investigating the possibility of reducing herbicide application in corn (zea mays l.) by using density and planting pattern

in order to study the effects of corn density and planting pattern for reducing herbicide application, an experiment was carried out in 2007 at varamin research station of plant protection research institute. the experimental design was a randomized complete block in a split plot arrangement with 4 replications. experimental factors consisted of planting patterns at 4 levels included one row planting on each ridge with recommended density, two rows planting on each ridge with recommended density, 0.25 and 0.5 times more than recommended density in main plots and herbicide at 5 levels including atrazin 1 l/ha plus eptc 4, 5 and 6 l/ha, atrazin 1 l/ha plus allachlor 5 l/ha, eptc 6 l/ha in subplots. weed-free and weedy controls were added to treatments. results indicated that altering planting pattern to two rows planting with 0.25 and 0.5 times more than recommended density significantly increased grain yield. grain yield of herbicide treatments except weedy control had no significant difference in comparison with weed-free control. therefore by using reduced rates of herbicides it is possible to decrease herbicide application. herbicide application had significant effect on number of kernel rows per ear, 100-grain weight and ear diameter and grain yield was increased.