作 者 ：谢驾阳,王朝辉*,李生秀
期 刊 ：生态学报 2010年 30卷 24期 页码：6781~6786
关键词：旱地；覆草；覆膜；轻质有机碳；轻质有机氮；微生物体碳；
Keywords:dryland, straw mulching, plastic mulching, light fraction organic nitrogen, light fraction organic carbon, microbial carbon,
摘 要 ：研究地表覆盖对土壤有机碳氮和生物活性的影响，对改进旱地作物栽培，提升土壤肥力和提高作物产量具有重要意义。采取5a田间定位试验的土壤进行室内培养试验，研究不同地表覆盖土壤轻质有机碳、轻质有机氮及微生物活性的变化。结果发现，经过61d培养之后，覆草、覆膜和常规土壤矿质态氮含量分别减少4.0，2.5，3.9 mg/kg，有机碳矿化累积量分别为125，100,101 mg/kg。覆草土壤微生物量碳含量及土壤代谢熵在培养过程中均高于覆膜。培养前后，覆草土壤的轻质有机碳氮均明显高于覆膜，覆膜和常规没有差异。培养结束后，覆草土壤轻质有机碳氮含量分别减少36%和47%，覆膜土壤分别减少26%和45%，常规土壤分别减少31%和44%。覆草土壤轻质有机碳氮含量的减少值明显高于覆膜和常规。覆草能增加土壤有机碳氮的易矿化组分，提高土壤有机质的生物有效性，覆膜则会降低土壤有机质的生物有效性。
Abstract:Soil organic matter is the basis of soil fertility and plays extremely important role in improvements of soil physical, chemical and biological properties, in maintenance of soil aeration, water retention and cultivation traits, in buffer of soil pH, and in supply of nutrients to plants as major nutrient source and pool. In soil, 95% nitrogen exists in organic form and the mineralization of organic matter constitutes the major source for soil to supply N to plants. Consequently, soil organic matter has been received great attention by agricultural scientists. It has been realized that cultivation methods affect organic matter accumulation and mineralization, and therefore its amount and characteristics. As an effective cultivation technique for crop production, soil surface mulching has been rapidly extended in dryland areas of northern China. The materials used for mulching include gravels, straw, crop stubble and plastic sheets or film, of which straw and plastic film are the most valuable ones for use in agricultural practice. However, how such mulching influences soil organic carbon composition, mineralization and its bioavailability remains unknown. For this reason, it is of great importance to study the soil micro-bioactivity and organic carbon and nitrogen under these mulching conditions. Such a study could provide information for improving soil fertility and thus for dryland crop production. The purpose of this study was to investigate the effects of straw and plastic-film mulching on soil micro-bioactivity, organic carbon and organic nitrogen. Soil used in the experiment was a type of Earth-cumuli-Orthic Anthrosols. The soil sample was taken from top layer (0-10 cm) at a site of a 5-year long term experiment field, located in the south edge of the Loess Plateau, Yangling, Shaanxi Province. It contained organic matter 13.79 g/kg，total N 1.07 g/kg, nitrate-N 5.4 mg/kg，ammonium-N 2.4 mg/kg，Olsen- P 15 mg/kg, and exchangeable K 182 mg/kg, with soil bulk density 1.35 g/cm3 and pH 8.25. Three treatments were arranged in the field trial: control (without mulching), plastic film mulching and straw mulching. The soil samples from the three treatments were used to determine the light fraction of organic carbon (LFOC) and the light fraction of organic nitrogen (LFON), and to measure the mineralization of carbon and nitrogen by laboratory incubation. Based on the determinations, microbial respiration intensity and metabolic entropy were calculated. Results showed that after 61 days incubation, contents of the mineral nitrogen initially present in soil were decreased by 40,2.5, 3.9 mg/kg for soil under straw mulching, plastic-film mulching and non-mulching, respectively. The cumulative C from the mineralization of soil organic carbon was 125,100,101 mg/kg for the three corresponding treatments, respectively. The microbial carbon and metabolic entropy of soil mulched by straw were higher than those of soil mulched by plastic-film. The contents of LFOC and LFON of the straw-mulched soil were significantly higher than those of the non-mulched soil (control). In addition, the contents of LFOC and LFON were reduced by 36% and 47% respectively for the straw-mulched soil, 26% and 45% for the plastic-film mulched soil, and 31% and 44% for the control. The absolute amounts of LFOC and LFON in soil were decreased by straw mulching and the decreases were significantly higher than those of the plastic-film mulching and the control. As a result, soil surface mulching with straw could increase the content of readily-mineralized parts of soil organic carbon and nitrogen, and improve the bio-availability of soil organic matter, while the plastic-film mulching could decrease their bio-availability.
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