干旱区农田不同类型土壤盐碱化发生规律

Soil salinization features in arid areas farmland

为明晰西北干旱区平原农田典型土壤发生盐碱化的规律,2014年在新疆代表性平原农场采集砾砂、粉土/粉砂、粉土/粉细砂、粉土和亚黏土5类主要土壤进行试验,分析其岩性组成、毛细管作用及土壤表层积盐之间的内在关系,寻求3者相互影响机理。结果表明:土壤中粗颗粒含量越大,早期毛细管现象越明显,土壤表面积盐越多。细颗粒含量越多,早期毛细管作不明显,地表积盐量较少但持续时间较长,最终积盐量大于粗颗粒土壤。5类土壤在盐碱化发生早期(12 d左右)毛细现象最为突出,尤其1~4 d内地表的积盐大,速度最快。粗颗粒的砂性土发生盐碱化时,表面容易形成3~4 mm厚盐痂,阻止了地表盐碱化的发展。当土壤中粉粒和黏粒较多时,地表积盐主要以晶体形式出现。土壤的颗粒级配较好、压实度较大时,土壤表面的积盐量就较少。研究成果可为西北地区不同类型的土壤盐碱化治理方法、治理时段的选取等提供参考。

Xinjjiang is the biggest drought and saline area in China and soil salinization is of unique characteristics. In order to find features of soil salinization in arid area of northwest plains in China, in this study, we sampled from typical farmland in Xinjiang and carried out a series of laboratory experiment. Five soil samples were collected from the farmland for determination of their particle composition, and permeability coefficient. Based on these, the soils were classified into gravel, silty sand, fine sand, silt and loam. The rising height of capillary water from these soils with tap water as water resource was measured in 20 days of experiment. In another experiment, the salt accumulation was observed with NaCl and KCl in water as salt resources. The salinity in soil 5-cm depth was determined. The soil lithology, rising height of capillary water, and salinity were analyzed for their relationships. The results showed that the rising height of capillary water was fast in the first 12 days of experiment, and it was faster in soils with coarse particles. Meanwhile, the salt accumulation in soil 5-cm depth was obvious. However, the salt accumulation in soils with more fine particles could last for a longer period than those with coarse particles. In the end of experiment, the salinity in soils with coarse particles was smaller than that in fine particle-dominated soils. The rising height and rate of capillary water were most obvious in the first 3-4 days, which may indicate the control of saline soils should be in the early stage. In addition, the sandy soils were accessible to salt scale in 3-4 mm thickness, which may clog the capillary and prevent from the development of salinization. But, the thick salt scales also lead to difficulty in control of saline soils and they should be destroyed by surface ploughing. The results provide valuble information for understanding and control of soil salinization in arid area.