Design and experiment of protective blanket for soil salination control

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.