土壤盐渍化治理防护毯的研发及试验

    Design and experiment of protective blanket for soil salination control

    • 摘要: 土壤盐碱化问题是中国农业面临的一个巨大挑战,严重制约着农业生产的发展。为探索治理土壤盐渍化的方法,该文基于干旱区5类代表性土壤(砾砂、粉土/粉砂、粉土/粉细砂、粉土和亚黏土)的盐碱化规律,以盐碱土形成原因为切入点,结合土壤水的毛细管作用,以海绵(强力吸水层)、吸热聚乙烯编织布(蒸散加强层)为主要材料,设计出一种盐碱地治理防护毯,并对防护毯吸盐的深度和效果进行试验研究。结果表明:5类土壤表面的积盐情况各不相同,粗颗粒土(砾砂及砂土)含量较大时,在强蒸发条件下,3~4 d土样表面积盐后形成了一层厚约3~4 mm"盐痂";细颗粒土(亚黏土和粉土)含量相对较多时,短期内表面积盐速度相对较慢且现象也不明显,10~12 d后,土样表面可观察到一层细密的晶体盐颗粒。所以,土壤岩性质地与表层积盐量关系密切。总体趋势是:土壤颗粒越粗,土壤表层在早期的积盐量越大;土壤颗粒越细,土壤表层在后期的总体积盐量越大。在干燥通风和室外温度25℃的条件下,防护毯针对上述不同类型土壤进行吸盐试验,在4 d后0~10 cm土层的含盐量(质量分数,下同)均可减少80%(P<0.05)以上;>10~20 cm土层至少减少50%(P<0.05)以上;对于砂性土来说,>20~30 cm土层含盐量减少了50%左右(P<0.05),而黏性土和壤土可减少20%~30%以上(P<0.05)。对于实际中的盐碱土而言,含盐量减少30%时,土壤的肥力和可耕作程度会明显改善,能有效减小盐碱化对作物生长的影响。此外,研究还发现,铺设防护毯还能改变盐碱地表层土壤的结构,增强土壤的透气性。防护毯最佳使用时间应为土壤毛细管作用最强烈的时间段。该研究提供了一种有效的盐碱地治理措施。

       

      Abstract: Abstract: Soil salinization is a great challenge for Chinese agriculture, severely crippling the development of agricultural production. Soil salinization is often caused because strong evaporation and capillary transport salt ions to soil surface. Probably, the salt removal from soil surface by materials with strong capillary is a way to control salinization. In this study, we investigated the cause of saline-alkali formation of 5 types of soils in droughty areas, and proposed a protection blanket for soil salinization control based on the principle of soil capillary and tested its feasibility of control soil saline in 5 soils. The blanket was composed of sponge (stronger absorbent layer) and endothermic polyethylene weaved cloth (sforzato evaporation layer). The soil salt ions were absorbed by sponge into the outer cloth so that the salt could not accumulate on the surface of the soil. The blanket was used in 5 soils with different textures (gravel, silt/silt sand, silt/fine sand, silt, mild clay). The soils were collected from Fangcao Lake farmland, Hutubi county, Xinjiang (43°16′-45°20′N, 86°05′-87°07′26″E), and air-dried to mix with salt solution made of 36 g/L NaCl, 34 g/L KCl, and deionized water. The soils were filled into a box with area of 1 m2 (30 cm depth to simulate tillage layer). The initial soil moisture was 12% and soil compactness was 0.8. The salt content of soils at 5 cm was determined destructively at 4, 12 and 20 d. The salt accumulation on soil surface was photographed. Meanwhile, another soil samples with salt water were placed in columns in 40-cm length and 20-cm diameter and 30-cm depth with blanket covered for measurements of salt-absorption dynamics and depth of the blanket. The results showed that: 1) The salt distribution on soil surface varied with soil texture and the salt crystals were much more in the coarse-grained soil (gravel sand and sand) with about 3-4 mm depth in 3-4 days than the fine granular soil (clay and silt) with salt accumulation at a comparatively low rate so that crystal salt could not observed in 10-12 days; 2) The salt accumulation was obvious in early stage of experiment in the coarse soil particles but in the later stage of experiment in the fine soil particles; 3) The blanket could reduce salt content in 0-10 cm soil layer by more than 80% (P<0.05), and reduce in 10-20 cm by more than 50% (P<0.05) after 4 days under the condition with the outdoor temperature of 25℃ and dry ventilation allowed; Using the blanket, the salt content in 20-30 cm depth could be reduced by more than 50%, and more than 20%-30% (P<0.05) for sandy soils, clay and loam soil, respectively. For practical application, the salt content reduction of 30% can greatly improve soil fertility and cultivability, and effectively alleviate the impact of salinity on the growth of crops. The results above indicate that the protective blanket is an effective measure for saline-alkali land amelioration. Theoretically, its effect should be best when soil capillary is strongest. However, its feasibility still need to be validated in more studies and in fields.

       

    /

    返回文章
    返回