Symbiotic fixation and nitrogen nutrition of snap beam (Phaseolus vulgaris L) conducted in the open field

Snap bean nitrogen nutrition was studied on various cultivars in open field conditions. Aiguillon variety, more performant then Royalnel, answered well to inoculation and combined-N. Inoculation by strain CIAT 57 improved dry matter, yield, nodulation, N-composition and symbiotic fixation of plants. The fixation reached 38 to 49 units (U), respectively, in the case of Royalnel and Aiguillon. Nodulation was improved too by starter N (10 U at 10 DAE (days after emergence stage)) and by post-blooming N (30 U at 60 DAE stage). It was reversely inhibited by first- blooming N (30 U at 30 DAE stage). The optimal rate of combined-N was 60 U, fractionned as 10; 30 and 20 U, respectively, at 10; 60 and 80 DAE stages. As N-fertilizer rates increased, plants contained more nitrogen. Pods exported 40 to 4 7 % of total plant N, with 1/3 from biological fixation and 213 from combined-N. Late N-fertilization (80 DAE stage) was beneficiate to pod production.

Keywords: Phaseolus vulgaris L.- Nitrogen (Combined-N) - Symbiotic fixation - Open-field