黑土区起垄耕作对物理结皮孔隙发育特征及土壤入渗的影响

    Effects of ridge tillage on physical crust pore characteristics and soil infiltration in the black soil region

    • 摘要: 为探究东北黑土区起垄耕作对物理结皮孔隙发育特征及土壤入渗的影响,该研究以未起垄和2种起垄方向下(横坡起垄、顺坡起垄)形成的结构性结皮和沉积性结皮土壤为研究对象,分别于2023年5月和9月进行采样和原位入渗试验,通过CT扫描技术系统分析了结皮发育引起的土壤微观孔隙变化,并量化了结皮特征和入渗的关系。结果表明:1)横坡起垄促进了沉积结皮的发育,垄沟中 > 0.25 mm的水稳性团聚体占比上升17.80%。起垄促进了颗粒分选,表现为沉积结皮中粉粒的富集,较未起垄处理下平均增加12.57%;横坡起垄形成的结皮中黏粒含量较高,而顺坡起垄下结皮层黏粒损失了17.10%。2)横坡起垄下的结皮层孔隙率随发育时间而增加且孔隙大小逐渐趋近,孔隙率由结皮表层向下呈现递增趋势;顺坡起垄下结皮土壤孔隙出现双重封闭现象,沉积结皮的喉道数量显著减少且有较多孤立孔隙形成;未起垄条件下结皮层的大孔隙结构被更好的保留。3)结皮土壤平均入渗率表现为未起垄处理(0.58 mm/min)> 横坡起垄(0.15 mm/min)> 顺坡起垄(0.11 mm/min)。初始入渗率主要受表层结皮容重和下层容重调控,而稳定入渗率由结皮厚度和大团聚体影响下的孔隙结构所主导。通过影响不同类型结皮的形成,起垄措施对土壤入渗具有重要调控作用,顺坡起垄时需要减少垄沟因压实作用而形成的结皮以增加土壤水分入渗。研究结果可以为研究区合理垄作以促进水分入渗,提升土壤质量提供参考。

       

      Abstract: To investigate the effects of ridge tillage on physical crust pore development characteristics and soil infiltration in the black soil region of Northeast China, this study took crusted soil formed under non-ridging and the structural crust and sedimentary crust soil under two ridge directions (contour ridge tillage and downslope ridge tillage) as research objects. Sampling and in-situ experiments were conducted in May and September 2023, respectively. The changes in soil micro-pores caused by crust development were systematically analysed through CT scanning technology and in-situ infiltration experiments, and the relationship between crust characteristics and infiltration was quantified. The results showed that ridge tillage leads to the differentiation of crust characteristics between ridges and furrows. Contour ridge tillage promoted the development of sedimentary crust, and the proportion of water-stable aggregates in the furrows increased significantly. Longitudinal ridge tillage intensified the sorting effect of runoff on soil particles. The porosity of the crust layer under contour ridge tillage increased with time and the pore size gradually approached. The porosity showed an increasing trend from the crust surface to the subsoil layer. The soil pores of the crust under longitudinal ridge tillage showed a double closure phenomenon, the number of throats in the sedimentary crust decreased significantly while more isolated pores were formed. Under this condition, the stronger concentrated runoff in the furrows drastically reduces sediment particles, resulting in the sedimentary crust being thinner than that formed under contour ridge tillage. The large pore of the crust layer was better preserved under non-ridging conditions. The average infiltration rate of crust soil ranked as non-ridging (0.58 mm/min) > contour ridge tillage (0.15 mm/min) > longitudinal ridge tillage (0.11 mm/min). Ridge tillage mainly regulates soil infiltration by forming different types of crusts. After the formation of crusts, the soil water-holding capacity increases, allowing the soil more rapidly to reach saturation. The high proportion of capillary pores in crusted soil prolongs water retention time, leading to a significant decline in the infiltration of crusted soil. The initial infiltration rate is mainly controlled by the bulk density of the surface crust and subsoil, while the steady infiltration rate is primarily dominated by the pore structure influenced by crust thickness and water-stable aggregates. The formation of different types of crusts induced by ridge tillage is the main pathway affecting the infiltration rate. Under contour ridge tillage conditions, the pore networks are more developed. By improving soil porosity, the soil infiltration capacity is correspondingly enhanced. The bulk density and saturated water holding capacity of the subsoil, as well as the WSA> 0.25 and thickness of the crust layer, can effectively predict the initial infiltration rate and steady infiltration rate of crusted soil, respectively. The results can provide important theoretical support for reasonable ridge tillage practices to reduce soil erosion.

       

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