Reflectance‐based vegetation indices are commonly used to quantify turfgrass color, estimate chlorophyll content, and make inferences about plant health. These methods are often substituted for visual color ratings, as they are well correlated but more objective. This study examines the utility of reflectance‐based vegetation indices for evaluating turfgrass treated with iron or plant colorants. In a study in Madison, WI, creeping bentgrass (Agrostis stolonifera L.) was treated with ammonium sulfate (2.4 or 9.8 kg nitrogen [N] ha−1), Turf Screen (untreated or 4.0 L ha−1), or ferrous sulfate (untreated or 12.2 kg Fe ha−1). Visual color ratings, chlorophyll index (CI), normalized difference vegetation index, normalized difference red edge, red, and near‐infrared (NIR) reflectance were able to detect differences in N rate. When colorant or iron was applied, however, reflectance methods could no longer detect these differences in N rate. In a study in Ithaca, NY, the application of four colorants increased visual color ratings. The pigments Harmonizer and Foursome also increased CI, whereas Turf Screen and Green Lawnger did not. Three of the four pigments decreased the chlorophyll content in leaf tissue from 1 July to 22 August, despite having greater or equal CI values. Spectral analysis of six colorants revealed that these products reflect light in the red and NIR regions and likely interfere with reflectance‐based vegetation indices, which measure leaf reflectance in these same regions of the spectrum. Overall, these findings suggest that reflectance‐based vegetation indices should not be used to make inferences about plant health in studies where a colorant or iron is applied.

The performance of plant growth regulators (PGRs) in turfgrass is closely related to air temperature. Growing degree‐days (GDD) have been used to predict the performance of a foliar‐absorbed PGR, trinexapac‐ethyl (TE), on creeping bentgrass (Agrostis stolonifera L.). Similar models have not been attempted for paclobutrazol, a root‐absorbed PGR. This research aimed to develop GDD models (base temperature = 0°C) for paclobutrazol applied alone or in combination with TE. Models were developed on creeping bentgrass putting greens in Madison, WI (2009) and near Mead, NE, (2014 and 2015). Paclobutrazol was applied alone or with TE at various rates each year. Clippings were collected several times each week and treatments were reapplied when the PGR's effects expired. Sinewave regression models fitted relative clipping yield to GDD accumulation following the most recent PGR application. Relative clipping yield from all treatments was described by symmetric sinewave regression (adjusted R2: 0.409–0.862). The intensity of clipping yield suppression, expressed by the model amplitude, ranged from 0.293 to 0.621 g g−1, depending on the application rate or the addition of TE. The application rate had less effect on the duration of the growth response, represented by the model period. The estimated reapplication intervals ranged from 269 to 302 GDD. Tripling the application rate lengthened the estimated reapplication interval by <2 d. The addition of TE did not accelerate peak suppression and had a small, inconsistent impact on the model period. Golf course superintendents should use GDD models to schedule reapplications to sustain season‐long yield suppression.

Land application of biosolids holds the potential to reduce or eliminate the need for synthetic fertilizer applications. The objective of this study was to evaluate the agronomic impacts of using biosolids to produce Kentucky bluegrass (Poa pratensis L.) sod on a silt loam soil in Wisconsin. Anaerobically digested biosolids cake and biosolids cake mixed with sand and sawdust in a 2:1:1 ratio by volume (MetroMixTM) were produced by and obtained from the Madison Metropolitan Sewerage District. Each material was applied at three rates based on their estimated supply of plant‐available nitrogen (PAN). The control treatment mimicked conventional sod maintenance techniques using synthetic fertilizer applied at 309 kg N ha−1 over the 20‐mo production cycle. All biosolids treatments improved or exhibited similar establishment cover compared with the conventional practice. However, generally the lowest rate of cake and the two lowest rates of the MetroMix underperformed the conventional production in terms of visual quality throughout harvest and into transplanting. Cake had superior visual quality compared with MetroMix when applied at equivalent PAN rates. Optimization modeling determined that a biosolids cake application rate of 425 kg PAN ha−1 would likely meet agronomic standards (quality, color, sod strength, etc.) of the conventional practice. Repeated applications decreased the optimized biosolids rate to from 425 to 325 and 285 kg PAN ha−1, depending on number of previous applications. These results suggest that biosolids‐based sod production has the potential to replace or supplement traditional fertilization practices to meet current agronomic goals for sod production in Wisconsin.

Fungicide applications to turfgrass that coincide with oviposition and egg hatch of white grubs may have sublethal effects. This work is applicable both to high-maintenance turfgrass such as golf courses, where applications of pesticides are more frequent, and to home lawn services, where mixtures of multiple pesticides are commonly used.

There is a widely‐held belief in the turfgrass industry that irrigating with water high in bicarbonate will result in carbonate accumulation in the soil, despite a lack of evidence for this claim. While water quality problems are traditionally associated with arid regions, water quality recommendations are being applied to more humid regions where there is a lack of research to correlate water chemistry with soil properties. The objective of this study was to investigate the relationships among soil properties, climate, and irrigation water quality for golf courses across the United States. This study examines the vertical distribution of soil inorganic carbon (SIC) in 28 sand putting green soils across a range of geographic locations and climates. Soils below a pH of 7.8 had very little inorganic carbon, and soils above this pH had variable levels of inorganic carbon. There was no relationship between SIC and the estimated bicarbonate load from irrigation water, mean annual precipitation (MAP), or annual potential evapotranspiration (ETp). Our findings from this study do not provide evidence that bicarbonate from irrigation will cause formation of layers or zones of accumulation in putting green soils, contrary to this widely‐held belief in the turfgrass industry.