Monitoring turfgrass species by ground-based and satellite remote sensing

Like all modern agriculture sectors, turfgrass production and management is headed towards cost reduction, resource optimization and reduction of the environmental impact. In recent years, within the European Union several legislative, monitoring and coordinating actions have been undertaken to encourage sustainable use of resources, reduction in the use of chemicals and improvement of the urban environment. In this respect, two concepts that are strictly related to most of the aspects above are: “precision agriculture” and “precision conservation” and more specifically “precision turfgrass management.” Optical sensing has become a crucial part of precision turfgrass management and spectral reflectance in particular has been an active area of research for many years. However, while turfgrass status evaluation by proximity-sensed spectral reflectance appears to be an established and reliable practice, much more could be achieved in terms of monitoring of large turfgrass areas through remote sensing, and in particular through satellite imagery. This thesis reports the results of four trials attempting: a) to evaluate the spectral signatures of several turfgrass species\cultivars, for future use in satellite monitoring. This experimental study focused on 20 turfgrass species\cultivars, including perennial ryegrasses, tall fescues, kentucky bluegrasses, bermudagrasses (ecotypes, seeded and vegetatively propagated cultivars) and zoysiagrasses. Various agronomical and biological parameters were studied (quality, color, dry matter, chlorophyll, carotenoids, nitrogen content) and turfgrass spectral reflectance for all entries was gathered. Results showed that, within the same species, selected vegetation indices are often able to discriminate between different cultivars that have been established and maintained with identical agronomical practices. Evaluation of the spectral reflectance of plants using field spectroradiometry provides the possibility to identify different species\ cultivars, especially through the use of hyperspectral proximity and remote sensing; b) to calculate on these 20 species and cultivars the most interesting vegetation indices by simulating the available wavelengths deriving from World View 2 satellite imagery. Results showed that within the same species selected vegetation indices are often able to discriminate between different varieties that have been established and maintained with identical agronomical practices; c) to evaluate the proximity sensed spectral reflectance on Festuca arundinacea turf with 9 water replenishment levels (Linear Gradient Irrigation System) and 2 nitrogen conditions. ET0 was estimated using the Hargreaves and Samani method. The following parameters were determined: turf quality, drought tolerance, pest problems, temperature of the surface, clippings weight and relative nitrogen content, turf growth and soil moisture. Spectral reflectance data were acquired using a LICOR 1800 spectroradiometer. Pearson correlation coefficients were studied among all parameters and vegetation indices. Nitrogen fertilization influenced significantly turf quality, clippings weight, nitrogen content and turf growth. Water replenishment influenced significantly all parameters except nitrogen content. Among all parameters the highest correlation coefficient was registered relating drought tolerance with turf quality (r = 0.88) and with surface temperature (r = - 0.88). Among vegetation indices results showed that Water Index (WI) and Normalized Difference Water Index (NDWI), are better able to discriminate between different levels of water replenishment. Comparing WI with NDWI, the correlation coefficients were higher for Water Index in all the parameters, in particular the highest WI value was registered for drought tolerance (r = 0.91). This preliminary research demonstrates that spectral remote sensing can be a useful diagnostic tool to detect water stress in turfgrasses; d) to compare N status in different turfgrasses, from remote multi-spectral data acquired by GeoEye-1 satellite and by two ground-based instruments. The study focused on creating a nitrogen concentration gradient on 3 warm-season turfgrasses (Cynodon dactylon x transvaalensis ‘Patriot’, Paspalum vaginatum ‘Salam’, Zoysia matrella ‘Zeon’) and 2 cool-season (Festuca arundinacea ‘Grande’, Lolium perenne ‘Regal 5’). The linear gradient ranged from 0 to 342 kg ha-1 of N for the warm-season and from 0 to 190 kg ha-1 of N for the cool-season turfgrasses. Proximity and remote reflectance measurements were acquired and used to determine Normalized Difference Vegetation Index (NDVI). Results showed that the N status is highly correlated with the spectral reflectance. Our results prove that NDVI measured with the ground-based instruments are highly correlated with data from satellite. The correlation coefficients between the satellite and the other sensors ranged from 0.90 to 0.99 for the warm-season and from 0.83 to 0.97 for the cool-season species. 'Patriot' had a clippings N concentration ranging from 1,20 % to 4.1 %, thus resulting the most reactive species to N fertilization. GeoEye-1 satellite can adequately assess the N status of different turfgrass species, and its spatial variability within a field depending on the N rates applied on the surfaces. In future information obtained from satellite could allow target management depending on the real need of the turf

