ABSTRACT
A. Soils and Cropping Sequence The major soil types encountered in the wheat belt of the Great Plains of North America, including Pacific Northwest and Canadian Prairies are:
• Mollisols (Borolls, Udolls, Ustolls, Ustorthents, Fluvents) which are spread across as large tracts in Central and Northern plains, occupying nearly 25% of the total area;
• Alfisols (Ustalfs, Ustolls) are predominant in Central and Southern plains, and cover nearly 18% of the plains zone;
• Aridisols (Argids), Entisols (Psamments, Aqults), and Ultisols are frequented in Western, Northeastern and Southern plains res pectively.
