Direct and residual effect of different levels of nitrogen fertilisation on growth and yield of Brachiaria ruziziensis at different phenological stage. [French]Original Title Effet direct et residuel de differents niveaux de fertilisation azotee sur la croissance et le rendement de Brachiaria ruziziensis a differents stades phenologiques.

摘要

The direct and residual effect of different levels of nitrogen fertilization on growth and biomass production of Brachiaria ruziziensis at different phenological stages was assessed at the Research and Experimental Farm of the University of Dschang in 2008 and 2009. 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 (4x2 m) in four replicates, (i.e. a total of 72 plots) was used. No fertilizer has been applied in the second year. At each phenological stage during the first and second year, 120 plants were harvested by treatment for measurements of heights and diameters. The evaluation of the biomass of stems, leaves and whole plant was made on each plot based on the level of nitrogen fertilization and phenological stage at the first and second year. The results obtained showed that nitrogen fertilization and growth stage influenced significantly (P<0.05) height and diameter of B. ruziziensis during the first and second year of mowning. Regardless of growth stage, height and diameter, higher plants have been obtained with fertilization at the dose 200 kg N/ha while in the second year they were obtained with the dose 250 kg N/ha. Irrespective of fertilization and year of mowning, the biomass of stems and whole plant of B. ruziziensis significantly (p<0.05) increased with phenological stage. The highest biomass of leaves was obtained at flowering (8.42+or-1.23 t DM/ha and 11.34+or-0.32 t DM/ha respectively in the first and second year). The results obtained show that under the conditions of the trial the direct effect of fertilization at the dose of 200 kg N/ha and the residual effect of fertilization at the dose of 250 kg N/ha allow to have the highest growth of B. ruziziensis in terms of height, diameter and biomass.