Carbohydrate Metabolism During Wintering Period in Four Zoysiagrass Genotypes

A key barrier to widespread use of warm-season grasses in the transition zone between the temperate and subtropical climates is represented by the winter dormancy, a temporary suspension of visible growth of any plant structure including the meristem. In this environment, species with different photosynthetic carbon cycle coexist, leading to asynchrony in growth among warm- and cool-season grasses. The objectives of the present study were (i) to assess the carbohydrate content in four representative zoysiagrasses Zoysia japonica 'El Toro', 'Meyer', Z. pacifica, and Z. matrella 'Zeon' during three successive phases of vegetation phenology, senescence, dormancy, and green-up, and (ii) to characterize the metabolic responses to phenological variations under natural acclimation. Japanese lawn grass genotypes 'El Toro' and 'Meyer' showed longer dormancy periods than fine-leaved Z. pacifica and 'Zeon'. In Japanese lawn grass genotypes, the progressive decline of photosynthetic pigments was similar to that observed in the color retention. Over the experimental period, a significantly greater amount of starch reserves was observed in sprigs (horizontal stems) in the Japanese lawn grasses than in the fine-leaved zoysiagrasses. In general, total soluble sugars (TSS) in leaves and sprigs did not show evidence of sugar starvation during the senescence phase. TSS increased significantly during cold acclimation, resulting in a higher metabolic activity at the onset of green-up to support spring regreening in all zoysiagrasses except 'Meyer' leaves

Spectral Reflectance of Tall Fescue (Festuca Arundinacea Schreb.) Under Different Irrigation and Nitrogen Conditions

The issue of water and climate change is present in many countries. Drought stress is one of the main abiotic stresses influencing turfgrass growth and quality. Tall fescue is the most suitable cool-season turfgrass for the Mediterranean region. This species has a better heat tolerance than perennial ryegrass and Kentucky bluegrass. The analysis of radiation reflected by turfgrass can supply precious information on drought stress and nutritional status. In this study a Linear Gradient Irrigation System (LGIS) was adopted on a Festuca arundinacea turf with 9 water replenishment levels and 2 nitrogen conditions, to evaluate the proximity sensed spectral reflectance. ET0 was estimated using the Hargreaves and Samani method. The following parameters were determined: turf quality, drought tolerance, pest problems, temperature of the surface, clippings weight and relative nitrogen content, turf growth and soil moisture. Spectral reflectance data were acquired using a LICOR 1800 spectroradiometer. Pearson correlation coefficients were studied among all parameters and vegetation indices. Nitrogen fertilization influenced significantly turf quality, clippings weight, nitrogen content and turf growth. Water replenishment influenced significantly all parameters except nitrogen content. Among all parameters the highest correlation coefficient was registered relating drought tolerance with turf quality (r = 0.88) and with surface temperature (r = - 0.88). Among vegetation indices results showed that Water Index (WI) and Normalized Difference Water Index (NDWI), are the most suitable to discriminate between different levels of water replenishment. Comparing WI with NDWI, the correlation coefficients were higher for Water Index in all the parameters, in particular the highest WI value was registered for drought tolerance (r = 0.91). This preliminary research demonstrates that spectral remote sensing can be a useful diagnostic tool to detect water stress in turfgrasses

