Effects of six herbicides on toxic weeds in cultivated grasslands in the source region of the Yellow River

A 14-year-old cultivated grassland of Elymus nutans in Maqin County, Guoluo Prefecture, the source region of the Yellow River, was investigated. Pedicularis kansuensis and Ligularia virgaurea were the research objects. To control the main broad-leaved toxic weeds, six herbicides, individually and in five combinations, were tested. The six herbicides were 2, 4-D butyl ester (A), trituron (B), Longquan (C), Kono (D), Chakuo (E), and Tribenuron (F); and the five combination were 2, 4-D butyl ester and each other herbicide, namely, A + B, A + C, A + D, A + E, and A + F. Spraying B, F, and A + E reduced the height, cover, and biomass of L. virgaurea to varying degrees, and F and A + E had significant effects on biomass (P < 0.05). Spraying E, F, A + B, A + C, and A + F significantly reduced the height, cover, and biomass of P. gansuensis (P < 0.05), with A + F effectively controlling the toxic weed community. The highest control level was level 3. The cover and biomass of forages under A + E treatment were significantly higher than those of the control (P < 0.05). The species richness and Shannon-Wiener index of the herbicide-sprayed communities generally showed a downward trend. However, the uniformity index was slightly higher than in the control. The effects of the 11 treatments were evaluated using the fresh weight control effect, and the results showed that A + E, F, and A + F can control toxic weeds in cultivated grasslands in the source area of the Yellow River.