不同耕作方式对砂姜黑土孔隙结构特征的影响

砂姜黑土黏闭僵硬问题突出，耕作是改良其结构的重要措施之一。本文基于安徽龙亢农场砂姜黑土耕作试验基地，采集免耕（No-tillage, NT）、旋耕（Rotary tillage, RT）和深翻（Deep ploughing, DP）处理的原状土柱（高20 cm，直径10 cm），利用X射线CT扫描技术和ImageJ 软件等对土壤孔隙结构进行三维重建和可视化处理，定量分析了不同耕作方式对土壤的孔隙度、孔径大小分布、孔隙形态特征、网络特征以及土壤饱和导水率的影响。结果表明：（1）与免耕相比，旋耕和深翻下土壤的大孔隙度分别增加了192.7%和261.1%（P < 0.05）；与旋耕相比，深翻下土壤大孔隙度增加了23.4%；（2）相较于免耕，旋耕和深翻显著增加了土壤孔隙的水力半径、紧密度、分形维数和全局连通性（P < 0.05），显著降低了各向异性程度和欧拉数（P < 0.05），土壤饱和导水率得到显著提升，且深翻的改良效果总体优于旋耕；（3）相关分析表明土壤饱和导水率与除水力半径外的孔隙结构特征参数均存在显著相关（P < 0.05），其中与连通性最大孔隙度的相关性最高（r=0.833**，P < 0.01）。综上所述，深翻扩大了土壤孔隙的水力半径，改善了连通性，提升了复杂程度，从而构建了相对良好的土壤孔隙形态和网络结构，提高了导水能力，消减砂姜黑土结构性障碍效果显著。

Effect of Tillage Practices on Soil Pore Structure Characteristics in Shajiang Black Soil

【Objective】Shajiang black soil is one of the major soil types with low or medium productivity in China and is mainly distributed in the Huai River North Plain. As the soil is high in clay content and its parent material is dominated by montmorillonite, it suffers from swelling/shrinkage, low infiltration and strong strength. Suitable tillage is widely considered an effective measure to improve soil structure. However, how tillage practice impacts the pore structure of Shajiang black soil is not clear. Therefore, the objective of this study was to assess the effect of different tillage practices on soil pore structure characteristics in Shajiang black soil. 【Method】Intact soil columns (20 cm height, 10 cm diameter) were sampled from three tillage treatments including no-tillage (NT), rotary tillage (RT) and deep ploughing (DP) at Longkang Farm in Anhui Province, and then were scanned using X-ray computed tomography at a voxel resolution of 60 μm, and followed by saturated hydraulic conductivity (Ks) measurement. After reconstruction of CT images, characteristics of soil macropore (>60 μm) morphology and networks were quantified with Image analysis. 【Result】Compared to no-tillage, rotary tillage and deep ploughing increased soil macroporosity by 192.7% and 261.1% (P < 0.05), respectively. Rotary tillage and deep ploughing significantly increased the hydraulic radius, compactness, fractal dimension and global connectivity of soil macropores (P < 0.05), but decreased the degree of anisotropy and Euler number (P < 0.05). The Ks was significantly improved under rotary tillage and deep ploughing. Deep ploughing improved soil structure and Ks better than rotary tillage did. A significant correlation was observed between Ks and macropore structure characteristic parameters (P < 0.05), in which the connected largest macroporosity was the highest (r=0.833**, P < 0.01). 【Conclusion】Deep ploughing enhanced pore hydraulic radius, connectivity and complexity, built a good soil pore morphology and network structure and consequently improved hydraulic conductivity and reduced structural obstacles of Shajiang black soil.