The paper based on the research carried out during 2008-2010 in the long term trial placed in 1990 on the preluvosoil from Oradea. Three kind of crop rotation (wheat - monocrop; wheat - maize; wheat - maize - soybean) were studied in unirrigated and irrigated conditions. The smallest content of the protein from wheat grains were registered in the wheat monocrop both nonirrigated and irrigated variant. In the wheat-maize and wheat-maize-soybean crop rotation the values registered were significant statistically bigger than in wheat monocrop. Irrigation determined the decrease of the protein content.