Competition of redroot pigweed (Amaranthus retroflexus L.) and nettle-leaved goosefoot (Chenopodium murale L.) with tomato (Lycopersicon esculentum Mill.) cultivars

Competition of 31 tomato (Lycopersicon esculentum Mill) cultivars with Amaranthus retroflexus and Chenopodium murale was investigated at different growing periods under natural conditions, University of Jordan, during 2008–2010. Cultivars were varied in their competitiveness with weeds; some tolerated while others were highly susceptible and exhibited great growth (shoot dry weight) and fruit yield reductions. A. retroflexus was more competitive than C. murale at most growing periods. Weeds attained high growth in the spring and summer but were much reduced in autumn. A. retroflexus requires relatively higher temperature for growth and competitiveness than C. murale. Gardners Delight and Special Back cultivars showed tolerance and their growth and yield either increased or least reduced in competition with weeds. In contrast, growth of First in the Field, Back More, Orient and Tiny Tim was reduced by 65–75% of their controls. Highest growth of weeds was in competition with The Amateur and lowest with First in the field and Back More. Fruit yield of all cultivars was reduced in competition, especially with A. retroflexus. Reduction was up to 100% in the spring. Both weeds reduced growth of cultivars most during the spring while A. reteroflexus eliminated certain cultivars.