KRITIČNO RAZDOBLJE ZAKOROVLJENOSTI U PROIZVODNJI SOJE NA PODRUČJU VUKOVARSKO-SRIJEMSKE ŽUPANIJE

Weeds are unwanted plants on our fields and they have negative effect on crop yield. One of the main goals in agricultural production should be sucessful weed control without having negative economic impact on crop production. To acomplish this task it is crucial to know the floristic composition and timing of the critical period of weed removal from the fields. Thirty four weed species were determined on the experimental plots, but only four dominated during the whole study period (2014.-2016.) and in all row spacings (25 cm, 50 cm and 70 cm). They are: Amaranthus retroflexus, Chenopodium album, Setaria viridis and Sorghum halepense. However, in soybean weed community Sorghum halepense (2014. and 2015.) and Chenopodium album (2015. and 2016.) reached the highest totoal relative abundance. Critical period of weed removal were significantly different in all row spacings and study years. For acceptable 10% yield loss CPWR ranged from V1 to R7, and for 5% acceptable yield loss it was ranged from VE to R7. According to this investigations we can reccomend soybean (middle early variety) planting in 70 cm rows with two interrow cultivations. However, on highly infested fields it is necessary to have pre-em or post-em chemical application, but on less infested fields weeds could be sucessfully controled with post-em application.