Liquid Inoculation with Rhizobia in the Planting Furrow of Common Bean under No-Till Is Feasible under Different Soil and Climatic Conditions

Common bean (Phaseolus vulgaris L.) producers that have adopted a high level of technology have shown interest in the use of liquid inoculant in the planting furrow, especially because of the practicality of this operation in large-scale planting operations. However, consistent information on this practice is lacking for common bean, which requires studies to assist the producer in the choice of the inoculation method to be adopted and in determination of the application rates adequate for good performance of biological N-2 fixation. To that end, two field experiments were conducted under the no-till system under different soil and climatic conditions, both of them in irrigated areas. A randomized block experimental design was used, with four replications and seven treatments (three rates of liquid inoculation in the planting furrow; peat-based or liquid inoculation on the seed; and two control treatments without inoculation, without and with N-urea). The cultivar used was BRSMG Madreperola and the rhizobial strain was CIAT 899 (+/- 10(9) cells of Rhizobium tropici per milliliter or gram). Inoculation on the seed was performed shortly before sowing. Inoculation in the planting furrow at the rate of 3.5 L ha(-1) not only leads to higher yields than inoculations on the seed but also ensures bean seed yields equivalent to those of the treatment with mineral N. Therefore, due to operational practicality, inoculation in the planting furrow is the most advantageous of the inoculations tested, regardless of the soil and climatic conditions in this study.