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Optimizing of weed control in Brassica vegetables
Ondra, Michal ; Jursík, Miroslav (advisor) ; Václav, Václav (referee)
Small plot field experiment carried out in 2015 on Demonstration and experimental field of Czech University of Life Science in Prague. Objective of the experiment was get new knowledge of efficiency and selectivity of selected herbicides in kohlrabi. Main objective of the experiment was described of influence of irrigation and use of adjuvant on efficiency and selectivity of herbicides. The kohlrabi was growed from transplant. Herbicides were applicated five days after transplanting. Herbicides were applicated in few variant: separately, with adjuvant, two level of irrigation (basic irrigation 15 mm / intensive irrigation 65 mm). During growing season rained 70 mm. Efficiency and selectivity of herbicides was assessed by estimation method using a percentage scale from 0 to 100 %. Efficiency of herbicides was assessed on weeds: Thlaspi arvense, Chenopodium album and Solanum nigrum. Next objectives were: yield of above ground biomass and market tubers, weight of roots, contain of vitamin C, glucosinolates and herbicide residues in tuber.
Efficiency of herbicide Stomp 400 SC was significantly higher than efficacy of Butisan 400 SC on Thlaspi arvense and Chenopodium album. Intensive irrigation caused higher efficiency. On the other side tank mix of herbicides and combination herbicides with adjuvant caused insignificantly higher efficiency. Butisan 400 SC had the highest effectivity on Solanum nigrum compared to efficacy of herbicide, Stomp 400, but efficiency efficacy of herbicide Stomp 400 SC was sufficient.
Stomp 400 SC demaged kohlrabi more than Butisan 400 SC, especially on plots with intensive irrigation. Herbicide Stomp 400 SC had negative influence on roots. On plots treated by herbicide Stomp 400 SC was showed lower weight of roots about 56 % compared to hand-weeding plots.
Kohlrabi on plots treated Stomp 400 SC with intensive irrigation produced not market weight of tuber (less than 200 g/plant) in harvest time. From these reason, the harvest time must have been put off one week. Residues of metazachlor (Butisan 400 SC) were not detected in tuber. Residue of pendimethalin (Stomp 400 SC) was found on every plots treated by herbicide Stomp 400 SC. Found concentration of pendimethalin was not higher than maximal residue limit (0,05 mg/kg). The highest concentration of vitamin C and glucosinolates was found in tuber damaged by tank mix combination of Butisan 400 SC + Stomp 400 SC. On the other side the lowest concentration of vitamin C and glucosinolates was found in tuber from hand weeding plots, but differences among treatments were not significantly.
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