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.
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.
Depletion of extractable silicon (Si) from surface soil depths has been observed in managed production systems. While not characterized as a plant essential nutrient, Si accrues in epidermal and vascular tissue of monocotyledonous plants. A field evaluation of granular Ca/Mg-rich liming agents was initiated on a creeping bentgrass (Agrostis stolonifera L. cv. Declaration) fairway in 2010. Excluding the control, treatments comprised 2440 kg (ha year) −1 topdressing of calcitic/dolomitic blended limestone or Ca/Mg-SiO 3 in semi-annual or more frequent "split" applications. Each week of the 2011 and 2012 growing seasons, a dedicated wear simulator trafficked the fairway plots. Measures of canopy quality, clipping yield, tissue composition, soil pH, and plant-available soil Si levels were collected frequently. The described Ca/Mg-SiO 3 annual topdressing rates correlated with acetic acid extractable Si levels >30 mg kg −1 in the 0-to 5-cm soil depth. Neither creeping bentgrass vigor, nutrition, nor leaf water content was influenced by significantly elevated levels of soil and tissue Si. Relative to non-trafficked plots, all split plots within trafficked main plots showed similarly reduced canopy quality regardless of topdressing treatment. If a critical threshold leaf Si concentration for creeping bentgrass wear tolerance enhancement exists, it is unlikely <11 g Si kg −1 .
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