engleski

Impact of tillage systems and herbicides on weeds and soybean yield

Field experiments (2009-2010) were carried out in soybean on lessive pseudogley soil in north- eastern Croatia to evaluate the impact of three continuous tillage systems (conventional with mouldboard ploughing, chisel ploughing, disk harrowing) and chemical weed control through split application of post-emergence herbicides at reduced rates alone or in combinations, on weed density, fresh weed biomass and crop yield. Total weed density in untreated plots was significantly influenced by tillage and it was the highest in disk-harrowing (202.0 plants m-2), medium in chisel ploughing (126.5 plants m-2) and the lowest in mouldboard ploughing (109.3 plants m-2). In comparison with conventional tillage, chisel ploughing and disk harrowing increased weed number on average by 15% and 85%, respectively, after only two years of experiment. The main weeds were annual species of Echinochloa crus-galli (L.) PB., Ambrosia artemisiifolia L., Chenopodium album L., and Polygonum lapathifolium L. with a share of 89% and 83% of the total weed population and biomass, respectively. The efficacy of herbicide treatments in the control of main weeds did not vary significantly between tillage treatments. The best and equal total weed biomass reduction of 96% was provided by both herbicide combinations of imazamox 24 g + oxasulfuron 50 g plus thifensulfuron-methyl 6 g a. i. ha-1 and of oxasulfuron 60 g + oxasulfuron 60 g plus thifensulfuron-methyl 4 g a. i. ha-1, whereas the treatment with imazamox 24 g + 24 g a. i. ha-1 reduced the weed biomass by 93%. Weed control had no impact on soybean yields that were significantly affected by year and tillage. Compared to the highest yield with mouldboard ploughing (4183 kg ha-1), the average percent yield decreases with chisel ploughing and disk harrowing were 6% and 14%, respectively.

soybean ; tillage systems ; imazamox ; oxasulfuron ; thifensulfuron-methyl ; weed density ; weed biomass ; crop yield

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