Phosphorus Fertilization and Symbiotic Nitrogen Fixation in Common Bean

Abstract

AbstractSoils in the major bean (Phaseolus vulgaris L.) producing regions of Latin America are frequently deficient in both P and N. With the fertilizer available to small farmers limited, the appropriate strategy for efficient fertilizer use could depend on the relative P requirements for plant and nodule development and N fixation in this species. In this field study the objective was to examine the growth, P distribution, and parameters of N2 (C2H2) fixation of bean cultivars at different levels of P fertilization.Seeds from 30 bean cultivars (replicates) were inoculated and lime pelleted, then sown into a Typic Dristandept soil low in available P. Phosphorus fertilization from 0 to 315 kg/ha as triple superphosphate was applied, then plant and nodule development, P distribution and N2 (C2H2) fixation measured 42 days after planting.Nodules were a strong sink for P, nodule weight increasing ninefold and P concentration in nodules by almost 50% over the range of P fertilization used. Other plant tissues benefited less. Levels of N2 (C2H2) fixation , specific nodule activity, and non structural carbohydrate in nodules were highly correlated with supply of P.Though P concentration in nodules reached 0.27%, there was no indication that the maximum fertilization rate used was adequate for full nodule development or nitrogen fixation. Further, none of the 30 cultivars tested showed reasonable N2 (C2H2) fixation at low rates of P fertilization. It may be concluded that identification of bean cultivars able to grow at low P, but still efficient in Na fixation, will be difficult.