Morphophysiological changes in clearfield oilseed rape as a result of the application of ALS-herbicides and weed competition

The use of herbicides and weed competition can negatively affect crop yield. This study aimed to evaluate the effect of eight ALS-inhibiting herbicides and weed competition on some morphophysiological traits of oilseed rape Hyola 571 CL to determine differential herbicide sensitivity and competition with weeds. Two experiments were carried out in a greenhouse in a completely randomized block design, with four replicates. Inexperiment I, imazethapyr, imazamox, imazapic+imazethapyr, imazapic+imazapyr, pyroxsulam, and nicosulfuron decreased the photosynthetic rate of oilseed rape at first, which was later recovered. On the other hand, metsulfuron-methyl demonstrated phytotoxicity in oilseed rape and caused a marked decrease in the evaluated morphological variables. In experiment II, altered morphophysiological traits of oilseed rape were observed, with decreasing values after imazamox application and in the presence of ryegrass and/or turnip. Imazamox reduced gas exchange values after seven days, which did not affect morphological traits of oilseed rape plants after 21 days. However, the competition of oilseed rape with ryegrass+turnip caused a drastic decrease in photosynthesis rate, water use efficiency, and morphological traits. Imazethapyr, imazamox, imazapic+imazethapyr, imazapic+imazapyr, pyroxsulam, and nicosulfuron should be studied in other cultivars but showed potential to be used in weed control in oilseed rape. Competition with ryegrass and turnip was more harmful to the oilseed rape than the initial phytotoxicity caused by the herbicide imazamox.