Agronomic efficiency of rhizobia strains in cowpea cultivated in the Pre‑Amazon region, in Maranhão state

Abstract

The  objective  of  this  work  was  to  evaluate  the  agronomic  efficiency  of rhizobia strains for inoculation, in field conditions, of the cowpea BRS Guariba cultivar. Experiments were carried out in two areas in Santa Luzia do Paruá, Maranhão state, Brazil, in the Pre‑Amazon region, in 2009. The BR  3299, BR 3262, INPA 03‑11B Bradyrhizobium strains, an absolute control, and a nitrogen treatment (80 kg ha^-1 N) were tested. At 30 and 50 days after emergence (DAE) of plants assesments were made. At 65 DAE, grain yield was evaluated. The number and dry weight of nodules, shoot dry mass, relative efficiency, and N accumulation in shoots were evaluated. All strains provided higher values for number and dry weight of nodules, and higher productivity in comparsion to the absolute control, without inoculation and urea, in the two areas. Regarding shoot dry matter, relative efficiency, and N accumulation in shoots, BR 3299 differed significantly from the absolute control, at 30 DAE, in one of the farms. Cowpea yield responds positively to inoculation with strains, especially strain BR 3299.