Estimation of economic thresholds for weed control in corn (Zea mays L.) by mechanical, chemical and integrated methods

This present research was arranged to determine economic thresholds of three weed species in corn field including redroot pigweed، purslane and Johnsongrass. The control methods were chemical، mechanical and integrated method. The statistical design was a randomized completely block with eleven treatments in 3 replicates. The experiment was conducted at the experimental station of Agricultural and Natural Resources College of Darab، Shiraz University، in 2004 and 2005. The treatments included the application of Atrazine plus Alachlor at 1+2. 5 and 0. 5+1. 25 kg ai ha-1 used as broadcast and band application alone and in combination with rotary or sweep cultivators and mechanical weeding alone. The Results indicated that the economic thresholds in Johnsongrass was controlled by chemical، mechanical and integrated methods were 4. 371، 7. 270 and 10. 164 weed/m2 respectively. The economic thresholds of Purslane were 1. 185، 2. 104 and 1. 624 weed/m2 respectively and for the Redroot pigweed were 2. 816، 4. 886 and 3. 932 weed/m2 respectively. Furthermore’ based on the economic threshold، mechanical weed control which is an early control method should be applied. Otherwise another appropriate control method based on the plant density as envisaged by economic threshold should be considered for each weed specie.