Appraisal of Species-wise Weed Distribution and Critical Period of Weed Competition in Sorghum at Kolladiba, North Gondar

Abstract

A field experiment was conducted to appraise the species-wise weed distribution and critical period of weed competition in sorghum fields in Kolladiba, North Gondar, under rainfed condition during 2002. A total of 15 treatments comprising 7 increasing weed-free (WF) periods, 7 increasing weed-infestation (Wl) periods and a farmers’ practice were used. Fifteen weeds were observed, ten monocotyledonous and five dicotyledonous. Monocotyledonous weeds (91.6%) were dominant. The density, fresh weight and dry weight of composite weeds decreased gradually and significantly as WF period increased and increased as Wl period increased. When sorghum was grown under season-long Wl, its flowering was delayed by a maximum of 9 days and its maturity by 6 days. Sorghum plant population, plant height, head length, number of tillers and biomass decreased with increasing density, fresh weight and dry
weight of weeds. A grain yield of 89.70% was gained from WF period of upto 60 days after emergence (DAE) and 90% from Wl period of upto 30 DAE. On the basis of a 1% maximum tolerable loss of grain yield for farmers in Ethiopia, the critical period of weed competition in sorghum was 30-60 DAE.