不同母质发育的柑橘园土壤团聚体及有机碳分布特征

Distribution characteristics of soil aggregates and organic carbon in citrus orchards derived from different parent materials

作为土壤结构的基本单元和土壤肥力的组成部分,土壤团聚体对其物理、化学和生物学特性均具有重要影响。选取湖南省永兴县5种典型母质发育的柑橘园土壤,采用湿筛法研究不同成土母质的柑橘园土壤团聚体结构变化和有机碳分配规律。结果表明:(1)研究区不同母质发育土壤以>0.25 mm粒径团聚体为主,占85.94%~95.89%,其中板页岩风化物发育的黄泥土中大团聚体含量最高;(2)不同母质柑橘园土壤团聚体的水稳性大小为板页岩风化物(黄泥土)>第四纪红色粘土(红黄泥)>石灰岩风化物(灰红土)>砂砾岩风化物(红砂土)>河流沉积物(河砂泥);(3)不同母质柑橘园土壤团聚体有机碳含量、团聚体有机碳储量和团聚体对土壤有机碳的贡献率均随着团聚体粒径的减小而减少;(4)平均重量直径(MWD)、几何平均直径(GMD)、分形维数(D)和土壤可蚀性(K)与>2 mm团聚体间的相关系数最大,表明>2 mm团聚体含量是影响土壤团聚体稳定性的主要因子;(5)>2 mm团聚体有机碳贡献率与土壤团聚体MWD和GMD呈显著正相关,与土壤K值呈显著负相关,与土壤D值呈显著负相关。总体而言,目前南方柑橘果园施肥管理应注重增施有机肥,提高土壤结构的稳定性,从而降低水土流失的风险。

As a basic unit of soil structure and a component of soil fertility,soil aggregate has important influence on its physical,chemical and biological characteristics.Soil aggregate structure and organic carbon distribution of citrus orchard soils with different parent materials were studied by wet sieving method in Yongxing county,Hunan province.The results showed as follows:(1)Soil aggregates with particle size>0.25 mm were dominant in different parent materials,accounting for 85.94%~95.89%,and the content of soil aggregates developed in plate shale weathering was the highest.(2)The size of water stability of soil aggregates in citrus orchard with different parent materials were as follows:plate shale weathering(yellow soil)>quaternary red clay(red and yellow soil)>limestone weathering(gray red soil)>sandy conglomerate weathering(arenosols)>river sediments(river sand and mud).(3)Soil organic carbon content and storage in aggregates,and the contribution rate of aggregate to soil organic carbon were decreased with the decrease of aggregate particle size.(4)The correlation coefficients of mean weight diameter(MWD),geometric mean diameter(GMD),fractal dimension(D)and soil erodibility(K)were the largest with>2 mm aggregates,indicating that>2 mm aggregates were the main factors affecting the stability of soil aggregates.(5)The contribution rate of organic carbon of>2 mm soil aggregates was significantly positively correlated with soil aggregate MWD and GMD,significantly negatively correlated with soil K value,and negatively correlated with soil D value.In general,the fertilization management of citrus orchards in south China should focus on increasing organic fertilizer to improve the stability of soil structure and reduce the risk of soil erosion.