 to 0.25 mm diam) at 488 kg/ha did not effectively (> 70%) control goosegrass in this study. Goosegrass injury following sequential granular applications of sodium chloride, at 488 kg/ha, subsided at 6 wk after initial treatment (WAIT). A single application of MSMA at 2.40 kg/ha plus metribuzin at 0.56 kg/ha provided 96 and 83% control of goosegrass 8 WAIT in 2007 and 2008, respectively. Sequential applications of MSMA plus metribuzin at lower rates yielded similar results. Applications of foramsulfuron did not effectively control (> 70%) goosegrass in this study, suggesting a possible tolerance to this treatment. Applications of MSMA plus metribuzin controlled goosegrass (> 70%), but induced phytotoxic injury to seashore paspalum turf. Additional research is needed to evaluate strategies for POST control of goosegrass in seashore paspalum turf that do not induce phytotoxic turfgrass injury after application.

Sourgrass is a stoloniferous perennial grassy weed found on golf courses throughout Hawaii. No herbicides are currently labeled for selective control of sourgrass in seashore paspalum turf, a species used regularly on golf courses throughout the tropics. A single granular application of fine salt (99% sodium chloride, 1% sodium silicoaluminate, 83% of particles 0.5 to 0.25 mm in diameter) at a rate of 1,464 kg/ha provided 84 and 23% control of sourgrass 6 wk after initial treatment (WAIT) in 2007 and 2008, respectively. Sequential granular applications of fine salt at 488 kg/ha provided 92 and 96% control of sourgrass in 2007 and 2008, respectively, at 6 WAIT. Granular applications of a coarse salt (100% sodium chloride, 75% of particles 2.0 to 1.0 mm in diameter) provided a lower level of control than fine salt at both the 1,464- and 488-kg/ha rates on three out of four rating dates in 2008; a similar trend was observed in 2007, but no significant differences were observed between these treatments. All salt treatments led to higher soil sodium adsorption ratios (SAR) and electrical conductivity (ECe) than the untreated check; however, levels reported in this study were significantly lower than the threshold SAR and ECelevels that have been associated with reduced seashore paspalum growth. Sequential applications of MSMA at 1.12 kg/ha and MSMA plus metribuzin at 1.12 kg/ha and 0.28 kg/ha, respectively, provided greater than 90% control in 2008, but less than 40% control in 2007. Greater seashore paspalum injury was observed following applications of MSMA and MSMA plus metribuzin than following salt applications. Additional research is needed to evaluate strategies for controlling sourgrass in seashore paspalum turf that do not induce phytotoxic injury after application.

No abstract

Conventional soil nutrient guidelines are higher than needed to produce high quality turfgrass. Although there have been repeated calls for more turfgrass soil calibration research, it is not practical to conduct conventional soil test calibrations for this global crop. Turfgrass comprises more than 10 common species and hundreds of cultivars, grown in a multitude of soils and climates. We took an indirect approach to identify universally applicable guidelines by studying a large sample of 16,163 Mehlich 3 soil test results collected from good-performing turf. We modeled a subset (n = 3,683) of those results, specifically from soils with low nutrient holding capacity, as 2 parameter log-logistic distributions. We take these continuous probability distributions to be representative of soils in which good-performing turf is being produced. The minimum levels for sustainable nutrition (MLSN) guidelines were selected as the value \(x\) at which the probability of a random sample \(X\) drawn from the distribution being less than or equal to \(x\) is \( 0.1\). That is, we identified the level \(x\) where \(P (X ≤ x) = 0.1\). We propose the MLSN guidelines as minimum levels for all turfgrass sites, with fertilizer recommendations suggested as the quantity sufficient to prevent each element from dropping below the MLSN guideline. The MLSN guidelines from the Mehlich 3 data used in this paper are, for K, P, Ca, Mg, and S respectively, 37, 21, 348, 47, and 7 mg kg-1.