Abstract
Dry bean is an important legume crop for a large portion of the world's population. Nitrogen (N) is one of the most yield-limiting nutrients in all dry bean–producing regions of the world. A greenhouse experiment was conducted to evaluate responses of 15 dry bean genotypes to N fertilization with and without rhizobial inoculation grown on a lowland soil locally known as Varzea. Nitrogen treatments were (i) 0 mg N kg−1 (control or N0), (ii) 0 mg N kg−1 + inoculation with rhizobial strains (N1), (iii) inoculation with rhizobial strains + 50 mg N kg−1 (N2), and (vi) 200 mg N kg−1 (N3). Shoot dry weight, grain yield, yield components, maximum root length, and root dry weight were significantly affected by N fertilization, rhizobial inoculation, and genotype treatments. The N × genotypes interactions were significant for shoot dry weight, grain yield, number of pods per plant, number of grain per pod, 100-grain weight, grain harvest index (GHI), and maximum root length and root dry weight. These significant interactions indicate that genotypes performance varied with varying N rates and inoculation treatments. Maximum grain yield was produced at 200 mg N kg−1 treatment. Inoculation with rhizobial strains improved grain yield but did not reach the level of 200 mg N kg−1 applied with chemical fertilizer. Based on grain yield efficiency index, genotypes were classified as efficient, moderately efficient, and inefficient in N-use efficiency. Overall, the most efficient genotypes were BRS Pontal, Diamante Negro, BRS Grafite, BRS Requinte, and BRS 9435 Cometa, and inefficient genotypes were BRSMG Talisma and Aporé.
Acknowledgment
Financial support for this research was provided by the Brazilian Scientific and Technological Research Council (CNPq) Grant No. 471032/2010-7.