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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)起垄促进了颗粒分选,表现为沉积结皮中粉粒的富集,横坡起垄和顺坡起垄较未起垄处理下的粉粒占比分别增加1.98%和10.88%;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%。横坡起垄促进了沉积结皮的发育,结皮中 > 0.25 mm的水稳性团聚体占比上升17.80%。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由大到小依次为未起垄处理(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。研究结果可以为合理垄作以促进水分入渗,提升土壤质量提供参考。

     

    Abstract: This study aims to investigate the effects of ridge tillage on physical crust pore characteristics and soil infiltration in the black soil region of Northeast China. Research objects were taken as the crusted soil under non-ridging, as well as the structural crust and sedimentary crust soil in two ridge directions (contour and downslope ridge tillage). Sampling and in-situ experiments were conducted in May and September 2023, respectively. A systematic analysis was conducted to determine the variations in soil micro-pores during crust development using CT scanning technology and in-situ infiltration experiments. The results showed that ridge tillage caused the differentiation of crust characteristics between ridges and furrows, according to the relationship between crust characteristics and infiltration. Contour ridge tillage promoted the development of sedimentary crust, with the increasing proportion of water-stable aggregates in the furrow. Longitudinal ridge tillage also intensified the sorting effect of runoff on soil particles. The porosity of the crust layer increased with the time under contour ridge tillage, where the pore size approached gradually. The porosity showed an increasing trend from the crust surface to the subsoil layer. The soil pores of the crust shared a double closure under longitudinal ridge tillage. The number of throats in the sedimentary crust decreased significantly to form the more isolated pores. The more concentrated runoff in the furrows drastically reduced the sediment particles. As such, the sedimentary crust was thinner than that 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 was ranked in the descending order of the non-ridging (0.58 mm/min) > contour ridge tillage (0.15 mm/min) > longitudinal ridge tillage (0.11 mm/min). Ridge tillage regulated the soil infiltration to form the different types of crusts. The soil water-holding capacity rapidly increased with soil saturation after the crust formation. The water retention time was prolonged under the high proportion of capillary pores in crusted soil, leading to a significant decline in the infiltration of crusted soil. The initial infiltration rate was controlled by the bulk density of the surface crust and subsoil, while the steady infiltration rate was primarily dominated by the pore structure, subject to the crust thickness and water-stable aggregates. Different types of crusts with ridge tillage were the main influencing factors on the infiltration rate. The pore networks were more developed under contour ridge tillage. Correspondingly, soil porosity improved the soil infiltration. The initial and steady infiltration rates of crusted soil were effectively predicted using bulk density and saturated water holding capacity of the subsoil, while the WSA> 0.25 and the thickness of the crust layer. The findings can also provide important theoretical support for the optimal ridge tillage to reduce soil erosion.

     

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