ABSTRACT
Long-term cropping systems and crop rotation research is important in helping understand how these systems affect crop yields, yield stability, and soil physical and biological properties. Since the beneficial effects of forage legumes on soil properties are recognized, most long-term rotation studies include forage legumes. Quantity of crop residue returned to the soil was varied by changing the amount of forage legumes and green manure crops grown in the rotation. Higher yields where forage legumes were included in the sequence were partially attributed to improvement of physical conditions of the soil. The amount of crop residue returned to the soil was estimated based on considerations formulated by R. E. Lucas et al. Cropping systems that conserve soil C and N often increase crop yields because they promote the formation of stable aggregates and in turn increase capillary pore space. Since farming is a very competitive business, growers have adopted cropping systems which are economically more advantageous.
