Growth and Biomass Production of Brachiaria Ruziziensis under different levels of Nitrogen Fertilization and Phenological Stage

The study of the growth and biomass production of Brachiaria ruziziensis under different levels of nitrogen fertilization and phenological stage was conducted at the Experimental farm of Research and Application of the University of Dschang in 2008. A factorial design comparing six doses of nitrogen (0, 50, 100, 150, 200 and 250 kg N/ha) and three phenological stages (bolting, flowering and after seed set) on plots of 8 m (4 x 2 m) in four replicates, a total of 72 experimental plots was used. At each phenological stage, 120 plants were harvested by treatment for the measurements of heights and diameters. The evaluation of the stems leaves and whole plant biomass was made on each plot depending on the level of nitrogen fertilization and stage of maturity. The results of this work have shown that nitrogen fertilization and stage of maturity have influenced significantly (P>0.05) the size, diameter and biomass of B. ruziziensis. Regardless of the fertilization, the size of plants increased significantly (p<0.05) with the phenological stage. The higher diameter (0.47 ± 0.06 mm) was obtained at flowering. The fertilization with 200 kg N / ha increase the size and diameter at all phenological stages. The stems, leaves and whole plant biomass has increased in general with the level of N fertilization to achieve maximum production with the level of fertilization of 200 kg N/ha at the bolting (6.11 ± 0.87, 7.13 ± 0.76 and 13.24 ± 0.70 t MS / ha respectively for leaves, stems and whole plant) and flowering (15.54 ± 1.96, 8.41 ± 1.23 and 23.96 ± 2.22 t MS / ha respectively for leaves, stems and whole plant). The highest biomass production of the leaf (7.13 ± 0.76 t MS / ha) was obtained at bolting, after seeding fort the stem (17.36 ± 0.84 t MS / ha) and at the flowering for whole plant (23.96 ± 2.22 t MS / ha). Regardless of the fertilization, the biomass of stems and the whole plant of B. ruziziensis increased significantly (p <0.05) with the phenological stage. The highest biomass of the leaves (7.05 ± 0.17 t MS / ha) was obtained at flowering. No significant interaction (p <0.05) was observed between the different levels of fertilization and phenological stages. The report stem/leaf increased with phenological stage and was not influenced significantly (p> 0.05) by nitrogen fertilization. This study shows that fertilization with 200 kg N/ha increase height, diameter and biomass of B. ruziziensis, and thus constitute the maximum level of fertilizer for this plant in these latitudes