长期施肥对植烟土壤微生物的影响

【目的】微生物是土壤的重要组成分，与土壤养分转化供应密切相关。本研究利用12年肥料定位试验研究了云南植烟土壤可培养微生物数量、微生物量碳氮、标记性磷脂脂肪酸（PLFAs）、微生物种群特征及有益微生物的变化。【方法】试验设置不施肥（CK）、单施化肥（CF）和化肥配施有机肥（CFM）处理，在烟株旺长期，采集020 cm耕作层土壤，测定了微生物量碳、氮含量，微生物标记磷脂脂肪酸（PLFAs）含量和可培养微生物数量；鉴定自生固氮菌、磷细菌和钾细菌的数量；根据PLFAs计算了微生物种群特征值。【结果】有机无机肥配施处理的土壤中，可培养细菌比不施肥土壤增加了6.14倍、 真菌增加了2.30倍、 放线菌增加了1.56倍，增幅显著高于化肥处理；施肥显著提高土壤微生物量碳、氮量。化肥和有机无机肥配合处理土壤的微生物量碳分别比CK增加了71.8%和246%；不同施肥处理土壤微生物量碳/氮比值显著不同，分别为14.8（CK）、13.3（CF）和11.2（CFM）。微生物标记性PLFAs含量以化肥有机肥配合处理最高，化肥处理次之，CK最低。化肥、化肥配施有机肥处理土壤细菌PLFAs比对照分别增加了25.41%和87.66%，真菌PLFAs分别增加了15.59%和39.24%，化肥处理代表放线菌的PLFAs降低了24.63%，化肥配施有机肥处理增加了83.86%，表明施肥尤其是化肥配施有机肥改善了土壤环境，促进了微生物的生长繁殖，并改变了土壤微生物种群结构；施肥处理土壤中微生物群落多样性指数上升，化肥处理还提高了微生物的优势度指数，说明施肥有益于增加微生物的种群数量， 化肥配施有机肥处理显著提高了无机磷细菌和钾细菌的数量，两者分别比对照增加了1.15倍和1.02倍，化肥处理则相反，自生固氮菌和无机磷细菌数量分别比CK降低了56.69%和41.30%；化肥配施有机肥处理土壤中的自生固氮菌、磷细菌和钾细菌共有20个属，CK土壤有19个属，化肥处理土壤仅16个属。 【结论】CFM促进微生物生长繁殖，增加种群多样性，有益于微生物固氮、溶磷、解钾，对于提高肥料利用率和保持土壤健康有重要意义。在烟叶栽培过程中，提倡化肥与有机肥配合施用很有必要。

Effects of long-term fertilization on soil microorganisms in tobacco fields

【Objectives】Microbes are important components of soils because they participate in nutrient turnover and supplies. A 12-year field experiment was used to investigate the effects of different fertilization on the soil cultural microorganisms, microbial biomass carbon(C) and nitrogen(N) contents, labeled phospholipid fatty acids (PFLAs) contents, microbial groups and beneficial microorganisms in tobacco cultivated fields. 【Methods】The soils from the three treatments were used: no fertilizer (control), single chemical fertilizer (CF) and combined chemical fertilizer and manure (CFM). Cultivated soils (0-20 cm) were sampled at the fast growing period of tobacco. Microbial biomass carbon and nitrogen, labeled phospholipid fatty acids of microbes were determined. The character values of microbial community including diversity, evenness and dominant indexes were calculated according to the corresponding content of PLFAs, the number of microorganisms were measured, the azotobacteria, phosphobacteria and potassium bacteria were indentified by microscope together with physiological and biochemical reactions. 【Results】The results showed more cultural microorganisms existed in the soil treated with CFM than with CF. Compared to CK, CFM increased the bacteria population by 6.14 times, fungi by 2.30 times and actinomycetes by 1.56 times, respectively, CF increased those obvious less than CFM. Fertilization also increased microbial biomass C and N contents. The microbial biomass C with CFM was increased by 2.46 times and 71.8% with CF than that with CK. The ratio of microbial biomass C to N changed with different treatments. CK showed the highest ratio (14.8), followed by CF (13.3) and the lowest with CFM (11.2). The total PFLAs in the soil with CFM is higher than soils with CF and CK. Compared with CK soil, the bacterial and the fungal PFLAs were increased by 25.41% and 15.59%, but the actinomycetal PFLAs was decreased by 24.63% in CF soil; all the bacterial, fungal and actinomycetal PFLAs were increased by 87.66%, 39.24% and 83.86% respectively in CFM soil. The phosphobacteria in the CFM soil was 1.15 times and potassium bacteria 1.02 times higher than those in CK soil, while the azotobacteria in CF soil was decreased by 56.69% and phosphobacteria by 41.30% than those in CK soil. There are totally 20 genera of azotobacteria, phosphobacteria and potassium bacteria in CFM soil, 19 genera in CK soil and 16 genera in CF soil. 【Conclusions】 Combined use of chemical and organic fertilizer in long-term promotes the microbial growth, reproduction and their biodiversity, resulting high fertilizer use efficiency and healthy soil with strong resistance to the potential decrease in microbial groups after a long-term application of chemical fertilizers. The chemical fertilizer plus manures in the tobacco cultivation should be advocated.