Effect of plant density and manure application rate on yield and yield components of various common bean (Phaseolus vulgaris L.) cultivars

Phaseolus vulgaris or common bean, is an herbaceous annual plant in the Fabaceae is cultivated in many parts of the world. Bean varieties have been developed to have both bush and twining forms. Numerous cultivars of common beans have been developed, including string beans, stringless varieties (such as the slender French haricot varieties), and snap beans. Intensive agricultural activities have led to profound land use transformations. As a result of intensive successive croppings, there has been physical, chemical, and biological degradation of soils, resulting in decreased crop productivity. This trend is incurring high economic and environmental costs. The use of organic fertilizers, such as animal manures has been proposed as one of the main pillars of sustainable agriculture. Animal manure is a valuable resource as a soil fertilizer because it provides large amounts of nutrients for crop growth and is a low-cost, environmentally friendly alternative to mineral fertilizers. The environment within a canopy of given density will be affected both by plant architecture and row spacing. As seed is a major input cost for dry bean production, optimum plant density should maximize yield while minimizing seed cost. Solutions based on the principles of ecological agriculture in agricultural ecosystems, in addition to the current needs of the plant, also lead to long-term sustainability of agricultural systems. To evaluate the yield and yield components of common beans by planting density, manure and cultivar, a factorial layout based on randomized complete block design with four replications was conducted at the Agricultural Research Station, Ferdowsi University of Mashhad during growing season 2014-2015. Experimental factors including cow manure levels, three levels (0, 15 and 30 t.ha-1), plant density on row, three levels (5, 10 and 15 plants.m-2) and cultivar, three levels (Akhtar, D-81083, Naz and Goli). Before harvesting, plant height, pod number per plant, seed number per pod, seed weight per pod and 100-seed weight were measured in 10 randomly selected plants. Biological and seed yields of bean were determined at the end of growing season. Studied traits were plant height, pod number per plant, seed number per pod, seed weight per pod, 100-seed weight, seed yield, biological yield and harvest index (HI) of bean. Analysis of variance (ANOVA) and least significant difference were performed using SAS version 9.3 (SAS Institute Inc., Cary, NC, USA). The results showed that the simple effects of manure, density and cultivar were significant (p≤0.05) on more studied traits of bean. By increasing manure level yield and yield components of bean were enhanced. By increasing manure level up to 15 and 30 t.ha-1 seed yield was improved due to improvement in physical and chemical characteristics of soil up to 7 and 15% compared to control, respectively. Also, by enhancing plant density an increasing trend for yield was observed. In comparing different cultivars the highest seed yield was observed for Naz (291.04 g.m-2) and the lowest was for Akhtar (236.63 g.m-2). The maximum seed yield was related to 30 t manure per ha-1 + Naz (305.59 g.m-2) and the minimum was for control +Akhtar (220.33 g.m-2). Seed yield had positive correlation with plant height, number of pod per plant, number of seed per pod, seed weight per pod and 100- seed weight and the highest correlation coefficient was computed for 100-seed weight (R2=0.723**). Genetic potentials between cultivers created differences in yield and yield components, so the highest yield among cultivars was obtained by Naz. By increasing manure level seed yield and yield components were enhanced due to improvement in physical and chemical characteristics of soil. By increasing plant density up to 20 plants.m-2 seed yield of bean was increased. The highest yield among cultivars was obtained by Naz.