长期轮作对旱地黑垆土纤维素分解菌数量及分解强度的影响

采用最大或然数法(MPN法)和埋片法研究了黄土高原旱地粮草长周期(苜蓿→苜蓿→苜蓿→苜蓿→马铃薯→小麦→小麦→小麦)和粮草短周期(红豆草→小麦→小麦+红豆草)轮作制度及茬口年限对黑垆土纤维素分解菌数量和分解强度的影响。结果表明:轮作制度及茬口年限对黑垆土纤维素分解菌数量的影响程度大于分解强度。纤维素分解菌数量呈现显著性差异变化,分别在粮草长周期轮作中第1年苜蓿茬和粮草短周期轮作中第2年小麦茬达到最高值,在粮草长周期轮作中马铃薯茬和粮草短周期轮作中第1年小麦茬达到最低值;纤维素分解强度在同一轮作制度中各茬口差异不显著,但换茬可提高分解强度;随着苜蓿和小麦种植年限延长,纤维素分解菌数量和分解强度均大致呈现降低趋势。红豆草茬纤维素分解菌数量低于苜蓿茬,但粮草短周期轮作更有利于提高黑垆土纤维素分解强度。

Effects of long-term rotation on the quantity of cellulose-decomposing bacteria and the intensity of cellulose-decomposition in black loessial soil

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.