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9 th EWRS Workshop on Physical and Cultural Weed Control 80 Samsun, Turkey, 28 – 30 March 2011 Broadcast flaming in warm-season turfgrasses A. Peruzzi, M. Fontanelli, C. Frasconi, M. Raffaelli, F. Sorelli,. Dipartimento di Agronomia e Gestione dell’Agroecosistema, Università di Pisa, Via San Michele degli Scalzi, 2, 56124, Pisa, Italy aperuzzi@agr.unipi.it An innovative solution for vegetative establishment of warm-season turfgrass species seems to be field planting of seedlings (similar to vegetable planting). This technique is an Italian patent (called “Erbavoglio system”) and gives some of the advantages of sodding (the use of pallets or rolls of pre-established turf) with lower costs. On the other hand, these species, when planted, can suffer from weed competition during the first period of establishment. A long term experiment, started in July 2009, is being carried out with the aim of assessing the tolerance of three different warm-season transplanted turfgrasses to open flame treatments, Zoysia tenuifolia Willd. ex Thiele Cynodon dactylon L. Pers. and Paspalum vaginatum Sw. during the first 5 weeks of development, in the perspective of application of selective thermal weeding interventions. The plants were grown in a greenhouse and transplanted in 30 cm high 23,5 cm wide and 5 cm deep pots, containing peat based substrate. Four plants were hand transplanted in each pot. The thermal treatments were performed with a test bench equipped with a belt conveyor driven by an electric engine, a 25 cm wide rod burner and a LPG feed group that allowed to operate with different values of pressure. LPG dose per unit surface was obtained by combining the different speeds with the different working pressures. For each species different doses and different frequencies of treatment were tested. The frequency of treatment was also differently distributed along the time. Digital images were analyzed with an automated procedure, originally programmed in MATLAB3, and later developed into a web-based software (www.imaging-crops.dk), with the aim to asses crop canopy one week after treatments. Crop biomass was assessed at the end of the cycle. In order to find a relationship between the doses of LPG and the plant cover percentage, non-linear regression was performed fitting a 3 parameters log-logistic model. Biomass loss was described using a yield loss- Michaelis Menten model (“R” software, “drc” package – Ritz & Streibig, 2005). Cynodon dactylon was the most sensitive species showing on average a 50% reduction of the canopy using about 15 kg ha -1 of LPG, a maximum biomass loss of 75% with one treatment and 100% with two or more treatments. Paspalum vaginatum appeared the most tolerant showing on average a 50% reduction of the canopy at about 30 kg ha -1 of LPG, a maximum biomass loss of 65% with one treatment and 100% with two or more treatments. Zoysia tenuifolia showed on average a 50% reduction of the canopy using about 25 kg ha -1 of LPG, while biomass sampling and data processing are still ongoing. However, selective flame treatments seem possible for warm-season turgrasses, if applied with an adjusted dose. This research was funded by the Ministry of Agricultural, Food and Forestry Policies of Italy. Project: “Sistemi avanzati per la produzione vivaistica di tappeti erbosi di specie macroterme ad uso multifunzionale a basso consumo idrico ed energetico”.
9 th EWRS Workshop on Physical and Cultural Weed Control 81 Samsun, Turkey, 28 – 30 March 2011 Can image analysis be a tool to measure changes in vegetation cover after flame treatments? A.M. Rask 1 , P. Kristoffersen 1 & C. Andreasen 2 1) Forest and Landscape, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 23, DK-1923 Frederiksberg C, Denmark and 2) Department of Agriculture and Ecology, Crop Science, Højbakkegårds Allé13, DK- 2630 Taastrup, Denmark. In many countries the risk of pollution of the environment has led to restrictions on the use of pesticides in urban areas, and herbicides are often replaced by flame weeding. Flame weeding controls a wide range of annual weed species, but plant species with protected meristems, such as grass weeds, pose a special problem because of their ability to regrow after the treatment. Therefore, repeated treatments are necessary, which increase the costs. In this study, the changes in vegetation cover of the test species Lolium perenne (L.) (perennial ryegrass) was measured by image analysis during an entire growing season. Measurements of the effect of non-chemical weed control by flaming can be done in several ways. The most used method is to take biomass samples from the experimental plots and dry and weigh the plants. Dry weight of plants gives a useful estimate of the effect of the treatment. If the aim of the investigation is to measure the effect of repeated treatments, the removal of the biomass makes is impossible to measure how regrowth would occur under normal conditions. Additionally it is very labour demanding. Other methods can be used, such as measuring light reflection, visual assessment, or, as in our case, use of image analysis. In the present study, a large number of treatment plots were treated with a gas burner with different doses (0-180 kg gas ha -1 ) and time intervals (2-10 yearly treatments). To measure the treatment effect on regrowth, images were taken every second week (14 days after the last treatment) from May to October 2008. The experiment was repeated in 2010. To avoid camera shaking and to get images of the same size, a camera mounting was used. All images were taken with a Canon EOS 400D (iso speed and shutter speed manually adjusted). Camera position was vertical. To obtain diffuse light on sunny days the camera mounting was covered with nylon material. Inside the “tent” a frame (0.63*0.45 m = 0.27 m 2 ) was placed with a white balancing reference in order to calibrate the colors to different illumination. Three times a year, biomass samples were taken and the results from these data were compared with the results from the image analysis. The data showed that it was possible to achieve full control of L. perenne with flaming, but it highly depended on the number of treatments as well as the dose that was applied. Image analysis can be an easy measurement method of vegetation cover but did not give precisely the same results as biomass measurements, because of overlapping vegetation. However, image analysis was a useful method to get a fairly precise estimate of the effect of the treatments.
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