Abstract :
ABSTRACT: To study the competitive effects of redroot pigweed (Amaranthus retroflexus) and lambsquarter (Chenopodium album) on potato, an additive experiment was conducted in the spring of 2004 and 2005 in split-split plot based on randomized complete block design with 4 replications at the Seed Potato Production Station of RAN in Firouzkooh. Treatments were included 2 weed species in main plots (Amaranthus retroflexus and Chenopodium album), weed density in sub plots (2, 4 and 8 plants per meter of row) and relative time of weed emergence in sub-sub plots (8 and 4 days prior to potato and the same time with potato emergence in 2004 and the same time with potato, 2 and 4 weeks after potato in 2005). Results showed that by inceasing weeds interference, light interception of potato was reduced. So, in 8 plant of lambsquarter per meter of row , potato light interception was reduced 43.3 and 53.5 percent in 2004 and 2005. In third level of redroot pigweed (8 plants per meter of row) reduction of potato light interception was 56.5 and 66.8 percent in 2004 and 2005, respectively. By 2 redroot pigweed per meter of row, RUE of potato increased 2.8 percent in comparison with control. It means redroot pigweed supressd potato by shading. In the first and second levels of density of lambsquarter (2 and 4 plants per meter of row) results were similar. Average of potato RUE were 1.56 and 1.83 g/MJ intercepted PAR (for redroot pigweed treatment) and 1.72 and 1.89 g/MJ intercepted PAR in 2004 and 2005.
