Bans on the use of synthetic herbicides require innovative management approaches to maintain the attractiveness and usability of turfgrass swards. Such measures should include the use of locally adapted cultivars that germinate and establish quickly, resulting in the densest possible stands. Additionally, a number of turfgrasses have been reported to produce allelopathic substances that inhibit common turfgrass weeds. Mowing heights should be set to achieve maximum weed suppression while still providing acceptable quality for desired use. Sustainable turfgrass management programs have led to a reduction in fertilizer inputs; however, without the availability of herbicides, fertilization regimes need to be re‐examined. The literature suggests that broadleaf weeds are reduced but never fully controlled when more N is applied; therefore, finding a balance between what is needed and what is environmentally safe and sustainable is critical. Organic herbicides include plant pathogens from the fungus Phoma and strains of the bacterium Pseudomonas fluorescens. Both can be used to control several weeds common to turfgrasses. Acetic acid has also been shown to have herbicidal activity; however, it has limited residual activity, and its efficacy remains questionable on mature weeds. Thermal weed control can be used to sterilize a seedbank or spot treat existing weeds. Future turfgrass breeding programs could focus on understanding and enhancing the allelopathic potential of turfgrasses to outcompete weeds more effectively. Furthermore, more research should be directed at assessing the competitiveness of certain turfgrasses against weeds within the limitations of producing turfgrass areas of acceptable aesthetics and playing quality.
The current practice used to evaluate broadleaf weed cover in turfgrass is visual assessment, which is time consuming and often leads to inconsistencies among evaluators. In this study, we investigated the effectiveness of constructing Random Forest models (RF), either pixel-, object-based (OBIA) or a combination of both to detect and quantify broadleaf weed cover. High resolution multispectral images were captured of 136 turfgrass plots, seeded with five species of Festuca L. and overseeded with either clover (Trifolium repens L.), daisy (Bellis perennis L.), yarrow (Achillea millefolium L.), or a mixture of all three weeds. Ground measurements of vegetation cover and bare soil were taken with a point quadrat and digital image analysis. Weeds were detected with 99% accuracy by OBIA, followed by the combined approach (98%) and Pixelbased approach (93%). Accuracy at distinguishing among weed species was somewhat lower (89%, 81% and 90%, respectively), with yarrow contributing most to the decrease in accuracy. The predictions based on ground measurements were further compared to field measurements. For both soil and weed classification, models that used shape features (OBIA and combined) resulted in better agreement with field measurements compared to Pixelbased classifications. Our study suggests that broadleaf weed cover comprised of species such as clover and daisy can be accurately quantified with high resolution multispectral images; however, quantifying yarrow cover remains challenging.
Regulatory restrictions on herbicide use for managing turfgrass weeds has prompted the search for alternative control strategies. Fescue (Festuca) species were identified for their potential to interfere with growth of annual and perennial weeds. In a study conducted in 2018 and 2019, six fescue cultivars were tested from five different species for interference with the growth of three common turfgrass weeds: white clover (Trifolium repens L., WC), daisy (Bellis perennis L.) and yarrow (Achillea millefolium L.). Fine (Festuca L. spp.) and tall fescues (Schedonorus arundinaceus (Schreb.) Dumort.) were sown and grown in a field trial for 14 days before overseeding with different weeds. vigor and visual quality of grasses, weed cover, and vegetation cover was recorded regularly for 84 days. Differences in mean temperatures and precipitation between the two years of the study resulted in differences in growth of grasses and weeds, as well as in the extent of weed interference of fescue cultivars. Cultivars Musica (F. rubra L. ssp. commutata Gaudin) and Barpearl (F. rubra L. ssp. littoralis) were least affected by weed growth during both years, but there was overlap with other cultivars for the measured parameters. Melyane (tall fescue) was deemed unsuitable for natural weed suppression because growth and vigor declined after first mowing, ultimately leading to unacceptable visual quality. Turfgrass visual scores were moderately negatively correlated to weed cover in both years. Future research should focus on F. rubra L. ssp. rubra Gaudin and F. rubra L. ssp. littoralis subspecies and identify the mechanisms used to interfere with weed growth.
