Efficiency of Herbicides at Reduced Rates and its Integration with Mulch for Weed Control in Tomato (Lycopersicon Esculentum)

To study the effect of different weed control methods in tomato، an experiment was conducted as completely randomized block design with three replications at the research farm of University of Tehran (Karaj) in 2008. The treatments consisted of post emergence (at recommended rate) or pre emergence (reduced rate in combination with mulch) application of metribuzin، rimsulfuron and sulfosulfuron، and also different binary combinations of these herbicides which applied post or pre emergence (in combination with mulch)، metribuzi+haloxyfop-methyl، trifluralin+metribuzin، and also mulch alone، weed free and weedy checks. Traits such as weed density and biomass، tomato fruit yield and biomass were evaluated. The results showed that only post emergence application of sulfosulfuron (92%)، sulfosulfuron+rimsulfuron (93%) controlled bindweed effectively. However، all herbicide treatments provided good (more than 80%) to excellent (more than 90%) control of redroot pigweed، smooth pigweed and common purslane. Tomato response to rimsulfuron، sulfosufuron and mtribuzin consisted of chlorosis in new terminal growth that recovery occurred after 4 weeks. The results suggest that acceptable control of different weed species in tomato could be obtained by pre-emergence application of rimsulfuron، sulfosufuron and metribuzin in combination with either mulch or post-emergence herbicide.