不同水稻种植模式下淹水及排干期土壤性质和微生物的变化

Changes in soil properties and bacterial community during flooding and drainage periods under different rice planting modes

为揭示不同水稻种植模式、不同水分管理时期对稻田土壤性质和微生物的作用效应,利用长期定位监测试验比较分析单季稻不施肥、单季稻单施化肥、烟稻轮作3种种植模式和淹水期、排干期2种水分管理条件下稻田土壤理化性质和微生物群落结构的变化。结果表明:烟稻轮作模式稻田土壤有机质、全氮质量分数分别比单季稻模式提高了32.88%~34.79%和38.22%~44.39%。淹水期稻田土壤可溶性总氮以可溶性有机氮为主,占56.06%~62.54%;排干期以硝态氮为主,占62.34%~74.05%。烟稻轮作模式可显著提高淹水和排干条件下稻田土壤中可溶性有机氮和铵态氮质量分数,但对硝态氮质量分数的影响不明显。相较单季稻处理,烟稻轮作模式提高了稻田细菌Sobs、Shannon和Ace指数。好氧或兼性厌氧的酸杆菌属、黄色杆菌属均是3种水稻种植模式的优势菌属。3种种植模式淹水条件下稻田脱硫弧菌属、互营杆菌属等硫酸盐还原菌类存在显著差异,排干条件下硝化螺旋菌属也存在显著差异。淹水条件下烟稻轮作模式稻田土壤甲烷氧化菌相关的甲烷氧化单加氧酶基因α-亚基(pomA)的绝对丰度比单季稻处理降低了18.45%~18.54%。可见,水稻种植的淹水期和排干期的土壤可溶性氮组成和细菌群落结构存在显著差异;而烟稻轮作模式较单季稻模式可提高土壤肥力,改善微生物群落结构,增加硫酸盐还原菌类细菌丰度,降低产甲烷菌相关的甲基辅酶M还原酶基因丰度。

To study the effects of different rice planting modes and water management on soil properties and microorganisms in paddy fields,long-term monitoring experiments including single cropping rice with and without fertilization and tobacco rice rotation were used to analyze the changes in soil physical and chemical properties and microbial community structure during flooding and drainage periods of rice growth.The results showed that soil organic matter and total nitrogen levels were increased by 32.88%–34.79%and 38.22%–44.39%,respectively,under the tobacco rice rotation mode compared to those under the single cropping rice mode.During the flooding period,total dissolved nitrogen in the paddy soils mainly comprised dissolved organic nitrogen,accounting for 56.06%–62.54%.During the drainage period,nitrate nitrogen was the main form,accounting for 62.34%–74.05%.The levels of dissolved organic nitrogen and ammonium nitrogen in paddy soil under the tobacco rice rotation mode significantly increased during flooding and drainage conditions,but the change in nitrate nitrogen content was not significant.Compared to the single cropping rice treatment,the tobacco rice rotation mode improved the Sobs,Shannon,and Ace indices of bacteria in the paddy fields.Acidobacterium and Xanthobacter were both dominant in the three rice planting modes.There were significant differences in Thermodesulfovibrionia and Syntrophorhabdus during flooded conditions among the three rice planting modes,and there were also significant differences in Nitrospira under drainage conditions.The absolute abundance of pomA under the tobacco rice rotation mode decreased by 18.45%to 18.54%than that under the single cropping rice treatment.In conclusion,there were significant differences in soil dissolved nitrogen composition and bacterial community structure between the flooding and draining stages.Compared with the single cropping mode,the rotation mode of tobacco rice could improve soil fertility and microbial community structure,increase the abundance of sulfate-reducing bacteria,and reduce the abundance of mcrA genes.