بررسي اثرات رقابتي سورگوم دانه اي (Sorghum bicolor L. Moench) بر توليد بذر و زيست توده تاج خروس (Amaranthus retroflexus)

Investigating grain sorghum (Sorghum bicolor L. Moench) competitive effects on pigweed (Amaranthus retroflexus) seed and biomass yield

In order to predict competitive effects of redroot pigweed on yield and yield components of grain sorghum by observation of relative leaf area an additive series experiment (response model) with factorial in randomized complete block design were conducted in 2005 growing season at Research Farm of Khorasan Agriculture and Natural Resources Research Center. Two factors were involved in the experiment, redroot pigweed density in four levels (0, 2, 8 and 16 plant/m2) and sorghum density in three levels (10, 15 and 30 plant/m2). Investigation about the pigweed growth index showed that sorghum and pigweed density was significant (p<0.01) on pigweed biomass. Pigweed seed and biomass production was affected by competition between sorghum and pigweed. The highest pigweed biomass was obtained at minimum sorghum density and with increase sorghum density pigweed biomass decreased. Maximum pigweed seed was produced at the same sorghum density where pigweed biomass was maximum. A alometric relation showed that minimum biomass pigweed needed for seed production in pigweed is 3.88 g/plant.