In this paper we present an assistive system for hearing-impaired people that consists of a wearable microphone array and an Augmented Reality (AR) system. This system helps the user in communication situations, where many speakers or sources of background noise are present. In order to restore the "cocktail party" effect multiple microphones are used to estimate the position of individual sound sources. In order to allow the user to interact in complex situations with many speakers, an algorithm for estimating the user's attention is developed. This algorithm determines the sound sources, which are in the user's focus of attention. It allows the system to discard irrelevant information and enables the user to focus on certain aspects of the surroundings. Based on the user's hearing impairment, the perception of the speaker in the focus of attention can be enhanced, e.g. by amplification or using a speech-to-text conversion. A prototype has been built for evaluating this approach. Currently the prototype is able to locate sound beacons in three-dimensional space, to perform a simple focus estimation, and to present floating captions in the Augmented Reality. The prototype uses an intentionally simple user interface, in order to minimize distractions.
The sportsturf industry in Europe is moving toward non-chemical broadleaf weed management.This thesis explored building a framework for alternative weed management strategies in turfgrass areas. Most importantly, I focused on the strategy of using suitable turfgrass species to maintain vigorous, dense turfgrass that is competitive against weeds. In light of climate change and stricter regulations regarding water, fertilizer and pesticide use, practitioners recently opted to use low input species such as Festuca spp. We therefore investigated the growth interfering capacity of 27 cultivars from five Festuca species (Chewings fescue [F. rubra L. ssp. fallax (Thuill.) Nyman], slender creeping red fescue [F. rubra L. ssp. littoralis (G.Mey.) Auquier] strong creeping red fescue [F. rubra L. ssp. rubra Gaudin], hard fescue [F.brevipila Tracey] and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.]) against three common broadleaf turfgrass weeds, namely clover (Trifolium repens L.), daisy (Bellis perennis L.) and yarrow (Achillea millefolium L.). In a climate chamber, 60 Festuca seeds were placed on water agar in a series of plastic containers for 30 days. Thirteen days after sowing, twenty weed seeds were introduced to each container, and germination and root length of those weeds was recorded. Interference by presence of Festuca species did not affect weed seed germination, but a pronounced negative effect on weed root growth was observed, with reductions of up to 85%. Clover was most severely affected in the presence of tall fescue, whereas all fescue species caused a similar reduction in root length for yarrow. Within most Festuca species we observed cultivar differences in growth interfering capacity. Weed species used in this experiment differed in their susceptibility to interference by fescue, with yarrow being more sensitive to growth interference by Festuca cultivars than clover. Daisy was most sensitive, and due to high mortality rates the species was removed from the experimental analysis. While we conducted the growth chamber screening, we also sowed a field trial with six cultivars representing each species used in the growth chamber experiment and four weed treatments including clover, daisy, yarrow and a mixture of these species in a randomized block design replicated by year. Weather conditions varied between years and caused different results, however cultivar Musica (Chewings fescue) and Barpearl (slender creeping red fescue) were least affected by weed growth over both years and resulted in acceptable visual sward quality.Manual counting of weeds with a 100-point quadrat in the above-described experiment was time consuming and limited the number of recordings. We therefore collected aerial multispectral images and applied random forest model (RF) machine learning algorithms to quantify vegetation cover using image analysis. Object-based classification using spectral features from a previous segmented orthoimage resulted in highest classification accuracy to detect weeds with 99% acc...
Herbicide restrictions require alternative strategies for turfgrass weed control. This growth chamber study investigated the interference of 27 Festuca cultivars selected from five Festuca species using white clover (Trifolium repens L.), lawn daisy (Bellis perennis L.), and yarrow (Achillea millefolium L.) as indicator species. At 13 days after sowing (DAS), 20 weed seeds were placed in between 60 grass seeds. Lawn daisy was highly sensitive to the presence of all grasses, and results are not presented. Festuca species or individual cultivars did not affect the germination percentage and mean germination period of white clover and yarrow. The presence of tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.]) species reduced white clover root length by 71.6% and slender creeping red fescue [Festuca rubra L. ssp. littoralis (G.Mey.) Auquier] by 44.5% at 30 DAS. Within cultivars, reductions of white clover roots ranged from 81.7% (Regenerate) to 24.8% (Cathrine). Root length for yarrow was reduced by an average of 75% with no difference among Festuca species. Cultivar effects ranged from 91.8% for Barcesar to 62.9% for Samanta. For both white clover and yarrow, negative correlations were determined between Festuca biomass and the root length of both weeds: −0.241*** (white clover) and yarrow −0.168* (yarrow). Such a relationship suggests that part of the inhibiting effect can be directly attributed to Festuca biomass. We conclude that differences in interference potential between cultivars within species are as important as differences between species. White clover appeared to be the most discriminative species for growth interference studies with Festuca.
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