New strains of bradyrhizobium enrich plant biomass nitrogen content inlegume species for use as green manure

Abstract

The use of leguminous species such as Crotalaria spectablilis and Stizolobium aterrimum in symbiosis with rhizobia efficient in green manure is promising, since it can maximize the production of nitrogen-enriched phytomass through biological nitrogen fixation (FBN). Previous studies point to the symbiotic efficiency of rhizobia that could expand the list of strains approved as inoculants for C. spectablilis and S. aterrimum, requiring field evaluations to confirm the good results verified in the greenhouse. Therefore, the objectives of this study were: i) to evaluate the symbiotic and agronomic efficiencies of new strains of Bradyrhizobium in C. spectablilis and S. aterrimum, in pots with soil and in the field, in order to corroborate their indication as inoculants for these species; ii) determine, through an FBN march, the contribution of new strains of Bradyrhizobium in the accumulation of N in the phytomass of C. spectabilis in four cutting seasons for use as green manure and, iii) verify the contribution of inoculated S. aterrimum as green manure for subsequent silage corn. The experiments were carried out in Lavras-MG, always in random blocks, with four replications, and for C. spectabilis in the field, a split plot scheme was also adopted. In pots, the efficiency of treatments, for both green manures, was evaluated at 60 days after sowing (DAS), and also at 140 and 100 DAS for C. spectabilis and S. aterrimum, respectively. In pots, the efficiency of treatments, for both green manures, was evaluated at 60 days after sowing (DAS), and also at 140 and 100 DAS for C. spectabilis and S. aterrimum, respectively. The latter was also evaluated at 170 DAS (flowering) in the field. The contribution of inoculated S. aterrimum and starter fertilizer was also evaluated in the agronomic efficiency of subsequent silage corn in the field Strains UFLA05-03, UFLA05-09 and UFLA05-14 are efficient in C. spectabilis. The strain UFLA05-03 has biotechnological potential as an inoculant for the species; inoculation in C. spectabilis increases the production of N-enriched phytomass and can benefit subsequent cultivation. The new strains inoculated in S. aterrimum increase the productivity of N-enriched phytomass for green manure; S. aterrimum straws with starter fertilizer and inoculated with strains UFLA05-19, UFLA05-20, BR2811 and INPA104A increase the productivity of silage corn.