Interactions of Herbicide Doses and Application Time on Sorghum halepense Control in Maize (Zea mays)

A field experiment was conducted to determine the interaction effects of herbicide timing and doses on the control of Sorghum halepense in maize. The experiment was a split plot in randomized complete block design (RCBD) with three replications. Main plots were herbicide doses (0, 40, 60, 80, 100 g.ae of nicosulfuron) and sub-plots comprised herbicide timing (maize growth stages: 2-4 leaves, 4-6 leaves and 6-8 leaves). Standard dose response model was used to describe the relationship between weed biomass and herbicide doses at each herbicide application time. Estimated parameters showed that herbicide application delay increased U, L, ED50, ED90 parameters linearly. The highest yield of maize (20478.8 kg/h) was obtained by 2.5 lit/ha herbicide applied at 2-4 leaves of maize growth stage. Recommended dose of herbicide resulted in 12108.74 kg/h maize yield when it was applied at 6-8 leaves maize growth stage. In summary, 1.5 lit/ha herbicide applied at 2-4 leaves growth stage of maize gave acceptable control and decreased S. halepense biomass from 144.9 to 41.2 g/m2. The respected amount of weed biomass was not able to compete with maize and make damage. Results of the current study can be used in S. halepense management programs in maize fields.