Productivity and economics of inoculated common bean as affected by nitrogen application at different phenological phases

Abstract

Nitrogen fertilizers are widely used on the cultivation of common bean in Brazil, affecting the production cost and the environment. Biological nitrogen fixation (BNF) can reduce the negative impacts related to N supply. This work aimed to evaluate the agroeconomic response of the inoculated common to N-fertilizer topdressing at different phenological phases of the common bean. N-fertilizer in a total of 90 kg ha−1 was applied in the form of urea at 3 phases: planting (P), phenological phase V4 (V4), and phenological phase R5 (R5) of the common bean, in two field experiments. The used treatments were P0V40R50, P0V445R545, P0V490R50, P0V40R590, P30V430R530, P30V460R50, P30V40R560, P60V430R50, P60V40R530, and P90V40R50. All treatments were inoculated with peat inoculum containing the commercial strain SEMIA 4077 (Rhizobium tropici). The number of nodules (NN), nodule dry mass (NDM), leaf area index (LAI), root dry mass (RDM), shoot dry mass (SDM), grain yield (GY), production cost (PC), gross revenue (GR), net revenue (NR), and benefit-cost ratio (BCR) were determined. N-fertilizer splitting at any dose and phenological phase decreased NN and NDM. N-fertilizer treatments provided higher LAI and SDM compared with the inoculated treatment (P0V40R50). Inoculated treatment presented higher GY and lower PC, resulting in greater NR and BCR. Inoculation with Rhizobium tropici provided high nodulation to the common bean and increased its GY in 10.2% as compared with N-fertilization, which allowed a 15.8% and 7.8% higher NR and BCR, respectively, than the N-fertilized treatment.