Spatial and temporal variation of soil, climate, plants and irrigation requirements are challenges for modern agriculture and complex turfgrass sites. Precision agriculture (PA) evolved to improve site-specific management based on obtaining site-specific information. The focus of this concept paper is on the emerging area of precision turfgrass management (PTM) with attention given to: (a) comparing the concepts of PTM and PA in terms of driving forces and challenges that must be addressed for PTM to progress in science and practice and (b) discussion of specific field mapping applications (purposes) for different turfgrass situations such as golf courses, sod production fields and sports fields. The field applications relate to site-specific management of irrigation, salinity, fertilizer application and cultivation. To illustrate the potential for PTM, different approaches that may be necessary for PTM compared to PA are discussed. The initial factor that hindered the adoption of PTM has been the lack of mobile sensor platforms that can determine both key soil and plant properties for turfgrass situations. This paper concentrates on PTM field applications that involve mapping of both soil and plant attributes, in contrast to only optical sensing mapping.

This paper presents the first micrometeorological-based measurements of methane (CH4) emissions from Asian rice paddies of which we are aware. The research features the tunable diode laser trace gas analyzer system (TGAS) recently developed at the University of Guelph. CH 4 fluxes were measured between March 9 and 24, 1992, from an irrigated rice paddy field at the International Rice Research Institute (IRRI), the Philippines. The daytime CH 4 flux averaged 6.0/xg m -2 s -1 . The CH 4 fluxes displayed a diurnal trend similar to daily soil temperature curves, with peak emissions of about 8/xg m -2 s -1 in the early afternoon. A tenfold increase in CH 4 emissions (to about 70/xg m -2 s -1) during a brief weeding experiment resulted from soil disturbance. Up to 25/xg m -2 s -1 of CH 4 were released during a drying of the field, after which unsuitable soil redox potentials apparently suppressed methanogenesis. The CH 4 flux was also arrested when the field was flooded with oxygen-rich water during a heavy rainstorm. where Fme flux of CH 4 (/xg m -2 s-l); K eddy diffusivity (m2 s -•); ACme change in CH 4 concentration (/xg m-3); Az (m) vertical height difference. TGAS measurements were used to determine a finite CH 4 concentration difference ACme. Three estimates of the eddy diffusivity K were inferred using micrometeorological tech-SIMPSON ET AL.' TUNABLE DIODE LASER MEASUREMENT OF METHANE FLUXES 7285 OF METHANE FLUXES 7289

Environmental pests may serve as reservoirs and vectors of zoonotic pathogens to leafy greens; however, it is unknown whether insect pests feeding on plant tissues could redistribute these pathogens present on the surface of leaves to internal sites. This study sought to differentiate the degree of tissue internalization of Escherichia coli O157:H7 when applied at different populations on the surface of lettuce and spinach leaves, and to ascertain whether lettuce-infesting insects or physical injury could influence the fate of either surface or internalized populations of this enteric pathogen. No internalization of E. coli O157:H7 occurred when lettuce leaves were inoculated with 4.4 log CFU per leaf, but it did occur when inoculated with 6.4 log CFU per leaf. Internalization was statistically greater when spinach leaves were inoculated on the abaxial (underside) than when inoculated on the adaxial (topside) side, and when the enteric pathogen was spread after surface inoculation. Brief exposure (∼18 h) of lettuce leaves to insects (5 cabbage loopers, 10 thrips, or 10 aphids) prior to inoculation with E. coli O157:H7 resulted in significantly reduced internalized populations of the pathogen within these leaves after approximately 2 weeks, as compared with leaves not exposed to insects. Surface-contaminated leaves physically injured through file abrasions also had significantly reduced populations of both total and internalized E. coli O157:H7 as compared with nonabraded leaves 2 weeks after pathogen exposure.

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