Use of Flaming to Control Weeds in ‘Patriot’ Hybrid Bermudagrass

Flaming could be an alternative to the use of chemical herbicides for controlling weeds in turfgrass. In fact, the European Union has stipulated that chemical herbicides should be minimized or prohibited in public parks and gardens, sports and recreational areas, school gardens, and children’s playgrounds. The aim of this research was to test different doses of liquefied petroleum gas (LPG) to find the optimal flaming dose that keeps a ‘Patriot’ hybrid bermudagrass (Cynodon dactylon · Cynodon transvaalensis) turf free of weeds during spring green-up, but also avoids damaging the grass. Five LPG doses (0, 29, 48, 71, and 100 kgha–1) were applied in a broadcast manner over the turf experimental units using a selfpropelled flaming machine. This equipment is commercially available and usable by turfgrass managers. Treatments were applied three times during the spring to allow the maximum removal of weeds from the turfgrass. Data on weed coverage, density, biomass, and turfgrass green-up were collected and analyzed. Results showed that 3 weeks after the last flaming, the greatest LPG doses used (i.e., 71 and 100 kgha–1) ensured the least amount of weeds (range, 5–16 weeds/m2) of low weight (range, 7– 60 gm–2) and a low weed cover percentage (range, 1% to 5%), whereas the green turfgrass coverage was high (range, 82% to 94%). At the end of the experiment, the main weed species were horseweed (Conyza canadensis), field bindweed (Convolvulus arvensis), narrow-leaved aster (Aster squamatus), and black medic (Medicago lupulina). Flame weed control is a promising technique to conduct weed control in turfgrass. Further studies could be conducted to investigate the use of flaming in other species of warm-season turfgrasses

Autonomous rotary mower versus ordinary reel Mower-effects of cutting height and nitrogen rate on manila grass turf quality

High-quality sports turfs often require low mowing and frequent maintenance. Sports turfs often consist of hard-to-mow warm season turfgrasses, such as zoysiagrass (Zoysia sp.) or bermudagrass (Cynodon sp.). Although autonomous mowers have several advantages over manually operated mowers, they are not designed to mow lower than 2.0 cm and are consequently not used on high-quality sports turfs. All autonomous mowers are only equipped with rotary mowing devices and do not perform clipping removal. An ordinary autonomous mower was modified to obtain a prototype autonomous mower cutting at a low height. The prototype autonomous mower was tested on a manila grass (Zoysia matrella) turf and compared its performance in terms of turf quality and energy consumption with an ordinary autonomous mower and with a gasoline reel mower. A three-way factor experimental design with three replications was adopted. Factor A consisted of four nitrogen rates (0, 50, 100, and 150 kghaL1), factor B consisted of two mowing systems (autonomous mower vs. walk-behind gasoline reel mower with no clipping removal), and factor C consisted of two mowing heights (1.2 and 3.6 cm). Prototype autonomous mower performed mowing at 1.2-cm mowing height whereas ordinary autonomous mower mowed at 3.6-cm mowing height. The interaction between the mowing system and mowing height showed that the turf quality was higher when the turf was mowed by the autonomous mower and at 1.2 cm than at 3.6 cm. Autonomous mowing not only reduced the mowing quality, but also reduced the leaf width. Lower mowing height induced thinner leaves. Nitrogen fertilization not only increased the overall turf quality, reduced weed cover percentage, but also reduced mowing quality. Autonomous mowers also had a lower energy consumption if compared with the reel mower (1.86 vs. 5.37 kWh/ week at 1.2-cm mowing height and 1.79 vs. 2.32 kWh/week at 3.6-cm mowing height, respectively). These results show that autonomous mowers can perform low mowing even on tough-to-mow turfgrass species. They could also be used on highquality sports turfs, thus saving time as well as reducing noise and pollution

Steaming and flaming for converting cool-season turfgrasses to hybrid bermudagrass in untilled soil

