Determination of critical period of weed control in rice (Oryza sativa L.) in Lorestan province

پژوهشهای زراعی ایران

Article 1, Volume 3, Issue 2 - Serial Number 6, 2005, Pages 171-182   

Document Type: Research Article

DOI: 10.22067/gsc.v3i2.1301

Authors

A Ahmadi^{* 1}; M Rostami²; J Shakarami¹; M Feizian¹

¹-

²Ferdowsi University of Mashhad

Abstract

Effects of different periods of weed control in paddy rice (Oryza sativa L.) were studied in Veysian region of Lorestan province in 2004. The experiment was conducted in a randomized complete block design with four replications and 10 treatments of hand weeding in two series included weed free and weed infested plot up to 14, 28, 42 and 56 days after transplanting, plus weed free and weed infested control. Based on 5 and 10% acceptable yield loses, the critical periods were between 11 to 40 and 14 to 30 days after transplantation, respectively. Weed competition before and/or after these critical periods had negligible effects on grain yield of rice. This period, based on growing degree days (GDD) was 198-768 GDD for 5% acceptable yield loss. Increasing periods of weed interference in the early stage of the crop resulted in a steady decline in grain yield. Yield losses equivalent to 47 kg/ha of grain resulted for each day that weed control was delayed between 14 and 28 days after transplanting.