Interference of calcium and nitrogen in symbiotic nitrogen fixation of two bean varieties (Phaseolus vulgaris L.)

Abstract

A greenhouse experiment was carried out to study the interference of calcium and nitrogen in symbiotic nitrogen fixation of beans. The experiment had a factorial design including four calcium levels, four nitrogen levels and two varieties, namely Venezuela and Rico 23. The variety Venezuela showed more abundant nodulation, which was less affected by environmental effects not controlled in this experiment. Both varieties increased nodule weight at the 10 ppm N-level but this increase varied with the variety at different calcium levels. N at 40 ppm reduced nodulation in all treatments except the variety Rico 23 at the two lowest calcium levels. Neither of the varieties fixed nitrogen equivalent to 40 ppm of N applied as fertilizer, the variety Venezuela with 200 ppm of gypsum reaching the highest amount of N fixed (95% of the maximal total N reached by this variety with 40 ppm N). The nitrogen fixation of the variety Rico 23 reached only 50% of the best treatment with 40 ppm of N. It was concluded that physiological differences between bean varieties related to calcium and nitrogen nutrition can be responsible for plant determined deficiencies in nodulation.