Turfgrass species can be classified into two main groups: cool-season and warm-season species. Warm-season species are more suited to a Mediterranean climate. Transplanting is a possible method to convert a cool-season to a warmseason turfgrass in untilled soil. It generally requires the chemical desiccation of the cool-season turfgrass. However, alternative physical methods, like flaming and steaming, are also available. This paper compares flaming, steaming, and herbicide application to desiccate cool-season turfgrass, for conversion to hybrid bermudagrass (Cynodon dactylon x C. transvaalensis) in untilled soil, using transplanting. Two prototype machines were used, a self-propelled steaming machine and a tractor-mounted liquefied petroleum gas flaming machine. Treatments compared in this work were two flaming treatments and two steaming treatments performed at four different doses together with two chemical treatments with glufosinateammonium herbicide applications. The cool-season turfgrass species were tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne). The desiccation effect of the various treatments on cool-season turf was assessed by photographic survey 15 days after treatment. The percentage cover of hybrid bermudagrass was visually assessed at 43 weeks after planting. Steaming and flaming effects on both parameters were described by logistic curves. The highest doses of steaming and flaming almost completely desiccated cool-season turf, and similar hybrid bermudagrass cover was established by both the methods as the chemical application (50% to 60%). Thus both flaming and steaming may be considered as valid alternatives to herbicides aimed at turf conversion

St. Augustinegrass accessions planted in northern, central and southern Italy: Growth and morphological traits during establishment

The use of warm season turfgrasses is a consolidated trend in the climatic transition zone of Mediterranean countries, in particular St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze) begins to be widespread in warm coastal areas. However, little is known about the performance of the different cultivars of this species in southern Europe. In 2016-2017 a trial was carried out in three locations in Italy, Padova, Pisa, and Palermo, located in the north, center and south of the country respectively. Four cultivars (Floratine, Captiva, Sapphire, Palmetto) and five ecotypes (CeRTES 201, CeRTES 202, CeRTES 203, CeRTES 204, CeRTES 205) were compared in terms of their growth characteristics and morphological traits during establishment. The results highlighted that stolon growth was significantly affected by the location, as well as green colour retention. Stolon growth rate, internode length and internode volume and turf quality were, however, significantly determined by the accession effect. The quality of the ecotypes was also in some cases comparable to that of the cultivars. In Padova, winterkill occurred in most of the accessions while in Pisa and Palermo, all the entries survived. In conclusion, St. Augustinegrass is suitable for turf use in the central and southern coastal area of Italy

Autonomous Mower Saves Energy and Improves Quality of Tall Fescue Lawn

Battery-powered autonomous mowers are designed to reduce the need of labor for lawn mowing compared with traditional endothermic engine mowers and at the same time to abate local emissions and noise. The aim of this research was to compare autonomous mower with traditional rotary mower on a tall fescue (Festuca arundinacea) lawn under different nitrogen (N) rates. A two-way factor experimental design with three replications was adopted. In the study, fourNrates (0, 50, 100, and 150 kghaL1) and two mowing systems (autonomous mower vs. gasolinepowered walk-behind rotary mower equipped for mulching) were used. As expected, N fertilization increased turf quality. At the end of the trial, the autonomous mower increased turf density (3.2 shoots/cm2) compared with the rotary mower (2.1 shoots/cm2) and decreased average leaf width (2.1 mm) compared with the rotary mower (2.7 mm). Increased density and decreased leaf width with autonomous mowing yielded higher quality turf (7.3) compared with the rotary mower (6.4) and a lower weed incidence (6% and 9% cover for autonomous mower and rotary mower, respectively). Disease incidence and mowing quality were unaffected by the mowing system. The autonomous mower working time was set to 10 hours per day (7.8 hours for mowing and 2.2 hours for recharging) for a surface of 1296 m2. The traditional rotary mower working time for the same surface was 1.02 hours per week. The estimated primary energy consumption for autonomous mower was about 4.80 kWh/week compared with 12.60 kWh/week for gasoline-powered rotary mowing. Based on turf quality aspects and energy consumption, the use of autonomous mowers could be a promising alternative to traditional mowers

