The effectiveness of the nitrogen supplying to bean plants as fertilizer and, or, as biological nitrogen fixation, and the dependence of these processes on molibdenum availability is still a not well solved problem. The objective of this study was to evaluate the effect of foliar application of Mo on nitrogenase and nitrate reductase activities and on productivity of beans cultivated on a Red Yellow Podzolic, in Coimbra, MG (Brazil). The treatments consisted of increasing rates of foliar application of Mo (0, 40, 80 and 120 g ha-1) 25 days after emergence. Fertilization was 20 kg ha-1 of N and 60 kg ha-1 of K2O applied during seeding. No N was applied afterwards. Foliar application of Mo increased and maintained nitrogenase and nitrate reductase activities during the whole plant growth cycle. Consequently, better crop productivities were obtained compared to the plants from the control. Maximum technical efficiency was obtained with 80 g ha-1 of Mo with productivity of 1,893 kg ha-1 of beans wich was 3.23 higher than that of the plants without Mo fertilization. Foliar application of Mo increased the number of pods per plant in 1.54 fold, the number of grains per pod in 0.23, and the weight of 100 grains in 0.15 compared to the control.
enzymes; micronutrient; Phaseolus vulgaris; nitrogen