Banca de QUALIFICAÇÃO: CAROLINA ALMADA GOMES DE OLIVEIRA

FBN on biomass productivity and nitrogen accumulation of elephant grass grown in low fertility soil

Biomass; Bioenergy; 15N; Natural Abundance of 15N; BNF

Elephant grass is a crop that has a high potential to accumulate dry matter and has the ability to benefit from FBN. This work proposed to evaluate the effect of FBN on biomass productivity and nitrogen accumulation by different genotypes of elephant grass. The experiment was carried out with ten grass genotypes, grown in a 120 m2 concrete tank, filled with typical dystrophic red Argisol soil marked with 15N, located in the experimental area of Embrapa Agrobiologia, Seropédica-RJ. The experimental design was in randomized blocks with four replications and evaluated during 6 cultivation cycles, lasting 6 months each. In each cut, the productivity of fresh and dry mass of the aerial part (straw, leaves and stems), the accumulation of N in the plant and the contribution of FBN were evaluated using the 15N natural abundance technique. There was a treatment effect for the parameters of fresh mass, dry mass and contribution of FBN in almost all cycles evaluated. The average annual FBN rate was 38%. The annual average of fresh mass, dry mass, total N and N derived from FBN for the genotypes was approximately 15 Mg ha-¹, 8 Mg ha-¹, 34.3 kg ha-¹, 11.8 kg NdFBN, respectively. The genotypes P13G13, P21G15, P27G19 and BRS Capiaçu showed the best responses to FBN in the experiments and can be recommended for cultivation under conditions similar to those of the study. The biomass accumulation of elephant grass is positive even when grown in low fertility soil and without the use of synthetic nitrogen fertilizer.