Unmanned aerial vehicle to estimate nitrogen status of turfgrasses

Spectral reflectance data originating from Unmanned Aerial Vehicle (UAV) imagery is a valuable tool to monitor plant nutrition, reduce nitrogen (N) application to real needs, thus producing both economic and environmental benefits. The objectives of the trial were i) to compare the spectral reflectance of 3 turfgrasses acquired via UAV and by a ground-based instrument; ii) to test the sensitivity of the 2 data acquisition sources in detecting induced variation in N levels. N application gradients from 0 to 250 kg ha-1 were created on 3 different turfgrass species: Cynodon dactylon x transvaalensis (Cdxt) Patriot, Zoysia matrella (Zm) Zeon and Paspalum vaginatum (Pv) Salam. Proximity and remote-sensed reflectance measurements were acquired using a GreenSeeker handheld crop sensor and a UAV with onboard a multispectral sensor, to determine Normalized Difference Vegetation Index (NDVI). Proximity-sensed NDVI is highly correlated with data acquired from UAV with r values ranging from 0.83 (Zm) to 0.97 (Cdxt). Relating NDVI-UAV with clippings N, the highest r is for Cdxt (0.95). The most reactive species to N fertilization is Cdxt with a clippings N% ranging from 1.2% to 4.1%. UAV imagery can adequately assess the N status of turfgrasses and its spatial variability within a species, so for large areas, such as golf courses, sod farms or race courses, UAV acquired data can optimize turf management. For relatively small green areas, a hand-held crop sensor can be a less expensive and more practical option

La propagazione vegetativa di gramigne da tappeto erboso con metodi innovativi

Il successo o il fallimento del tappeto erboso dipendono spesso dalla scelta della specie più adatta alle condizioni climatiche, pedologiche e di utilizzo. Il fattore principale che determina la scelta della specie è il clima. Le specie macroterme sono capaci di vegetare durante i periodi più caldi dell’anno e sono caratterizzate da una stasi vegetativa invernale. Le temperature ottimali di crescita sono comprese fra i 24 e i 32°C per un ottimo sviluppo radicale, e tra i 30 e i 37°C per la crescita di stoloni, culmi e foglie. La loro caratteristica esclusiva è l’entrata in dormienza quando la temperatura scende al di sotto di 10°C. La Cynodon dactylon var. dactylon è l’unica varietà in commercio che produce semi fertili e può essere insediata, oltre che con la propagazione vegetativa, mediante la semina. I vantaggi che questa specie offre per la realizzazione di tappeti erbosi hanno suggerito un approfondimento circa il suo adattamento a diverse latitudini italiane. La tesi da me discussa è articolata in due prove sperimentali. La prima prova, iniziata il 2 febbraio 2010, ha avuto lo scopo di individuare le migliori condizioni di conservazione dei nodi di Cynodon dactylon x transvaalensis cv Patriot, al fine di mantenere il più a lungo possibile la vitalità degli stessi, in termini di percentuale di nodi germogliati. Oltre alla vitalità dei nodi, è stato osservato anche il contenuto in amido. I primi risultati ottenuti hanno dimostrato che i nodi conservati a 6°C hanno una germogliabilità decrescente che si attesta intorno al 30% anche dopo 10 settimane di conservazione e che la concentrazione di amido non è correlata alla vitalità dei nodi. La seconda prova, iniziata il 31 maggio 2010, è stata effettuata presso la sede di Rottaia, San Piero a Grado, Pisa. Sono stati confrontati 44 genotipi di gramigna, comprensivi di ecotipi, cultivars commerciali da seme e cultivars a propagazione vegetativa, provenienti da tutto il mondo, al fine di individuare quelle che meglio si adattano alle condizioni climatiche italiane. I parametri misurati sono stati: copertura del terreno; numero di stoloni per pianta; lunghezza totale degli stoloni per pianta; velocità di crescita degli stoloni pionieri; peso fresco, peso secco, lunghezza e diametro di 10 internodi maturi per pianta. I risultati ottenuti rappresentano un’importante conoscenza di base che può essere utilizzata per migliorare le superfici a tappeto erboso in area mediterranea. La gramigna rappresenta una soluzione tecnica per molte tipologie di coperture erbose e sarebbe auspicabile, visti i risultati conseguiti, una sua ampia diffusione in Italia per la realizzazione di tappeti erbosi di qualità