Impact of Time and Rate of Imazetapyr Herbicide Application on Growth and Yield of Faba bean (Vicia faba L.)

To evaluate the effect of time and rates of imazethapyr application on weed control of bean field an experiment was conducted in Agricultural Research Station of Lorestan University based on the randomized complete block design (RCBD) with three replications in 2015-2016. In this experiment, the effects of pre planting, pre emergence and post emergence applications of imazethapyr with different rates (0.25, 0.5, 0.75 and 1 lit.ha-1) and pre planting imazethapyr mixed with soil (1 lit.ha-1) plus post emergence with weed control in two levels (control and non- control) was studied. The most important weed species in the experimental site were safflower (Carthamus oxyacantha), catchweed bedstraw (Galium tricornutum), wild mustard (Sinapis arvensis), cow cockle (Vaccaria grandiflora), chickweed (Conringia orientalis). Weed density in weedy control condition was estimated to be 133 plants.m-2. The results showed the maximum percentage of weed dry weight loss, as compared to not controlling weed due to imazetapir post-treatment application of 0.75 and 1 L.ha-1, was 86.95%. Also highest average root length (12.46 cm), root dry weight (95 g), number of branches (5.33), number of seeds per pod (9.3) and seed yield were observed in hand weeding. The highest plant height (88.33 cm) belonged to weed control treatment, the highest LAI (2.59) in herbicide usage, in pre planting (0.25 lit.ha-1), the highest average number of pod per plant (10 pod), number of pod per m-2 (100 pod) and biological yield (33367.1 kg.ha-1) resulted from pre emergence herbicide application (0.5 lit.ha-1). The highest of 100 seed weight (109.6 g) for pre planting herbicide application (1 lit.ha-1) plus herbicide post emergence application (1 lit.ha-1) was seen. The results also showed that, after hand weeding, the best concentration of imazethapyr pre emergence application (0.5 lit.ha-1) that it could decrease weed density by 99% as compared to not controlling weed. This treatment (imazethapyr pre emergence application (0.5 lit.ha-1) was the best treatment. Higher concentrations of herbicides also decreased bean yield because of burning, reduction in leaf area and photosynthesis.