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In recent decades, several standard colorimetric reactions for chemical analysis have been miniaturized to microwells on microplates, including methods useful for environmental measurements. Advantages of method miniaturization include a reduction in reagents required, improved safety, reduced waste stream, and increased sample throughput. However, the widespread use of microscale techniques employing microplates in classroom settings is likely limited by the high cost of microplate readers. Although spectrophotometers read peaks of specific wavelengths, absorbance spectra tend to be relatively broad and measurements at specific wavelengths are highly autocorrelated with those of nearby neighbors, which implies that broadband intensity data of red, green, and blue channels may indeed be adequate for digital colorimetric quantification. In this article, we demonstrate that digital image analysis of a scanned microplate image can substitute for a spectrophotometer for several common quantitative microscale procedures. This finding allows for cost effective and microscale quantification of several compounds to be demonstrated in the laboratory. Additionally, popular teaching and learning activities such as water quality monitoring can now be performed accurately and inexpensively using digital image analysis.
Trinexapac-ethyl (TE) is a widely used growth regulator in the turfgrass industry. Poor summer efficacy has been related to more rapid metabolism in the plant. The purpose of this study was to determine if a growing degree day (GDD) model could be used to identify the optimum TE reapplication interval for putting greens. This objective was accomplished through model development and validation. Model development was conducted on a creeping bentgrass {Agrostis stolonifera L.) golf putting green in Madison, Wl, during 2008. The treatments consisted of five TE reapplication intervals (100, 200, 400, 800 GDD, and 4 wk) and a control. Growing degree days were calculated in degrees G with a base temperature of 0°G. Trinexapac-ethyl was applied at the rate of 0.05 kg a.i. ha"^ Clippings were collected daily. The 100-and 200-GDD reapplication intervals provided consistent 20 and 12% yield suppression, respectively. Other reapplication intervals had alternating periods of yield reduction followed by yield enhancement. Model validation occurred on a different creeping bentgrass green in 2009 and 2010. The experiment was a 3 X 2 factorial GRD with three TE rates (0.00, 0.05, and 0.10 kg a.i. ha"^) and two reapplication frequencies (200 GDD and 4 wk). The 200-GDD interval consistently suppressed clipping yield. Application rate had no effect on the duration of suppression. Reapplying TE every 200 GDD provides more consistent growth regulation than a calendar-based application schedule.
Evaluation of turfgrass performance at low nitrogen fertility levels is important because many home lawns are fertilized below common recommendations. The objective of this study was to evaluate visible quality and weed susceptibility of common and alternative cool season grasses under multiple management regimes in Wisconsin. A split-split plot completely randomized block design was used to evaluate ‘Kingfisher' Kentucky bluegrass (Kentucky bluegrass), ‘Kenblue' Kentucky bluegrass, ‘Victory II' chewings fescue, ‘Grande II' tall fescue, and ‘Jiffe II' perennial ryegrass. Each species was mowed at 3.5, 6.0, or 8.5 cm, and fertilized with 0, 98, or 196 kg ha−1yr−1of nitrogen. Visible quality and weed cover were evaluated four times annually for 3 yr. Tall fescue had the greatest turf quality across all treatments. Kingfisher Kentucky bluegrass, an improved variety, responded most dramatically to nitrogen fertilization, with quality rating improved from 5.1 to 7.1 when annual nitrogen applications totaled 196 kg ha−1compared to the nonfertilized control. Kenblue Kentucky bluegrass, a common variety, had the greatest weed cover at all mowing heights and fertilizer rates. Assessment of common dandelion flowers by digital image analysis revealed that improved and common Kentucky bluegrass had greater common dandelion cover than fine or tall fescue when herbicides were withheld for 2.5 yr. Background soil fertility was found to have a significant impact on visible quality and weed cover. In an area with eroded, low-fertility soil, improved Kentucky bluegrass required 196 kg N ha−1yr−1to maintain high quality and limit weed invasion. These results suggest that tall fescue is best suited to low and high input conditions, while improved varieties of Kentucky bluegrass performed acceptably only under high inputs.
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