evaluation of duck efficiency as a biocontrol agent on weed density and diversity in rice-duck farming (oryza sativa l.)

in order to evaluate the effect of ducks number on weeds diversity and density in paddy fields, an experiment was conducted at sari agricultural sciences and natural resource university during growing season of 2011-2012. experiment was arranged in split plot based on complete randomized block design with four replications. main factors were duck number at three levels (consisting of control, 400 and 800 ducks.ha-1) and sub plots were three contrast cultivars (including tarom as a traditional, and shirodi and ghaem as improved cultivars). results of anova showed highly significant differences between ducks, cultivars and ducks × cultivar interaction in terms of weeds density including nutsedge (cyperus spp. l.), common water-plantain (alisma plantago-aquatica l.), barnyard grass (echinochloa crus-galli l.), duckweed (lemna minor l.), azolla (azolla pinata r.br.) and paddy yield. accordingly, the lowest weed density and diversity were recorded at 800 and 400 ducks.ha-1, respectively. among rice cultivars tarom and ghaem had the minimum and the maximum weeds density and diversity. the highest nutsedge density (67 plant.m-2) was related to ghaem cultivar in control (without duck) plots as much as 97% higher than 800 ducks.ha-1. maximum paddy yield was observed in 800 ducks.ha-1 in shirodi (5.3 t.ha-1), ghaem (4.3 t.ha-1) and tarom (3.6 t.ha-1) as much as 23, 7 and 20% higher than those cultivars in 400 ducks.ha-1, respectively. finally, in the current research conditions using 800 ducks.ha-1and tarom cultivar resulted the best performance because of the lowest weed diversity and density as compared to other treatments.