Efficacy of soil herbicides in controlling common ragweed depending on the amount and the number of days after herbicide application

The effectiveness of 12 pre-em herbicides in controlling ragweed was studied: atrazine, alachlor, acetochlor, alachlor+linuron, S-metolachlor, pendimethalin, metribuzin, prometryn, napropamide, imazethapyr, oxyfluorfen and dichlobenil. The research was conducted over two years, where the herbicides were applied in May on soil that had been prepared for sowing, but not sown. The efficacy was observed 30, 45 and 60 days after the application. Herbicides were used in 4 different doses: D1 which is ½ of the recommended dose, D2 is the lowest recommended dose, D3 is the highest recommended dose and D4 is the dose where the herbicides were used with the dose higher than it is recommended (D3×1,5). Efficacy is expressed as the percentage of efficacy for the number and fresh weed biomass, compared to the control. Coefficient of multiple correlation between the percentage of efficacy (PE), as a dependent variable, and the dose (D) and the number of days from the application of herbicides (DAA), as independent variables is statistically significant and in all cases it ranges between 0,853** and 0,961****. Partial correlation coefficient of efficacy percentage dependent on the herbicide dose is positive and in almost all cases highly significant, varying from 0,739** to 0,956****. Partial correlation coefficient between the herbicide efficacy percentage for common ragweed biomass and time after herbicide application is negative and statistically significant, or highly significant and varies between -0,606* and -0,904***. The partial correlation coefficient of the herbicide efficiency percentage for the common ragweed plant number and days after herbicide application, is also negative and varies, depending on the herbicide, between -0,182NZ and -0,923****.