摘要:探明长期免耕措施对土壤孔隙特征、土壤结构及土壤水分参数等影响，可为阐明在小麦、玉米轮作过程中，长期进行免耕对土壤剖面物理特征的改善及其作用机理提供科学依据。采用CT扫描法定量分析了免耕和常规耕作0~100 cm土层土壤孔隙（80~1 000 μm、 > 1 000 μm、 > 80 μm）的数目、孔隙度及孔隙在土壤剖面上的分布特征，同时采用常规方法测定了土壤大团聚体、土壤容重、有效水含量及饱和导水率等。结果表明：长期免耕不仅提高了土壤 > 1 000 μm、80~1 000 μm、 > 80 μm孔隙数，且其孔隙度也相应提高，较常规耕作孔隙数分别提高55.3%、58.2%、57.9%，孔隙度分别提高97.4%、39.4%、72.6%。同时土壤孔隙形态也得到了改善，孔隙成圆率提高。对不同土层而言，免耕更利于提高0~25 cm土层80~1 000 μm和 > 80 μm孔隙数以及0~45 cm土层 > 1 000 μm孔隙数，且显著提高了0~20 cm和25~40 cm土层 > 1 000 μm、 > 80 μm及0~20 cm土层80~1 000 μm的土壤孔隙度。说明长期免耕对土壤剖面孔隙的分布产生一定影响。此外，免耕提高了0~25 cm土层土壤的有效水含量、0~55 cm土层饱和导水率和 > 0.25 mm水稳性团聚体含量，降低了土壤容重，其作用深度在55 cm以上土层。通过CT扫描测得的土壤孔隙参数与常规方法测定的土壤物理参数之间存在极好的相关性，说明可从微观土壤孔隙特征来表征宏观的土壤物理性质。总之，长期免耕有利于改善土壤结构和土壤孔隙状况，提高土壤的渗透能力及土壤水分的有效性，促进作物的生长。
关键词:免耕/
小麦玉米轮作/
CT扫描/
土壤结构/
土壤孔隙/
土壤团聚体/
水分参数
Abstract:Soil pore structure plays an important role in soil water movement in both topsoil and subsoil, and it is closely related to soil surface runoff and permeability. CT scanning has accurately revealed the number, size and location of macro-pores (> 1 mm in diameter). Long-term tillage can greatly influence the physical properties of soil profile, while non-tillage can improve soil structure, increase soil fertility and soil porosity, and thereby decrease soil bulk density and promote crop growth. Studies of non-tillage effects on soil pore have mostly been focused on the ploughed layer. Further study is needed to determine the impact of long-term non-tillage on soil pore volume, size and distribution along soil profile by using the CT scanning method and combining with soil structure, soil bulk density and soil moisture parameters investigation by using conventional method, especially for the deep soil (0-100 cm) layer. Thus in order to determine the effect of long-term no-tillage measure on pore characteristics, structure and water parameters of soil, CT scanning was used to quantitatively analyze soil pore volume (80-1 000 μm, > 1 000 μm and > 80 μm), porosity, and pore distribution of the 0-100 cm soil profile under long-term no-tillage and conventional tillage conditions in this study. A conventional method was adopted to determine macro-aggregate amount, bulk density, field water capacity, effective water content and saturated hydraulic conductivity. The results showed that no-tillage treatment increased numbers and porosities of soil pores > 1 000 μm, 80-1 000 μm and > 80 μm. The numbers increased respectively by 55.3%, 58.2% and 57.9%, while porosities increased by 97.4%, 39.4% and 72.6% of > 1 000 μm, 80-1 000 μm and > 80 μm pores under non-tillage treatment compared with the conventional tillage treatment. It was also found that pore shape and pore circularity improved under non-tillage treatment. For different soil layers, no-tillage treatment increased numbers of 80-1 000 μm pores and > 80 μm pores in the 0-25 cm and 80-100 cm soil layers, and number of > 1 000 μm soil pore in the 0-45 cm soil layer. Furthermore, there were significantly increases in porosities > 1 000 μm and > 80 μm soil pores in the 0-20 cm and 25-40 cm soil layers, and porosity of 80-1 000 μm soil pores in the 0-20 cm soil layer under non-tillage treatment compared with those under conventional tillage treatment. In addition, long-term no-tillage increased water content in the 0-25 cm soil layer, saturated hydraulic conductivity and content of water stable aggregates (> 0.25 mm) in the 0-55 cm soil layer. Then long-term no-tillage treatment reduced soil bulk density in the 0-55 cm soil layer compared with conventional tillage treatment. Correlation analysis showed that CT scanning well showed soil pore characteristics, which was related with soil physical parameters measured by conventional method. Also micro-cosmic soil pore characteristics could be used to characterize macroscopic physical properties of the soil. In summary, long-term non-tillage practice was beneficial for improvement of soil structure and pore, and increased soil water availability.
Key words:No-tillage/
Wheat-maize rotation/
CT scanning/
Soil structure/
Soil pore/
Soil aggregates/
Water parameter
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