| In this paper, methods of most probable number (MPN) and cotton buried in soil were used to study the effects of two rotation systems on the quantity of cellulose-decomposing bacteria and the intensity of cellulose-decomposition in black loessial soil on the Loess Plateau, including the wheat-alfalfa rotation (rotation conducted in the order of alfalfa, alfalfa, alfalfa, alfalfa, potato, wheat, wheat, and wheat) and the wheat-sainfoin rotation (rotation implemented in the order of sainfoin, wheat, and wheat with sainfoin). The results showed that rotation systems and cropping years of rotated plants affected the quantity of cellulose-decomposing bacteria more significantly than the intensity of cellulose-decomposition. The quantity of cellulose-decomposing bacteria showed significant variations with different treatments, reaching the highest values during the first years in alfalfa through the wheat-alfalfa rotation and during the second years in wheat through the wheat-sainfoin rotation, and reaching the minimum values in potato through the wheat-alfalfa rotation and during the first years in wheat through wheat-sainfoin rotation. Though the differences in cellulose-decomposition intensity of each crop in the same rotation systems were not significant, crop rotation could obviously improve the intensity of cellulose-decomposition. The quantity and intensity both generally showed a decreasing trend with planting time forwarding. The effect of the wheat-sainfoin rotation on the quantity of cellulose-decomposing bacteria was less apparent than that of the wheat-alfalfa rotation, whereas played a more import role in improving the intensity of cellulose-decomposition. |