Fractionnement de la fertilisation azotée minérale et organique: Effet sur la productivité du canola de printemps et sur les nitrates du sol

Abstract

The strategies of fertilization and nitrogen sources can have a direct impact on canola (Brassica napus) grain yield, nitrogen recovery and residual soil nitrogen. The objectives were to determine the effects of nitrogen sources and nitrogen split application on spring canola productivity and on residual soil nitrate. Four rates of mineral fertilizer (0, 37, 74 and 111 kg N ha -1) were compared with four rates of liquid dairy manure (0, 30, 60 and 90 m3 ha-1) and with four rates of liquid hog manure (0, 17, 34 and 50 m3 ha-1). The two higher rates were split at sowing (50%) and at the rosette stage (50%) of canola. Grain yields obtained with liquid manures and mineral fertilizer were comparable (3096 vs. 3062 kg ha-1). The split application of higher rates of mineral fertilizer and liquid hog manure had divergent effects according to the quantity of total nitrogen applied and climatic conditions. The apparent nitrogen recovery was higher with mineral fertilizer (37%) compared with liquid dairy manure (10%) and liquid hog manure (24 %). At the rosette stage, the soil nitrate (N-NO3) content increased with mineral fertilizer and liquid hog manure applications in the 0- to 30-cm soil layer, but decreased with split application. At harvest, only liquid hog manure increased soil residual N-NO3 in the 30- to 60-cm soil layer, suggesting the occurrence of leaching. However, the high mineralizable nitrogen potential of these soils reduced the effect of application rates and split application of nitrogen on canola productivity and residual soil nitrogen.