Soil acidity on nitrogen fixation in common beans

Abstract

This experiment aimed to evaluate common beans (Phaseolus vulgaris L.) response to different soil pH levels in the presence and absence of inoculation. Three grams of peat based inoculant with 107 viable cells g^-1 of Rhizobium tropici II B strain CIAT 899 were mixed with 5 kg soil samples in plastic bags and incubated for 30 days. Part of the inoculated samples was humidified, another part received CaCO₃ and MgO to increase pH to 5.0 and 5.5 and a third part received acetic acid to decrease soil pH to 4.0. Before sowing, seeds were disinfected and (a) part of them was inoculated with 1 mL per seed of liquid culture of R. tropici II B CIAT 899 107 UFC mL-1,while the remainder was not inoculated again. Chemical fertility characteristics were determined at each experimental unit before sowing as well as shoot, root system and nodules dry matters, total N, nodule number and size at 21 days after sowing. Linear correlation analyses were done for soil plant and nodulation characteristics at each harvest time. Low soil pH affects more bean plant in the initial growth stages, while the soil-inoculated rhizobium strain survives, nodule beans and shows effective symbiosis, as indicated by plant N contents.