Abstract
The purpose of this study was to determine the effect of different weed competition periods on the growth and yield of an Egyptian barley crop under field conditions, as well as to estimate the critical period of weed control (CPWC) in barley. The treatments were arranged in a randomized complete block design with three replications (i.e., plots 4 x 4 m each) and consisted of a quantitative series of both increasing duration of weed interference and length of weed-free periods. The measured morphological parameters of barley plants were greater in non-weedy barley fields than in weedy barley fields. The shoot height of non-weedy barley plants was significantly (P < 0.05) higher than that of weedy plants. After 75 DAE (Days After Emergence) of weed infestation, the maximum height and plant density were obtained. The biomass of barley plants and their associated weeds was gradually increased until 45 DAE, when barley biomass continued to increase, while weed biomass decreased. The maximum barley yield in the weed-free plots was 3.2 t ha-1 after 90 DAE, while it was 2.2 t ha-1 in the weed-infested plots after 75 DAE. Based on a 10% yield loss, the CPWC fell between 63 and 79 DAE, while a 5% yield loss fell between 41 and 102 DAE. Weed presence prior to and after the CPWC is not expected to reduce crop yield. As a result, weed removal at the CPWC is critical to allow plants to grow to their full potential without being hampered by competition and, hence, crop yield loss.