BIOLOGICAL N2 FIXATION AND MINERAL N IN COMMON BEAN-MAIZE INTERCROPPING OR SOLE CROPPING IN SOUTHEASTERN BRAZIL

SUMMARY The aim of this work was to assess the effects of N levels and intercropping of two common bean (Phaseolus vulgaris) varieties (Carioca and Rio Tibagi) with maize (Zeamays) on accumulated N, grain yield and biomass of both crops, and nodulation of common bean inoculated or not with Rhizobium. Two field experiments were conducted simultaneously: common bean–maize intercropping and common bean in sole cropping. Intercropping increased common bean nodulation and biomass, mainly with Rhizobium, but mineral N was deleterious to nodulation. Inoculation also increased the Carioca cultivar yield most in sole cropping (+72 %), but N levels did not affect common bean yield in either cultivar. Although intercropping reduced maize grain yield by 17 %, the equivalent yield increased by 31 %, whilst Rhizobium increased it by 11 %. Despite the reduction of maize yield in intercropping, this system was shown to be more economically viable, in particular when common bean was inoculated with Rhizobium.