RESPONSE OF COMMON BEAN CROP TO NITROGEN FERTILIZATION AND RHIZOBIUM INOCULATION

Adequate management of nitrogen fertilizer is one of the main difficulties on common bean ( Phaseolus vulgaris L.) crop. However, the biological N-2 fixation is an alternative source of N supply to this crop. This study had the purpose to evaluate the response of common bean to rhizobium inoculation and split application of N fertilizer in terms of plant nodulation and grain yield. Besides, this study aimed to evaluate the economic viability of using N fertilizer application and/or rhizobium inoculation on the plants. The experiment was carried out on a typic Haplustox in Dourados, Mato Grosso do Sul State. The experimental design was a completely randomized block with six replications. The seven treatments consisted of different levels of N fertilizer (0, 20, 40, 80, and 160 kg ha(-1) N as urea) applied to common bean, cultivar Perola, and control treatments with R. tropici inoculation with or without application of 20 kg ha(-1) N. In the economic analysis, the cost of urea, broadcast application, and cost of inoculant were taken into account. No other costs were considered since the treatments did not differ. Increases in grain yield, production cost, net and gross income, in relation to the control without inoculation and without nitrogen were obtained. The effect of inoculation of selected rhizobia on bean grain yield was similar to the application of 80 kg ha(-1) N. When supplied with 20 kg ha(-1) N at sowing, rhizobium inoculation increased grain yield and net income similarly to the application of 160 kg ha(-1) N and more than the treatment of 20 kg ha(-1) N without inoculant, which demonstrates the importance of the inoculant for an enhanced crop profitability.