Utilisation de l'engrais azoté marqué au 15N par le maïs selon les modes d'application et les doses d'azote

Abstract

The main objective of this study was to compare the recovery of 15N-labelled fertilizer by different methods of N application and N rates. Field experiments were carried out for 3 yr at Saint-Hyacinthe (Saint-Damase, Du Contour, Sainte-Rosalie soils) and at Saint-Lambert, Lévis (Le Bras soil). Grain corn (cv. Pride K228, 2700 CHU) and silage corn (cv. Hyland 3251, 2300 CHU) were grown at Saint-Hyacinthe and Saint-Lambert, respectively. In 1988 and 1989, field trials were arranged in a randomized complete bloc design consisting of five treatments in three replications: control 0 N and four split application methods of N fertilizer. Labelled 15NH4 15NO3 fertilizer was applied either banded at planting as starter (D), broadcast and incorporated before planting (Vs) or sidedressing between rows at V6 to V8 stages of corn (Bp). In 1990 field trials, treatments consisted of four N rates (0, 60, 120 and 180 kg N ha−1) labelled with 15NH4 15NO3. The effect of N rates on yield and N uptake by corn was significant in all years. However, the effect of application methods was significant only on the soil Du Contour in 1989 where corn grain yield was highest when N fertilizer was split as starter and sidedress band. The CUR of N fertilizer applied broadcast before planting (42 to 48%) was generally lower than sidedressing band application (43 to 54%). N fertilizer recovery in the starter showed also high CUR values (45 to 60%). Consequently, it is recommended to split N fertilizers and apply in band to increase efficiency for grain corn. The CUR values decreased with N rates only in Le Bras soil in 1990. Residual N fertilizer increased from 27 to 103 kg N ha−1 for 60 and 180 kg N ha−1 rates, respectively. Consequently, the environmental impact of N fertilization may increased with high N rate. Key words: Grain corn, silage corn, 15N recovery, fertilizer N split application