长期施肥对典型潮土钙、镁形态转化及其环境行为的影响

Effects of Long-term Fertilization on Calcium and Magnesium Morphological Transformation and Environmental Behavior in Typical Fluvo-aquic Soil

研究了长期(1989—2009年)不同施肥处理下潮土钙、镁累积特征及形态转化规律,探讨了两种典型盐基阳离子及其碳酸盐在农田土壤酸碱缓冲性能、有机质累积等环境过程中的作用。田间试验设置7个处理:有机肥(OM)、OM+无机化肥氮磷钾(NPK)、NPK、NP、PK、NK和不施肥(CK),OM+NPK处理为有机肥和无机化肥氮磷钾各施一半。气量法结合BCR形态分析结果显示,不同施肥条件下潮土耕层(0~20cm)钙、镁元素均出现持续累积过程,不同处理的累积量表现为:NK<OM<OM+NPK<NPK<NP<PK<CK,与土壤晶格态和碳酸盐结合态钙、镁含量变化规律一致,而与金属氧化物和有机复合态钙、镁含量变化规律相反。OM处理下潮土pH及钙、镁元素含量较低,对土壤碳酸盐影响较小。潮土中碳酸盐以碳酸钙为主,碳酸镁次之,部分碳酸根离子与有机质复合,其构成了土壤复杂的酸碱缓冲体系。钙离子与镁离子相比,易于与金属氧化物复合,与有机质的复合能力相对较弱,抑制土壤黏土矿物-金属氧化物-有机碳复合体的形成。

In this paper,the accumulation and morphological transformation of calcium(Ca)and magnesium(Mg)in typical fluvo-aquic soil under different long-term(1989–2009)fertilization treatments were studied and the roles of Ca2+,Mg2+and carbonate to soil buffering ability and organic matter accumulation were explored.7 fertilization treatments were designed in the field experiment:1)CK(non-fertilized control),2)OM(organic manure),3)OM+NPK(50%organic manure+50%mineral fertilizer),4)NPK,5)NP,6)PK and 7)NK.The results obtained by volume method and the modified BCR-sequential extraction method showed that the contents of Ca and Mg in topsoil(0-20 cm)accumulated continuously,and were in the order of NK<OM<OM+NKP<NPK<NP<PK<CK,which was in accordance with the contents of soil crystal lattice-bound Ca and Mg and carbonate-bound Ca and Mg,while contrary to the contents of metal oxide-bound and organo-bound Ca and Mg.pH,contents of Ca and Mg were lower under OM treatment,but OM treatment had little impact on the content of soil carbonate.CaCO3 is the main carbonates in soil,followed by MgCO3,they are bound to soil organic matter to form a complex acid-base buffering system in soil.Compared with Mg2+,Ca2+are easier to bind to the metallic oxide,whereas are weaker to be bound to soil organic matter,which may inhibit the formation of soil organo-mineral complexes.