有机种植对茶园土壤团聚体组成及稳定性的影响

Effects of Organic Farming on Composition and Stability of Tea Plantation Soil Aggregates

【目的】土壤团聚体是土壤最基本的结构单元,其组成和稳定性是衡量土壤养分含量和质量的重要指标,研究有机种植模式对土壤团聚体分布特征及稳定性的影响,可为优化茶园土壤管理和有机茶生态效应评估提供科学依据。【方法】选取闽东茶区2个茶叶种植基地的林地(FD)、常规茶园(CT)和有机茶园(OT)为研究对象,采用机械湿筛法测定土壤团聚体组成及团聚体稳定性指标,并分析其影响因素。【结果】>5 mm的大团聚体是林地和茶园土壤团聚体的主要组分,所占比例为27.84~78.16%。与林地土壤相比,常规茶园土壤大团聚体含量显著降低了32.73~56.51%,0.5~1 mm和0.25~5 mm大小团聚体含量显著增加,林地和有机茶园土壤各粒径之间差异不显著;水稳定性团聚体含量(R0.25)、平均重量直径(MWD)和几何平均直径(GMD)整体上表现为林地>有机茶园>常规茶园,分形维数(D)的变化趋势则相反,其中常规茶园MWD和GMD显著低于林地,林地和有机茶园之间差异不显著。相关分析发现,土壤团聚体组成及稳定性指标与土壤有机质、全氮、碱解氮、pH和土壤容重均显著相关。冗余分析(RDA)结果表明,土壤pH和土壤容重是影响土壤团聚体稳定性变化的关键环境因子。【结论】林地转变为茶园后,常规种植模式导致茶园土壤大团聚体含量显著降低,土壤团聚体MWD和GWD也显著下降;而有机管理模式则促进了土壤大团聚体的形成,增强了土壤团聚体稳定性,有利于实现茶园土壤可持续利用。

【Objective】Effects of tea cultivation practices on the makeup and stability of soil aggregates that affect the fertility and quality of the land were analyzed for the optimization of plantation management and ecology.【Method】At two tea growing areas in eastern Fujian,a forestland(FD)and a plantation operated under the conventional practice(CT)and one under organic farming(OT)were surveyed to analyze the differentiations on the soil structure.Using the wet screening method,soil aggregates at the locations were separated by the sizes of>5 mm,2~5 mm,1~2 mm,0.5~1 mm,0.25~0.5 mm,and<0.25 mm.Proportions of the varied particle sizes were calculated,and stability indicators monitored.【Result】The macro-aggregates(i.e.,>5 mm)accounted for 27.84~78.16%of the total and was dominant on the forestland as well as at the plantations(P<0.05).They were significantly lower in the soil of CT by 32.73~56.51%.And the CT lots had significantly more particles of 0.5~1 mm and 0.25~5 mm than did FD(P<0.05).But no significant differences in size distributions between the soils at FD and under OT.The moisture holding-stable particles(R0.25),mean weight diameter(WMD),and geometric mean diameter(GMD)of the soil aggregates at the different sites were generally ranked as FD>OT>CT,but opposite on fractal dimension(D).The MWD and GMD of CT soil aggregates were significantly lower than those of FD but not significantly different between those of OT and FD.The composition and stability indicators of the aggregates were closely related to the organic matter,total nitrogen,alkaline nitrogen,pH,and bulk density of the soil.And pH and bulk density were the major factors as indicated by a redundancy analysis(RDA).【Conclusion】After converting a forestland for conventional tea cultivation,the macro-aggregates,MWD,and GWD of the soil at the land were significantly reduced.However,if organic farming was implemented at the plantation,a significantly improved sustainable agriculture could be expected.