GROWTH AND YIELD OF COMMON BEAN AS AFFECTED BY SEED INOCULATION WITH RHIZOBIUM AND NITROGEN FERTILIZATION

Two field experiments were conducted during the rainy seasons of 2013 and 2014 to evaluate the effects of biological nitrogen fixation (BNF) and/or sowing N fertilization on the growth and yield of Phaseolus vulgaris L. In addition, leaf soluble protein content (LSPC) was measured at four growth stages in both seasons. Plants were subjected to the following treatments: only fertilized with 20 kg N ha−1 at sowing and with 40 kg N ha−1 at 25 days after emergence (DAE) (F); only inoculated with Rhizobium tropici strain SEMIA 4080 at sowing and fertilized with 40 kg N ha−1 at 25 DAE (I+N); and inoculated and fertilized with 20 kg N ha−1 at sowing and with 40 kg N ha−1 at 25 DAE (IF). An additional treatment was done only in the second season and plants were inoculated with no N fertilization at any phase (I−N). Crop growth rate and leaf area index were enhanced by IF and F treatments as compared to I+N treatment, however, net assimilation rate did not differ among the treatments. At the pollination and flowering stages for seasons, LSPC was significantly increased by IF treatment, which also caused the highest final yield compared with the remaining treatments in both seasons. Therefore, the fertilization with 20 kg N ha−1 at sowing together with inoculation and 40 kg N ha−1 at 25 DAE is recommended for obtaining high yield in bean cultivation with high technology. As the inoculation with Rhizobium at sowing and fertilization with 40 kg N ha−1 at 25 DAE (I+N) had the same crop yield as plants fertilized at sowing and at 25 DAE (F), it can be recommended for a low-cost technology cultivation employed by small farmers.