秸秆不同还田方式下线虫添加对土壤活性碳氮的影响

土壤活性碳氮(C、N)是农田生态系统养分循环中最活跃的部分,其含量受到秸秆还田方式的影响,同时受到土壤微型生物对土壤养分循环影响的调控。然而,秸秆还田和微型生物双重作用下土壤活性C、N会呈现怎样的变化,尚需要深入探究。本研究以5 kGy低剂量γ辐射后微生物群落基本完整的土壤为供试土壤,接种从新鲜土壤中提取的整个线虫群落,在培养期154天内的不同阶段测定土壤活性C、N的含量。试验设置4个处理:(1)秸秆表施(无线虫添加),(2)秸秆表施+线虫,(3)秸秆混施(无线虫添加),(4)秸秆混施+线虫。结果表明:在较短时间内获得了接种率达到定殖标准(70%)、营养类群趋于稳定的土壤线虫群落。土壤活性C、N含量随培养时间的增加呈阶梯式增加或减少的变化趋势,但与无线虫添加的处理相比,线虫添加处理的土壤CO_(2)释放速率、微生物生物量碳(MBC)、微生物生物量氮(MBN)含量较高,土壤可溶性有机碳(DOC)、可溶性有机氮(DON)、矿质氮(MN)和铵态氮(NH_(4)^(+))含量较低,而硝态氮(NO_(3)^(−))含量在培养7~54 d低于无线虫添加的处理,在培养91~154 d高于无线虫添加的处理。从整个培养期间来看,秸秆混施方式下线虫添加对MBC含量的促进效应显著低于秸秆表施,对NO_(3)^(−)的促进效应显著高于秸秆表施。本研究结果有利于厘清土壤线虫在秸秆还田方式下对土壤活性C、N周转的调控作用,为土壤农田生态系统C、N循环研究提供科学依据。

Effect of Incorporation of Wheat Straw and Urea into Soil on Biomass Nitrogen and Nitrogen-Supplying Characteristics of Paddy Soil

Pot experiments were carried out to study the effect of incorporation of wheat straw and/ or urea into soil on biomass nitrogen and mineral nitrogen and its relation to the growth and yield of rice. The combined application of wheat straw and urea increased much more biomass nitrogen in soil than the application of wheat straw or urea alone and consequently increased the immobilization of urea nitrogen added and reduced the loss of urea nitrogen. An adequate nitrogen-supplying process to rice plant could be obtained if C / N ratio of the material added was about 20. The three yield components of rice were affected significantly by the status of nitrogen supplying. More than 30mg N / kg soil of mineral nitrogen at effective tillering stage, panicle initiation stage and filling stage should be maintained in order to get high rice yield, though the criteria varied with the different experimental conditions.