长期施肥水稻土氮素剖面分布及温度对土壤氮素矿化特性的影响

PROFILE DISTRIBUTION AND MINERALIZATION CHARACTERISTICS OF NITROGEN IN RELATION TO TEMPERATURE IN PADDY SOIL UNDER LONG-TERM FERTILIZATION

利用太湖地区26a的水稻土长期定位试验,研究了长期施肥对水稻土剖面氮素分布和C/N的影响,分析了10℃和30℃下不同施肥处理土壤氮素矿化过程的差异,拟合了30℃下土壤累积矿化量与有效积温的方程式。结果表明:(1)长期施肥使表层土壤氮素累积量明显增加,0～20cm土层,施有机肥处理的含氮量普遍高于施化肥处理。20～30cm土层,化肥氮+磷处理(CNP)、化肥氮+磷+钾处理(CNPK)、秸秆+氮处理(CRN)及不施肥对照CK的含氮量高于有机肥+氮+磷处理(MNP)、有机肥+氮+磷+钾处理(MNPK)、秸秆+有机肥+氮处理(MRN)和仅施有机肥处理(M0),而40～50cm土层含氮量差异较小;(2)施有机肥或秸秆还田使表层土C/N值有降低趋势。0～10cm表层土壤的C/N,CNPK>MNPK,CK>M0,而施秸秆处理MRN的C/N最低。20～50cm土层,施有机肥处理的C/N普遍高于化肥处理,施化肥土壤下层的有机质分解程度较高。(3)在30℃下,土壤矿化过程达到稳定状态需要时间较短,且累积矿化量较高。在10℃下,培养后期的矿化速率高于30℃下的速率,但累积矿化量较低,低温条件引起了土壤氮素矿化率的降低。土壤累积矿化量与有效积温的关系符合有效积温方程式(p<0·01),K值较接近反应矿化初期各处理的矿化潜力,n值的差异反应MRN、MNP以及CNPK、CNP处理在矿化后期有更高潜力。

Based on a 26-year-long fertilization experiment on a paddy field in the Taihu Lake Region,effects of long-term fertilization on profile distribution of soil nitrogen and C/N ratio,soil nitrogen mineralization characteristics under 10 ℃ and 30 ℃,and relationship between cumulative mineralization and effective accumulated temperature were studied. Results show： （1） Nitrogen accumulation significantly increased in the topsoil （0～20 cm）,where total nitrogen was higher in Treatments MNP （manure and fertilizer N,P）,MNPK （manure and fertilizer N,P,K）,MRN （Manure,rice straw and fertilizer N） and M0 （only manure application） than in Treatments CNP （chemical fertilizer N and P）,CNPK （Chemical fertilizer N,P and K） and CK （no fertilizer application）,however,in the 20～30 cm soil layer,it was just the contrary. And in the 40～50 cm soil layer,little difference was observed between the two groups; （2） Organic manure and straw applications may result in decrease in C/N ratio in the topsoil,where the ratio displayed an order of CNPK〉MNPK,CK〉M0,and was the lowest in MRN,while in the 20～50 cm soil layer,the ratio was were general higher in the organic manure treatments than in the chemical fertilizer treatments. And the subsoil in the chemical fertilizer treatments were higher soil organic matter decomposition degree; （3） Under 30℃ soil mineralization leveled off pretty quickly,but with high cumulative mineralization,while under 10℃,soil mineralization rate in the late incubation period was higher than under 30℃,but the cumulative mineralization was relatively lower. Obviously low temperature led to in decrease in soil mineralization rate. The relationship between cumulative mineralization and effective accumulated temperature well fit the effective accumulated temperature model （EATM） （p〈0.01）,its mineralization constant K reflected similar mineralization potentials of the various treatments at the initial stage of mineralization. Difference between treatments in mineralization constant n reflected higher mineralization potentials in Treatments MRN,MNP,CNPK,and CNP in the late stage.