The Effet of Weed Infested and Weed Checkon on Growth Properties and Yeild of Corn (Zeamays L.)

Weed management systemis a successful approach to reduce weed control cost and gain an acceptable economic performance. Therefore, this study was carried out based on randomized complete block design with four replications in Agro-industry field Dashtenaz Sari, during 2010 to evaluate the effect of weed control and its interference on corn growth properties. Treatments including weed free and weedy check(infested)along with free weed and weedy infestedat 3, 6, 10, 14 were applied with leafy stage tasseling.Logestic non-liner equation was used for critical period of weeds control at start and end of the time.The result showed that most dominant weeds were velvetleaf (Abutilon thophrasti) and pigweed (Amaranthus retroflexus).The interference period did not have significant effect on dry weight and height of weeds; whereas, The control period has significant effect on density of weeds.The interference and control periods did not show significant effect on corn height; whereas, a significant relationship was observed with stem diameter, dry weight, ear length, ear diameter, ear weight, number of kernel rows per ear, number of kernels per row, thousand kernel weight and corn yield. Weed interference compared to weed free showed reduction instem diameter, dry weight, ear length, ear diameter, ear weight, number of kernel rows per ear, number of kernels per row, thousand kernel weights and corn yield. Critical period of weeds was estimated between38-65 days after corn planting or 392-804 GDD (7-8 leaf stage) stage to tasseling at 5% levels reduce seed yield, and at 10% levels reduce seed yield, critical period was estimatedbetween 48-55 days after corn plantingor 534-653 GDD.