暗管排水与节水灌溉条件下盐渍化农田水盐分布特征

灌溉淋洗压盐系盐碱地改良的主要措施,但同时也会造成地下水上升,带来随作物生育期逐渐出现的土壤耕层的返盐现象,其与暗管排水结合则可提高脱盐效果。为了研究暗管排水条件下的油葵在拔节期增加不同的灌水量对盐碱地(施加30 t/hm~2脱硫石膏,土壤耕作层掺入85.05 m~3/hm~2细沙)土壤水盐及土壤酸碱性分布的影响,设计了暗管排水结合传统灌溉处理、暗管排水结合节水灌溉处理、暗管排水结合无灌水对照处理3种处理,通过监测土壤EC值、pH、含水率,分析暗管排水结合传统灌溉与节水灌溉对重度盐碱地土壤的水分、盐分及酸碱程度的时空变化特征。结果表明:与对照处理对比,传统畦灌方式下灌水处理降低了土壤含水率,对0～20 cm土层的脱盐效果明显;在暗管排水的基础上,对照处理的油葵地0～60 cm土层的EC值为3.49～0.67 d S/cm,节水灌溉处理的EC值为1.71～0.33 d S/cm,传统灌溉处理的EC值为3.75～0.27 d S/cm;虽然传统灌溉在灌水后10 d左右降低了0～100 cm土壤盐分,提高了土壤的含水率,但传统灌溉处理下油葵在开花期0～40 cm土层的含水率比对照处理低,且40～100 cm土层的返盐程度是节水灌溉的2～3倍;对照处理下0～60 cm土层的pH为7.54～8.65,节水灌溉处理下pH为7.51～8.89,对照处理下40～100 cm土层的pH为8.29,传统灌溉处理下pH为8.1～10.85,节水灌溉处理的土壤在0～100 cm的土层呈现脱碱的状态,高的灌水量使土壤有碱化的可能,尤其是在20～40 cm土层。暗管排水条件下在油葵拔节期进行节水灌溉有利于土壤脱盐、脱碱。

Distribution characteristics of water and salt under closed saline drainage pipe and water-saving irrigation in saline soils

Irrigation, leaching and salt pressing are the main measures for the amelioration of saline and alkaline land, but these measures also cause the phenomenon of salt return in soil plough layer due to the rise of groundwater. With the combination of closed drainage pipes, the desalination effect can be improved. In order to study the effect of different irrigation amount on soil water, salt and soil acidity and alkalinity distribution in saline and alkaline soil (with 30 t/hm² desulfurized gypsum and 85.05 m³/hm² fine sand mixed into soil tillage layer), under the condition of closed pipe drainage, three treatments were designed, namely, closed drainage combined with traditional irrigation, closed drainage combined with water-saving irrigation, and closed drainage combined with non-irrigation control treatment. By monitoring soil EC, pH and water content, the temporal and spatial variation characteristics of soil moisture, salinity and degree of acid and alkali were analyzed by combining traditional irrigation and water-saving irrigation with closed drainage. The results showed that compared with the control treatment, the traditional border irrigation treatment reduced soil moisture content, and the desalination effect of 0-20 cm soil layer was obvious. On the basis of closed drainage, EC values of 0-60 cm in oil sunflower field were 3.49- 0.67 dS/cm, 0-60 cm were 1.71- 0.33 dS/cm for water-saving irrigation and 3.75- 0.27 dS/cm for traditional irrigation. Although the conventional irrigation decreased soil salt in 0-100 cm soil layer after 10 D and increased the water content, the soil water content of 0-40 cm was still lower than that of the control treatment. Desalination effect of 40-100 cm soil layer was 2-3 times higher than that of the water-saving irrigation. The pH of 0-60 cm soil in the control treatment was 7.54-8.65, and 7.51-8.89 in water-saving irrigation treatment, which was close to that in the control treatment at 40-100 cm (8.29). The traditional irrigation treatment was 8.1-10.85, and the soil layer of 0-100cm in the water-saving irrigation treatment was dealkalized. High irrigation amount made the soil alkalization possible, especially in the soil layer of 20-40 cm. Under the condition of closed drainage, water-saving irrigation in the jointing stage of oil sunflower is conducive to soil desalination and dealkalization.