Growth and yield of different types of dry bean affected by smooth amaranth (Amaranthus hybridus L.) shoot extracts

A greenhouse experiment was conducted at the Faculty of Agriculture, University of Tabriz in 2012, in order to evaluate the allelopathic effects of smooth amaranth shoot extracts of some growth parameters, grain yield and yield components of three different types of dry bean. The experiment was conducted as factorial experiment based on randomized complete block design with four replications. Different concentrations of shoot aqueous extracts (0% (control), 5, 10, 15, and 20% w/v) with red, white and pinto bean were arranged in a factorial experiment. The results revealed that aqueous extracts of smooth amaranth affected relative water content (RWC) and both vegetative growth and grain yield of dry beans. All the responses were concentration-dependent. Root growth exhibited higher sensitivity to allelopathic stress over shoot growth. Reduced grain number per plant was mainly caused by reduction in grains per pod. Grain weight had minor drops at varying extracts, compared to grains number. Significant decline in number and size of produced grains led to significant grain yield losses at 15 and 20% extracts. Pinto bean yielded better than the other bean types, hence could be cultivated in cropping systems with high densities of smooth amaranth as a high-tolerant crop to overcome weed problems which reduces dry bean yield loss.