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Mowing remains one of the most energy‐intensive cultural practices in maintaining a turf sward. Turfgrass systems can become a larger net C sink if mower emissions are reduced. Establishing slow‐growing turfgrasses has been proposed to reduce mowing requirements. Traditional recommendations for home lawns are to mow by the “one‐third rule” and return grass clippings. However, their impact on annual mowing requirements remains largely unknown. This study aimed to determine (i) the number of required mowing events when mowing weekly versus using the one‐third rule; (ii) the influence of returning grass clippings on mowing requirements, dry matter yield (DMY), and leaf tissue N (LTN); and (iii) how turfgrasses with differing growth rates influence mowing requirements, DMY, and LTN. The one‐third rule decreased mowing requirements by 31% (approximately eight mowing events yr−1) and returning grass clippings added approximately two additional mowing events yr−1. Tall fescue [Schedonorus arundinaceus (Schreb.) Durmort., nom. cons.; Festuca arundinacea Schreb.] required more annual mowing events than Kentucky bluegrass (Poa pratensis L.)(nine and three more in 2012 and 2013, respectively). Tall fescue had a greater 2‐yr cumulative DMY than Kentucky bluegrass (875 vs. 522 g m−2). Growth rate (i.e., cultivar) also affected annual mowing requirements and yield: the faster the growth rate, the more annual mowing events. Leaf tissue N concentrations were higher when clippings were returned and with slower‐growing cultivars. Mowing by the one‐third rule and selecting slower‐growing cultivars of turfgrass species adapted to a particular location can reduce annual mowing requirements and subsequent mower emissions.

Core Ideas Less than 3 yr post‐establishment, tall fescue accumulated more soil C (i.e., labile soil C, total soil C, and soil organic matter) than Kentucky bluegrass. Returning grass clippings for 2 yr increased both soil C (i.e., labile soil C and total soil C) and N (i.e., total soil N) compared to collecting clippings over the same period. Labile soil C increased linearly over the 5 yr of the experiment. Little information is available about how grass species and management practices, such as grass clippings management, influence soil C and N accumulation, especially labile soil C. Thus, the objective of this field experiment was to determine the labile soil C, total soil C, soil organic matter (SOM), and total soil N accumulation of Kentucky bluegrass (Poa pratensis L.) and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort. syn. Festuca arundinacea Schreb. syn. Lolium arundinaceum (Schreb.) Darbysh.] cultivars with differing growth rates under different grass clippings management practices. Differences in labile and total soil C occurred between turfgrass species after less than 3 yr of growth post planting: labile soil C was 9.9% higher (851 vs. 774 mg C kg−1 soil), total soil C was 4.2% higher (24.8 vs. 23.8 g C kg−1 soil), and SOM was 8.0% higher (41.7 vs. 38.6 g SOM kg−1 soil) for tall fescue than Kentucky bluegrass. After 2 yr of clippings management treatments, plots where grass clippings were returned had 3.3% more labile soil C (826 vs. 800 mg C kg−1 soil), 3.3% more total soil C (24.7 vs. 23.9 g C kg−1 soil), and 4.6% more total soil N (2.28 vs. 2.18 g N kg−1 soil) than those where clippings were collected. However, grass clippings management did not affect SOM. The results of this study highlight the importance of turfgrass selection and grass clippings management on soil C and N accumulation.

Continued reliance on chemical methods for controlling annual bluegrass has resulted in many populations evolving resistance to PRE and POST herbicides, particularly in warm-season turfgrass species such as zoysiagrass. Soil seedbank management is critically important when managing herbicide-resistant weeds. Fraise mowing (also spelled fraze, frase, and fraize) is a new turfgrass cultivation practice designed to remove aboveground biomass while allowing turf to regrow vegetatively. We hypothesized that this process would remove annual bluegrass seed and therefore be a mechanical means of controlling annual bluegrass in turfgrass. Zoysiagrass field plots were fraise-mowed in June 2015 only, June 2016 only, June 2015 and June 2016, or left untreated. The fraise mower was configured to remove the uppermost 25 mm of plot surface (i.e., 15-mm verdure and 10-mm soil). Annual bluegrass infestation was quantified in April following fraise mowing via grid count. Soil cores (10.8 cm diameter) were extracted from each plot after grid count data were collected to assess effects of fraise mowing on the soil seedbank. Moreover, replicated subsamples (7.6 L) of debris generated during fraise mowing were collected to better understand weed seed content removed during the fraise mowing process. Fraise mowing in June offered a slight reduction (24%) in annual bluegrass cover the following April. Whereas 28% of the seed in fraise-mowing debris consisted of annual bluegrass, there was no difference in the quantity of annual bluegrass seed remaining in the soil seedbank among fraise-mowed and non–fraise-mowed plots. Although fraise mowing may help to temporarily reduce existing annual bluegrass infestations via mechanical removal, the frequency and depth we studied did not effectively reduce the seedbank. Fraise mowing is a useful tool for providing mechanical suppression of annual bluegrass but it is not a replacement for properly timed herbicide applications.

