利用计算机断层扫描技术研究土壤改良措施下土壤孔隙

为探明不同土壤结构改良措施（秸秆覆盖、免耕、有机肥、保水剂）对土壤孔隙特征及分布的影响，采用计算机断层（computed tomography，CT）扫描法定量分析了土壤孔隙的数目、孔隙度及孔隙在土壤剖面上的分布特征。结果表明：不同措施均提高了土壤总孔隙数、大孔隙数及0.13～1.0 mm孔隙数，且其孔隙度也相应提高。同时孔隙成圆率也得到了改善。各处理中以有机肥和免耕处理效果较佳，其次为保水剂和秸秆覆盖，对照最低。此外，不同措施显著提高了土壤的田间持水量和＞0.25 mm 水稳性团聚体含量，降低了土壤容重，且各处理中，仍以有机肥和免耕处理效果最佳，其田间持水量分别较对照提高了15.9%和16.4%，而土壤容重较对照降低了6.8%和8.8%。相关分析表明：田间持水量、容重和＞0.25 mm水稳性团聚体含量与土壤总孔隙度和大孔隙度呈显著或极显著正相关；而土壤容重对于总孔隙度和大孔隙度及孔隙成圆率呈显著负相关。

Using computed tomography scanning to study soil pores under different soil structure improvement measures

Abstract: Soil pore structure plays an important role in the ways of soil water movement in both topsoil and subsoil, and has a close relationship with soil surface runoff and permeability. Soil pore structure has evident spatial characteristics which includes soil porosity, pore number, pore radius, spore size distribution, circularity, morphological and quantitative characteristics, and the distribution of pore space, correlations between connectivity, and spatial pore distribution. In recent years, CT scanning has been introduced to study the characteristics of soil pores. CT image is applied to research the soil pore distribution, the density of soil spatial distribution and size, soil porosity, pore surface fractal dimension, the spatial distribution of soil moisture, and the unsaturated hydraulic conductivity of soil properties. Meanwhile, CT scanning has accurately revealed the number, size, and location of macro pores (>1 mm in diameter). No-tillage, straw mulching, application of organic fertilizer and superabsorbent polymers (SAP) can increase soil organic matter content, improve soil structure, increase soil fertility and soil porosity, and thus decrease soil bulk density and promote crop growth. However, further study will be needed to study the impact of different measures on the soil pore number, size, and distribution of soil pores in the soil profile. Therefore, in order to investigate the effect of different improvement measures for soil structure, such as straw mulching, no-tillage, application of organic fertilizer and super absorbent polymers, on the characteristics of soil pores and its distribution in different soil layer, CT scanning was used to quantitatively analyze soil pore numbers, soil porosity, and distribution of soil pores in different soil profiles. The results showed that the numbers of soil total pores, macro pores, and 0.13-1.0 mm pores were significantly increased in different soil improving treatments in contrast to CK treatment, and the porosity and circularity were improved. The optimal soil improvement measures occurred in treatments that applied organic fertilizer and no-tillage, and then were followed by the treatments of applying SAP and straw mulching, CK treatment was the lowest. In addition, soil field capacity and the amount of water stable aggregate of >0.25 mm were significantly improved in different soil structure improvement measures, however, soil bulk density was decreased in each treatment. The optimal soil improvement measures were also found in treatments that applied organic fertilizer and no-tillage, compared with treatment CK, soil water capacity was increased by 15.9% and 16.4% in treatment applications of organic fertilizer and no-tillage, respectively. In addition, corresponding soil bulk density was decreased by 6.8% and 8.8%, respectively. The correlation analysis among different soil pore indexes showed that these significantly or extremely significantly positive correlations were found between the field soil water capacity, and soil bulk density and the amount of water-stable aggregate of >0.25 mm and soil total porosity and macro porosity. However, soil bulk density and soil total porosity and macro porosity and pore cycle rate were submitted to a significantly negative correlation.