东北苏打盐碱区浅密沟布设对农田控盐降碱的影响

Influence of Shallow and Densely Spaced Open Ditches on Soil Salinity Control and Alkali Reduction in Soda-saline Farmlands of Northeast China

摘要:

为揭示东北苏打盐碱地在浅密沟排水条件下水盐运移特征与控盐降碱效应，本研究以黑龙江省大庆市典型苏打盐碱农田为对象，设置浅密沟排水与无沟对照2种处理，监测0~100 cm土层含水率、含盐量、pH值、交换性钠离子含量及交换性总阳离子含量等指标，通过结构方程模型量化土壤指标交互效应。结果表明，浅密沟布设显著改变了土壤剖面水盐分布特征，耕层（0~40 cm）含水率显著高于深层，开沟后0~100 cm土层含水率普遍提高，波动范围扩大。开沟区，田间含盐量变化趋势明显，6~10月总体呈现"降-升-降"的变化规律。6月田间平均含盐量降至7.18 g/kg，较开沟前下降46.97%;7月均值为9.00 g/kg，较开沟前降低33.53%;8月降至7.74 g/kg，较开沟前降低42.84%;9、10月保持8.00~9.00 g/kg。开沟后田间含盐量总体水平明显降低，且各时期均表现出较为稳定的降低幅度。6月开沟区碱化度较开沟前下降35.56%，无沟区较开沟前上升17.27%。7~10月，开沟区碱化度稳定在23.23%~37.17%，低于无沟区41.52%~52.58%。结构方程路径分析表明开沟措施增强了降雨对土壤水分的补给与盐分淋洗作用，缓解了田间含盐量、碱化度与pH值的协同增强趋势，蒸发表现出抑制碱化的效应。综合研究结果表明，在松嫩平原盐渍化雨养旱田，采用浅密沟措施能有效降低土壤盐分表聚和碱化度加重风险，实现盐碱土可持续利用。

Abstract:

Aiming to reveal the characteristics of water and salt transport and the effects of salt control and alkali reduction in soda saline-alkali land of Northeast China under shallow dense ditch drainage, the experiment was conducted in a typical soda saline-alkali farmland in Daqing City, Heilongjiang Province. Two treatments were set up, including the shallow dense ditch drainage treatment and the non-ditched control (CK). Indicators such as soil water content (SWC), soil salt content (SSC), pH value, exchangeable sodium ion (Na+) content, and total exchangeable cations content in the 0~100 cm soil layer were monitored, and the interaction effects among soil indicators were quantified by using a structural equation model (SEM). The results showed that the installation of shallow dense ditches significantly altered the water and salt distribution characteristics of the soil profile. The SWC of the plow layer (0~40 cm) was significantly higher than that of the deep soil layer. After ditching, the SWC of the 0~100 cm soil layer was generally increased, with an expanded fluctuation range. In the ditched area, the field soil salinity showed a distinct dynamic trend, which generally followed a "decrease---increase---decrease" pattern from June to October. In June, the average field SSC was decreased to 7.18 g/kg, a 46.97% reduction compared with the pre-ditching level;the average SSC reached 9.00 g/kg in July, 33.53% lower than that before ditching;it dropped to 7.74 g/kg in August, a 42.84% reduction from the pre-ditching level, and remained at 8.00~9.00 g/kg in September and October. The overall level of field soil salinity was significantly reduced after ditching, with a relatively stable reduction magnitude in each period. In June, the exchangeable sodium percentage in the ditched area was decreased by 35.56% compared with the pre-ditching level, while that in the non-ditched control area was increased by 17.27%. From July to October, the ESP in the ditched area stabilized at 23.23%~37.17%, which was consistently lower than the recorded value of 41.52%~52.58% in the non-ditched control area. SEM path analysis revealed that the ditching measure enhanced the replenishment of soil water by rainfall and the salt leaching effect of rainfall, alleviated the synergistic increasing trend of field soil salinity, ESP and pH value, and evaporation exhibited an inhibitory effect on soil alkalization. Comprehensive research results indicated that the application of shallow dense ditch measures in saline rain-fed dry farmland of the Songnen Plain can effectively reduce the risk of soil salt surface accumulation and the aggravation of soil alkalization, thus realizing the sustainable utilization of saline-alkali soil.