Abstract

Adding chemical nitrogen (N) fertilizer to dry beans (Phaseolus vulgaris L.) is common, even though they have a symbiotic relationship with N2-fixing rhizobia. Research has shown this practice does not always result in a yield response. The objective of this study was to evaluate the effects of N fertilizer and Inoculant management on dry bean yield, maturation time, nodulation and N₂ fixation.

A series of field studies was set up using variations in the timing and rate of N fertilizer application, bean variety, rhizobia inoculant strain as independent variables. The research was conducted at two different sites located in an arid inter-mountain region of northwest Wyoming. Soil texture at the two sites differed substantially, with one a sandy loam and the other a clay loam to clay. There were slight differences among the treatments. The 'Maverick' bean variety preformed very well with or without fertilizer in soils containing clay. The variety of Focus bean tended to have numerically lower yields than Maverick beans. The average yield difference between the two varieties inoculated was 127.68 kgha^-1which was not significant statistically. The rhizobia study showed similar yields as the N fertilizer, variety and Inoculant study. Applying inoculants to dry beans or the commercial supplement NEB did increase yields above the check treatment. When comparing the inoculated treatment to the zero nitrogen treatment there was a small difference of 73.9 kgha^-1. When beans were planted in sandy soils the yield was lower for all three years. The most notable difference was between the diverse soil textures. Yields were higher in the soils with greater clay content. N management is highly variable in dry bean cropping systems. Site-specific research along with the use of models will help manage dry beans in a more sustainable way.