Title : Relationship between phosphorus status and nitrogen fixation by common beans (Phaseolus vulgaris L.) under drip irrigation
The current study aims to examine, the response of contrasted recombinant inbred Lines (RILs) of common bean to the application of phosphorus (P), to identify the bean RILs which were efficient in P utilization when dependent on N2 fixation as a source of nitrogen. The experiment was conducted at the experimental farm of Agricultural Research Station of the Nubaria district, Behera, Egypt, during the winter seasons 2008-2009.Three levels of mineral phosphorus (P) fertilizers were applied (0, 45 and 90 kg P2O5 ha-1). Nodulation, plant growth parameters, leaf area, soil Olsen P, pH, and phosphorus and nitrogen of shoots, nodules and seeds were measured. The results have shown that the RILs responded positively to P application levels. The best values were observed in RILs 75, 83 and 34.Vegetative growth parameters were significantly enhanced by increasing levels of phosphorus. The highest level of P i.e.90 kg ha-1 P2O5 gave the optimal values of growth parameters for all common bean RILs while control plants obtained the lowest values. An increase of Olsen P and a decrease of soil pH were also observed with increases in phosphorus. These results led to the conclusions that phosphorus applied to Nubaria soil i) improved the soil fertility, ii) enhanced the ability of root nodules of common bean RILs to fix atmospheric nitrogen and iii) increased the release of H+ by roots, thus decreasing soil pH and reducing the immobilization of phosphorus in the soil solution and transforming it into available form for the plant.