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- Author or Editor: Paul G. Johnson x
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Visual ratings are the standard for evaluating turfgrass quality. However, to provide more objective evaluations and to address statistical concerns, other methods have been developed to measure turfgrass quality, including digital image analysis and measurements of chlorophyll content. These have been largely applied to traditionally used turfgrass species, but here we used these methods to evaluate turfgrass quality of nontraditional species and mixtures that are native or adapted to the intermountain west region of North America. Two fertilizer treatments (1.0 or 2.0 lb/1000 ft2 nitrogen) were applied to 21 different species and species mixtures in North Logan, UT. These plots were irrigated to replace 60% of the local evapotranspiration rate and were mowed at 4 inches. Turfgrass quality ratings were most effective in measuring quality among the diverse species used in this study. Because of the wider variation in acceptable visual characteristics and lower quality expectations for low-maintenance native turf, the objective evaluation methods proved less useful. Generally, chlorophyll meter data, digital image analysis of cover, and digital image analysis of color data were not well correlated with human visual quality ratings in this study. Measurements were well correlated in some species, but not in others. These methods can supplement, but cannot replace, human visual turfgrass quality ratings for comparison of dissimilar grasses.
Recent advances in irrigation technologies have led many states to incentivize homeowners to purchase United States Environmental Protection Agency WaterSense-labeled, smart irrigation controllers. However, previous research of smart controllers has shown that their use may still result in excess water application when compared with controllers manually programmed to replace actual water loss. This study compared kentucky bluegrass (Poa pratensis) irrigation applications using three smart irrigation controllers, a conventional irrigation controller programmed according to Cooperative Extension recommendations, and the average irrigation rate of area homeowners in Utah during 2018 and 2019. Of all the controllers tested, the manually programmed controller applied water at amounts closest to the actual evapotranspiration rates; however, smart controllers applied from 30% to 63% less water than area homeowners, depending on the controller and year of the study. Kentucky bluegrass health and quality indicators—percent green cover and normalized difference vegetation indices—varied between years of the study and were lower than acceptable levels on several occasions in 2019 for three of the four controllers tested. Compared with the results of similar studies, these findings suggest that the effects of smart irrigation controllers on turfgrass health and quality may vary by location and over time.