The study of additives on the efficacy of herbicides of Othello, Topik+ Granstar, Total and Apirus in controlling of wild oat and charlock mustard as dominant weeds of wheat

Adding an adjuvant facilitates the uptake of herbicides through the aerial parts of plants and reduces the selective state of the herbicide. If the amount of adjuvants is more than the amount needed to moisturize the surface of the plants, the penetration of herbicides will increase. The experiment was conducted to determine the best additives on increasing the effectiveness of herbicides in controlling wheat weeds.

The experiment was conducted in a randomized complete block design with three replications in a farm in Fasa (28° 56' N, 53°38′E) during 2017-2018. The factors consisted of herbicides in four levels of Mesosulfuron+ Iodosulfuron+ Diflufenican (Othello), Clodinafop Propargyl (Topik)+ Tribenuron–Methyl (Granstar), Sulfosulfuron+ Metsulfuron Methyl (Total) and Sulfosulfuron (Apirus) in recommended doses and type of additives in 4 levels, Ammonium Sulfate 2%, soybean oil 1.25%, cleaner liquid as surfactant Anionic 0.5% and without additive as control. Wheat seeds of Chamran cultivar with vigour of 98% at rate of 150 kg.ha-1 were planted in rows of 10 cm. The dimensions of each experimental plot were 24 m. Herbicide application time was also in the wheat tillering and 2-4 leaf weeding stages. The experimental sprayer was used with a manual pump, with a nozzle with a spray angle of 30 degrees, a constant pressure of 50 psi and a spray height of 20 inches (50 cm) calibrated for spraying. Characteristics such as dry weight of narrow weeds include wild oat (dominant weed) along with canary grass and Ryegrass, broad-leaf weeds include charlock mustard (dominant weed) along with fumitory was determined. Number of spikes per square meter, number of seeds per spike, 1000 grain weight, biological yield, grain yield and wheat harvest index were measured.

The results showed that among the additives used, 2% Ammonium Sulfate had the greatest effect on reducing the dry weight of weeds, narrow-leaf (34.05%) and broad-leaf (31.57%) weeds. The herbicides of Othello, Topik+ Granstar and Total had performed well on wheat grain yield, but did not show significant differences. The combination of additives with herbicides compared to no adjuvant control increased grain yield (on average, 607.73 kg.ha-1). Finally, Othello herbicide was introduced as the best treatment for this test by consuming 2% Ammonium Sulfate additive.

The effect of herbicides application of Othello, Topik+ Granstar and Total on grain yield can be due to their effect on decrease of weed dry weight. The results show that ammonium sulfate 2% increased the uptake of herbicides and which is why it increases the effectiveness of herbicides in weed control and grain yield increase.