Analysis of the relationship of oat grain chemical components with productivity can yield information that determines crop production strategies. The market values high protein grain, but production and other nutritional components may be affected in the effort to increase protein levels. The objective of this study was to determine how the dynamics of the components of oat grain chemical composition relate to productivity when adding nitrogen to the soil, in order to develop nutrient management strategies that can combine productivity with grain quality. The study was conducted from 2011 to 2016 in Augusto Pestana, Brazil, in a randomized block design with four replications in a 4x2 factorial design for nitrogen rates (0, 30, 60 and 120 kg.ha-1) and standard biotype oat cultivars used on a commercial scale (Barbarasul and Brisasul) in two succession systems soybean/oat and corn/oat, totaling 64 experimental units. The nitrogen doses were applied at the phenological stage of expanded fourth leaf using urea. The increase of nitrogen fertilization for topdressing promoted increase of the total protein of oat grains and reduction of the total fiber in both soybean/oat and corn/oat systems. Higher levels of grain protein due to nitrogen fertilization reduced grain production, regardless of the cropping system.

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