覆草对果园土壤腐殖质组成和生物学特性的影响

在杏园和苹果园覆盖麦草，研究其对土壤腐殖质组成、微生物区系及土壤酶活性变化的影响。结果表明：覆草显著提高了土壤腐殖质的含量，褐腐酸（HA）含量及褐腐酸与黄腐酸比值（HA／FA）增大；重组腐殖质和松结态、紧结态腐殖质含量增高，尤其是松结态腐殖质不仅绝对含量提高，而且与重组腐殖质及紧结态腐殖质的相对含量也明显提高。覆草增加了土壤细菌、放线菌及氨化细菌和纤维分解菌的数量，降低了硝化细菌数量；同时提高了土壤多酚氧化酶、蔗糖酶、碱性磷酸酶、脲酶、纤维素酶活性，对过氧化氢酶活性影响不大。

Effects of Covering Straw in Orchard on Humus Composition and Biological Characteristics

The experiment was carried out to evaluate effects of covering wheat straw in apple orchard and apricot orchard on soil humus composition, microflora and soil enzyme activities. The results showed that after covering wheat straw, the contents of soil humus, humic acid(HA) and the rate of HA to fulvic acid(FA) were increased effectively; Contents of heavy fraction, loosely combined, tightly combined humus were also increased, and especially, the relative rate of loosely combined humus compared with heavy fraction humus and tightly combined humus was also increased obviously. The amounts of bacterium, antinomyces, ammonifying bacteria and cellulose-utilizing bacteria were increased, the nitrobacteria amount was decreased; the activities of polyhenol oxidase, sucrase, alkaline phosphatase, urease and cellulose were increased, but it didnt take much effect on the activity of catalase.