中文摘要：

通过田间试验研究不同灌溉水矿化度和施氮量对土壤微生物数量、土壤呼吸及土壤微生物群落功能多样性的影响。试验设置3种灌溉水矿化度（电导率,EC1∶5）分别为0.35、4.61和8.04 d S·m-1（分别代表淡水、微咸水和咸水）;同时,设置4个施氮水平：0、240、360和480 kg N·hm-2。结果表明：细菌数量随灌溉水矿化度的增加呈先增加后降低的趋势,施用氮肥可增加细菌数量,但当氮肥用量超过240 kg·hm-2后,细菌数量显著降低;真菌和放线菌数量随灌溉水矿化度的增加而增加,与不施氮相比,施用氮肥显著降低放线菌数量;淡水处理细菌/真菌显著大于微咸水和咸水处理,分别较微咸水和咸水处理高29%和86%,细菌/真菌在240 kg N·hm-2处理下最高;土壤呼吸随灌溉水矿化度的增加而显著降低,淡水处理分别较微咸水和咸水处理高12%和33%,土壤呼吸随施氮量的增加而增加,360和480 kg N·hm-2处理分别较不施氮处理增加48%和51%;AWCD值随灌溉水矿化度的增加而降低,淡水处理AWCD值分别较微咸水和咸水处理高3%和13%;灌溉水矿化度对丰富度指数、Shannon指数和Shannon均匀度指数无显著影响,但对Simpson指数影响显著,咸水处理Simpson指数最高,240 kg N·hm-2施氮处理土壤微生物群落多样性指数最高。因此,咸水灌溉显著影响土壤微生物数量和群落功能多样性,合理施用氮肥有助于保持土壤微生物活性和多样性。

英文摘要：

The effect of irrigation water salinity and N application rate on soil microbial popula- tions, soil respiration and soil microbial community functional diversity were investigated in a field experiment. The experiment used a 3×4 factorial design with three irrigation water saliniza- tion levels （fresh water, brackish water, or saline water） and four N application rates （0, 240, 360 or 480 kg N ·hm-2）. The results showed that bacterial populations increased first and then decreased with increasing the irrigation water salinity, bacterial populations increased with the N application rate, but significantly reduced when excessive N was applied （〉240 kg N ~ hm-2）. Fungi and actinomyces populations were significantly increased with the increase of irrigation wa- ter salinity, actinomyees populations decreased with the increase of N application rate. The bac- teria-to-fungi ratio was 29% lower in the brackish water treatment and 86% lower in the saline water treatment than in the fresh water treatment. The highest bacteria-to-fungi ratio was observed in the 240 kg·hm-2 treatment. Soil respiration decreased significantly with the increase of irriga- tion water salinity. Soil respiration in the fresh water treatment was 12% and 33% higher than that in the brackish and saline water treatments, respectively. Soil respiration increased with the increase of N application rate, and 360 and 480 kg N · hm-2 treatments were 48% and 51% higher than that without N application. AWCD was decreased with increasing the irrigation water salinity, and the AWCD was 3% lower in the brackish water treatment and 13% lower in the sa- line water treatment than in the fresh water treatment. There were no significant differences in richness, Shannon＇ s index and evenness among the fresh water, brackish water and saline water treatments. Simpson index was the highest in the saline water treatment, and the highest soil microbial community diversity index was observed in the 240 kg N · hm-2treatment. Therefore, soil microorga