Understanding the release and retention of nutrients from decomposing crop residue is critical to gain insight of nutrient cycling for sustained crop production. Using the mesh bag technique, we compared the mass loss and mineralization of N and P from straw and root residues of pea, canola and wheat in the 10 months following crop harvest. Wheat straw decomposed more slowly than either pea or canola mostly because of low N content, and released no measurable amount of N. By spring, pea straw had lost 25% of its N (7 kg N/ha) and canola straw 18% (2.5 kg N/ha). However, between spring and summer, these straw residues immobilized 1.5 to 2 kg N of soil N per ha. Wheat root lost more mass at the end of the study period than pea or canola root: Net mineralization of root residue N was 1 to 1.5 kg/ha. Residues of all test crops released P into the soil, however, the total amount from root and straw was less than 1 kg P/ha.