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【目的】利用东北黑土13年保护性耕作定位试验,研究耕作措施(免耕和秋翻处理)对土壤微生物的影响,从土壤微生物角度分析免耕是否有利于土壤有机碳(SOC)的固定,为合理评价农田黑土碳“源”与“汇”功能提供科学依据。【方法】以连作玉米为研究对象,采用单因素随机区组设计,耕作处理包括免耕和秋翻。免耕除播种外不扰动土壤,秸秆覆盖地表。秋翻处理的田间管理包括人工除草、中耕起垄和秋翻,秋翻时将秸秆翻于地表之下。土壤微生物呼吸速率通过PVC环在野外采用动态气室法(Li-Cor8100)直接测定(去除植物根系),定期监测土壤微生物呼吸速率的季节变化,并在土壤微生物呼吸速率最高的季节取样分析不同处理土壤微生物量碳和数量特征。【结果】生长季节内免耕和秋翻处理下土壤微生物呼吸速率分别为0.42—3.35和0.48—3.24μmol CO2·m-2·s-1,两处理平均值差异不显著(8.8%),但土壤累积CO2-C释放量免耕比秋翻高10.0%(2012)和4.3%(2013)(P<0.05)。免耕显著地增加0—5 cm表层土壤细菌、真菌和放线菌的数量,分别比秋翻高125.7%、112.4%和53.3%;还显著地增加了其他土层的真菌数量,分别为105.3%(5—10 cm),159.4%(10—20 cm)和114.7%(20—30 cm)。耕作处理影响土壤温度,主要体现在春季,秋翻(0—5 cm,5—10 cm)春季(6月)土壤温度比免耕分别高2.8%和5.8%。土壤微生物呼吸速率表现出显著的季节变化规律,与土壤温度具有相似的动态变化,夏季(7、8月份)最高,秋季较低。尽管耕作处理没有明显地影响土壤微生物呼吸速率的季节动态格局,但秋翻的土壤微生物呼吸最高值比免耕晚半个月。土壤微生物呼吸速率随土壤温度(5 cm和10 cm)呈指数型增长,10 cm处的回归模型明显好于5 cm。耕作处理只改变了5 cm的Q10值,免耕比秋翻高10.8%。土壤微生物呼吸速率与土壤温度、水分混合回归模型能更好地反应其变化规律,解释土壤微生物呼吸速率变异的65%(秋翻)和81%(免耕)。【结论】免耕增加了表层(0—5 cm)的SOC含量,从而使得该土层的土壤微生物量碳和活性增加,但是由于免耕处理增加0—30 cm土层SOC含量的加权平均值,因此相对于传统的耕作措施(秋翻),免耕有利于SOC含量的增加。
【Objective】 The aim of this study was to evaluate the effects of tillage (no-tillage and autumn tillage) on soil microbes by using 13-year conservation tillage positioning experiments on black soil in northeastern China. Whether tillage was beneficial to the fixation of soil organic carbon (SOC) In order to provide a scientific basis for evaluating the function of carbon “source” and “sink” of farmland black soil reasonably. 【Method】 Continuous cropping maize was used as research object. Single-factor randomized block design was used. Tillage treatments included no-tillage and autumn turning. No tillage except seeding does not disturb the soil, straw covering the surface. Field management of the autumn fall treatment includes artificial weeding, cultivating ridge and fall turn, fall turn the straw turned under the surface. The respiration rate of soil microorganisms was measured directly in the field (removal of plant roots) by the dynamic gas-chamber method (Li-Cor8100) in the field through PVC ring. The seasonal changes of respiration rate of soil microorganisms were monitored regularly. Samples were analyzed during different seasons of soil microbial respiration Soil microbial biomass carbon and quantity characteristics 【Result】 The results showed that the respiration rates of soil microorganisms under no-tillage and turning-over treatments during the growing season were 0.42-3.35 and 0.48-3.24μmol CO2 · m-2 · s-1, respectively, with no significant difference (8.8%) between the two treatments Soil CO2-C release increased by 10.0% (2012) and 4.3% (2013) in no-till tillage than in autumn (P <0.05). No-tillage significantly increased the number of topsoil bacteria, fungi and actinomycetes in 0-5 cm soil layer, which were respectively 125.7%, 112.4% and 53.3% higher than that in autumn, and also significantly increased the number of fungi in other soil layers, which were 105.3 % (5-10 cm), 159.4% (10-20 cm) and 114.7% (20-30 cm). Tillage treatments affected soil temperature, mainly in spring, autumn (0-5 cm, 5-10 cm) in spring (June) soil temperature was 2.8% and 5.8% higher than no-tillage. The respiration rate of soil microorganisms showed a significant seasonal variation with similar dynamic changes to soil temperature, with the highest in summer (July and August) and the lowest in autumn. Although the tillage treatments did not significantly affect the seasonal dynamic pattern of soil microbial respiration rate, the highest soil microbial respiration of autumn mulching was half a month later than no-till. The respiration rate of soil microorganisms increased exponentially with soil temperature (5 cm and 10 cm), and the regression model at 10 cm was significantly better than 5 cm. Tillage treatment only changed the Q10 value of 5 cm, no-tillage rose 10.8% over autumn. Soil microbial respiration rate and soil temperature and water mixed regression model can better reflect the variation of soil microbial respiration rate explained 65% (autumn turning) and 81% (no-tillage). 【Conclusion】 No-tillage increased the SOC content of the surface layer (0-5 cm), resulting in an increase of soil microbial biomass carbon and soil activity. However, no-tillage treatments increased the SOC values of 0-30 cm soil layers , No-tillage contributes to the increase of SOC content relative to the traditional tillage (autumn turning).