M.A. Thesis:

If and physiological reaction of maize varieties with different groups dealing with reduced amounts of nicosulfuron herbicide

Abstract In order to investigate the agro physiological response of corn varieties with different maturity groups to low dose of Nicosulfuron (cruise) herbicide, a split plot design with a randomized complete block design with three replications was carried out in Barekat Jovain Agricultural Company in 2017. Factors were: Corn cultivar (Early (260 single cross hybrid, Medium (400 single cross hybrid) and Late Maturing ( 704 single cross hybrid) varieties as main plot and subplots were five herbicide dose (0 (weedy), 25, 50, 75 and 100% Recommended dose (60 g.ha-1 a.i. Nicosulfuron) and with one weed free treatment. The results of the experiment showed that there was no significant difference among cultivars in terms of most of studied traits, however, the late cultivar had more plant height, ear weight, number of rows per cob, number of seeds per row, cob weight, and seed number in cob, economic yield, biological yield, weed density and weed dry weight than other cultivars. Increasing doses of herbicide increased plant height (0.64%), ear weight (39.45%), number of rows per cob (8.93%), number of seeds per row (30.15%), seed weight (10.68%), number of seed per cob (40.63%), economic yield (41.82%), biological yield (14.95%) and decreased weed density (70.88%) and weed dry weight (82.17%) compared to weedy treatment. The use of the recommended herbicide dose has the same effects as weed control. 75% of the recommended dose in all three varieties produced the same yield as the recommended dose. But in the late maturity cultivar, the 50% reduction in recommended doses could be similar to the recommended dosage. In general, it can be said that increasing the length of the plant growth period allows the use of doses lower than the recommended dose.

Keywords: Herbicide, Maize, Maturing group, Yield, Weed.