Evaluation of Sprayer Type Effect and Tribenuron-Methyl (Gyahstar) Herbicide Dosage on Broadleaf Weeds of Water Wheat Fields

Weed management is a key topic in many farming systems. Nowadays, application of herbicides is the most common method to control wheat weeds and maximize yield. Modification of sprayer such as adjusting sprayer for producing droplet with suitable size and uniform can be considered to reduce herbicides usage. For this purpose, the volume median diameter (VMD), numerical median diameter (NMD) and uniform spraying ratio (VMD/NMD) = QC are the common factors. Other method to decrease herbicide usage in field is applying appropriate sprayer. Electrostatic, lance tractor, microner, atomizer and boom sprayer tractor are the common sprayer applying for controlling weeds in wheat fields. Among them, lance tractor sprayer is used at more than 70% of farms in the country. Tribenuron-methyl is a selective post-emergence herbicide for controlling broad leaved weeds in wheat fields. The product is absorbed and transferred by weeds stems and leaves to prevent cell division and kill weeds. Application should be carried out in early spring when weeds are actively growing. Tribenuron-methyl mode of action is inhibiting biosynthesis of the essential amino acids valine and isoleucine, hence stopping cell division and plant growth. Selectivity derives from rapid crop metabolism. Mode of action is rapidly absorbed by foliage and roots and translocated throughout plant. Susceptible plants cease to grow almost immediately after post-emergence treatment and are killed in 7-21 days. To evaluate common sprayer and different doses of tribenuron-methyl herbicide on broadleaf weeds of irrigated wheat, an experiment was carried out in field (with an area of 1200 m2) located in Hakimabad, Mashhad, Iran (latitude 58° 53' N, longitude 36° 46' E) during spring of 2014. The experimental design was split plots based on randomized completed blocks with four replications undertaken in plots with 50 m2 (5 × 10) area. The experimental treatments included the main factor with five types of sprayer (Electrostatic, Lance tractor, Microner, Atomizer and Boom sprayer tractor) and sub factor with applying tribenuron-Methyl herbicide (Giahstar, 75% DF, Ariashimi, Iran) at dosage of 15, 20 and 25 gr. ha-1. Broadleaf weeds were sampled in middle of the plots using 1 × 1 quadrate 10 and 20 days after spraying. The weeds biomass and density and wheat yield loss were then assessed. Samples were oven-dried at 75 °C for 72 h and then weighed. Final data were analyzed by SAS 9.1 and EXCEL. The results of experiment showed that both weeds density and weight were sigificantly reduced by boom sprayer, whreras the lowest efficiency was found for atomizer and lance sprayers. Further, wheat broadleaf weeds were better controlled by boom sprayer with 25 gr/ha tribenuron-methyl application resulting in an increase to 5050 kg/ha for wheat yield. As for solution consumption rate in one hectare, the difference between spraying methods was significant at level of 1%. The highest and lowest herbicide solution rates were found for tractor lance sprayer and microner with 732.8 and 34.9 l.ha-1, respectively. Quality coefficient (VMD/NMD) also was significant at 1% probability level. The best quality coefficients were obtained for tractor boom sprayer (VMD/NMD = 1.8) followed by microner (VMD/NMD = 3). In other words, the tractor boom sprayer had more uniform spray quality than the microner sprayer. Moreover, both sprayers displayed better performance as compared with other sprayers tested. The largest (14.5 %) and lowest (2.8 %) crop losses were determined for tractor boom and microner sprayer, respectively. The highest (3.2 ha-1.h ) and lowest (1.1 ha-1.h ) field capacities were also obtained for tractor boom and microner sprayer, respectively. The microner sprayer was the best sprayer in terms of solution consumption rate with an efficacy rate of 96 %. The greatest wheat yield (4830 kg.ha-1) was observed for tractor boom sprayer with applying 25 kg.ha-1 herbicide. Using tractor lance sprayer applying 15 kg.ha-1 herbicide, however, resulted in the lowest wheat yield (4615 kg.ha-1). The greatest and lowest weeds controls were also found for tractor boom and tractor lance sprayer, atomizer sprayer tractor, respectively. Tribenuron-methyl application with dosage of 25 kg.ha-1 was the suitable dose for controlling prennial weeds such as bindweed, knotweed, knapweed and rhubarb.