Research regarding the control of dicotyledonous weeds in rapeseed crops, in Calarasi County.
Rapeseed crop is one of the most profitable agricultural investments, very wide opened to development in Romania. In the latest years, rapeseed has been cultivated on larger surfaces, as this plant may produce quality oil. It is also known as a biodiesel plant, more and more requested for fuel, so that the total area cultivated with rapeseed was 632 thousand ha in 2018. Of this surface, 63,389 ha were grown in Calarasi County. New agricultural technologies and new hybrids have allowed it to grow successfully under our country's climatic conditions. Beside of this, this crop has its own particularities that must be carefully taken into consideration in order to obtain high yields. To give best results, rapeseed needs to be carefully protected, just because this plant can hardly bear weeds infestation, which is one of the limiting factor of yield. In recent years, due to weather evolution, with very mild winters, many weeds species (Galium sp., Lamium sp., Matricaria sp., Thlaspi arvense, Veronica sp., etc.) have grown, even propagated, so that they became a problem more and more often. On the contrary, under normal winter conditions, even during freezing winters, this fact would have never happened. These weeds, among which some invasive species (Veronica persica) become immune to the cold and enter the spring well-developed and compete with the crops for water, air, light and nutrients. In this context, the paper reveals aspects regarding the control of the annual and perennial dicotyledonous weeds in the rapeseed crop grown in two distinct locations in Calarasi County, where post-emergence treatments with clopyralid herbicides formulated in the form of a soluble concentrate (SL) and of water soluble granules (SG) were applied in spring. Herbicides were applied at different rates and at different crop and weeds stages. The assessments concerned the effectiveness in control, the safety of the crop as well as a comparative analysis between the two formulations SL vs. SG respectively, regarding the mode of action on weeds and the level of weeds control. The research results indicated that clopyralid-based herbicides had good efficacy in controlling dicotyledonous weeds depending on the rate applied, the time of application and the degree of weed infestation.