Mesotrione, a 4-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide, is labeled for PRE and POST crabgrass control. It has enhanced efficacy on smooth and large crabgrass when applied in conjunction with soil-applied nitrogen (N). The objectives of this study, using crabgrass as the weed species, were to (1) determine the influence of N rate and tissue N concentration on mesotrione activity, (2) determine the influence of N source on mesotrione activity, and (3) determine the influence of N application timing on mesotrione activity. Large crabgrass plants that received 12 kg N ha−1or more before mesotrione application had more bleached and necrotic leaves compared with plants that received 0 kg N ha−17 d after treatment (DAT) in the greenhouse. Although N application rates as high as 98 kg N ha−1were tested, 90% leaf bleaching and necrosis were observed with rates of 8.9 or 10.1 kg N ha−1in Tennessee and Indiana, respectively. Nitrogen concentration in large crabgrass leaf and stem tissue on the day of the mesotrione application was closely related to the bleaching and necrosis symptoms observed 7 DAT. Although N rate influenced mesotrione activity, N source did not. Nitrogen application timing was also important, with N applications 3, 1, and 0 d before a mesotrione application having the highest percentage of bleached and necrotic leaves in greenhouse experiments. Both greenhouse and field trials support the finding that N applications in proximity to the mesotrione application enhance herbicide activity. Thus, practitioners can pair N and POST mesotrione applications together or in proximity to enhance crabgrass control.

Turfgrass systems can be an important source or sink for greenhouse gases (GHG), including carbon dioxide (CO 2 ), nitrous oxide (N 2 O), and methane (CH 4 ). Further research is required in turfgrass systems; therefore, our objectives were to evaluate the effects of turfgrass species, growth rate, clipping management, and environmental conditions on GHG emissions. Greenhouse gas fluxes were measured in two separate field experiments in West Lafayette, IN. Experiment 1 investigated GHG flux in three cool-season (C 3 ) and two warm-season (C 4 ) turfgrass species during two growing seasons. Experiment 2 investigated fluxes in two C 3 cultivars with varying growth rates and under different clipping management regimes. The C 3 turfgrasses had the highest mean CO 2 flux rates ranging from 0.373 to 0.431 g CO 2 -C m −2 h −1 compared with 0.273 to 0.361 g CO 2 -C m −2 h −1 for C 4 turfgrasses. Mean hourly N 2 O flux rates ranged from 43.3 to 50.9 μg N 2 O-N m −2 h −1 for C 3 compared with 11.1 to 14.4 μg N 2 O-N m −2 h −1 for C 4 turfgrasses. Methane flux was more variable across time, but overall C 4 turfgrasses were more likely to be a CH 4 source, whereas C 3 turfgrasses were often a CH 4 sink. Growth rate and grass clipping management treatments had negligible impact on measured GHG flux. The differences in management practices specific to C 3 and C 4 turfgrasses had the largest impact on GHG flux.Results indicate the impact and importance of turfgrass species selection on GHG flux and also provide more information on our overall understanding on carbon and nitrogen cycling in urban soils.

Digital image analysis provides researchers a method to accurately and efficiently analyze turfgrass parameters including cover, color, disease severity, and more. Opportunities for processing images has increased due to the free and open-source nature of many new programs. We developed a macro (set of macroinstructions) within the open-source software ImageJ that is able to count the number and quantify the percent coverage of dandelion (Taraxacum officinale F.H. Wigg.) blooms in field plot images, which allows for collection of objective data on broadleaf weeds. A particle analysis function in ImageJ was used to distinguish dandelion blooms from other yellow objects (e.g. chlorotic turfgrass leaves) based on their size and circularity. We also explored the use of binary watershed segmentation to separate groupings of dandelion blooms into individual blooms that could be counted. To verify the accuracy of the macro, we analyzed 164 images for the number of dandelion blooms with the macro and regressed data against visual counts of dandelion bloom. The resulting linear regression analysis (visual count vs. macro) had a slope of 1.034 and an R 2 value of 0.9795. This macro provides researchers with a rapid and accurate method of determining the number and percent coverage of dandelion blooms in field plots using image analysis.