Effect of rhizobium inoculation, molybdenum and lime on the growth and N2 fixation in P. vulgaris L

Abstract

The study used common bean (P. vulgaris L. variety Provider) in a spilt-split-plot design involving 2 levels of Rhizobium inoculation (with and without rhizobia), 3 levels of lime (0, 2 and 3 t.ha-1) and 3 levels of molybdenum (0, 6 and 12 g.kg-1 of seeds) in a glasshouse experiment. The glasshouse experiment was then verified in the field during 2008 and 2009 cropping seasons. The aim was to assess the effects of Rhizobium inoculation, molybdenum and lime supply on: i) yield and yield components of the P. vulgaris L. ii) Changes in soil pH and the concentrations of selected plant-available nutrients in the rhizosphere, iii) photosynthesis and chlorophyll formation in P. vulgaris L. and (iv) plant growth and N2-fixation in P. vulgaris L.

The results showed that Rhizobium inoculation had significant effects in increasing yield components and ultimately the final seed yield. Rhizobial inoculation also significantly increased the levels of chlorophyll content in leaves, improved all photosynthetic parameters, increased dry matter yield of different organs and decreased 15N values in all organs assessed. As a result, % nitrogen derived from atmosphere (%Ndfa) in all organs as well as the amount of N derived from fixation was improved. In the field, the whole plant level of N-fixation of P. vulgaris L. from Rhizobium inoculation accounted for approximately 33 kg N.ha-1. Furthermore, soil pH and the concentration of mineral nutrients (P, K, Ca, Mg, Na, Fe, Cu, Zn and Mn) in the rhizosphere were significantly increased with Rhizobium inoculation when compared with the control.