绿洲灌区固定道耕作对土壤盐分动态的影响

Effects of permanent raised beds on soil salinity in oasis irrigation districts

  • 摘要: 解决节水灌溉与控制土壤次生盐渍化的矛盾, 对干旱内陆绿洲灌区农田节水、防止土壤次生盐渍化和保证绿洲农业稳定持续发展具有重要意义。本研究以传统翻耕(CT)、垄作沟灌(FRB)、固定道保护性耕作(PRB)和固定道平作(ZT)4种耕作方式为研究对象, 研究了固定道耕作模式下的土壤盐分特征。结果表明: 与播前相比, 收获后FRB处理0~20 cm、20~40 cm、40~60 cm和60~100 cm土层土壤含盐量分别提高83.3%、77.2%、47.6%和84.0%, PRB处理分别提高62.6%、46.3%、28.2%和103.6%。ZT和CT处理0~200 cm土壤含盐量呈“脱盐”和“聚盐”交替变化趋势, 0~60 cm各土层土壤含盐量随灌水显著降低, 而60~200 cm各土层土壤含盐量随灌水显著增加。0~20 cm、20~40 cm和40~60 cm土层是PRB和FRB处理土壤盐分的主要累积区, ZT和CT处理土壤含盐量随灌水最终积累在100~160 cm土层。从头水后至收获各个时期, PRB处理0~200 cm各土层土壤含盐量均高于FRB处理, 且差异显著。ZT处理0~20 cm、20~40 cm、40~60 cm和60~100 cm土层土壤含盐量均显著高于CT处理。垄床不同位置土壤盐分运动水平方向上均呈“垄边向垄中”迁移特点, 但PRB处理迁移能力强于FRB处理。垂直方向上, FRB处理在土壤60~80 cm处形成积盐峰, 而PRB处理在土壤40~60 cm处形成积盐峰。随灌溉水分入渗再分布后FRB处理土壤盐分向垄沟中部和垄床表层迁移, PRB处理土壤盐分在垄床40~60 cm土层处形成一个积盐层。结果说明, 垄作方式能显著增加土壤剖面盐分累积。随着垄作年限增加, 盐分向垄床中部积累的能力和含量均增强, 由此垄作种植应考虑适时漫灌以达到淋洗土壤盐分的目的。

     

    Abstract: Shortage of water resources and soil salinization threaten oasis agriculture ecosystem health and stability, which are the two big problems in sustainable agricultural development in arid oasis irrigation areas. While there is need to adopt new irrigation technologies in these regions, such actions could break up the balance of soil water and salt. This could eventually cause secondary soil salinization of farmlands that will in turn decrease farmland productivity. To develop new water-saving irrigation technologies, prevent secondary soil salinization and ensure sustainable agricultural development in irrigated arid oasis areas of Northwest China, it is important to resolve existing conflicts between the adoption of water-saving irrigation technology and the control of secondary soil salinization. Thus an experiment was conducted in spring wheat fields from 2005 to 2010 to monitor soil salinity characteristics under conventional tillage (CT), fresh raised-bed (FRB), permanent raised-bed (PRB) and zero-tillage in flat fields (ZT, control). The results showed that soil salt content increased from sowing to harvest under FRB by 83.3% in the 020 cm, 77.2% in the 2040 cm, 47.6% in the 4060 cm and 84.0% in the 60100 cm soil layers. For the same layers under PRB treatment, soil salt content increased by 62.6%, 46.3%, 28.2% and 103.6%, respectively. Main salt accumulation zone under furrow irrigated FRB and PRB treatments was the 060 cm soil layer. However, main salt accumulation was the 100160 cm soil layer under flood irrigated ZT and CT treatments while there was alternative soil desalination and accumulation in the 0200 cm soil profile. Soil salt content in the 060 cm soil layer decreased with decreasing irrigation while it increased with decreasing irrigation in the 60200 cm soil layer. Soil salinity in root-layer soil depth (0200 cm) was significantly greater from first irrigation to harvest under PRB treatment than under FRB treatment. There was soil salt accumulation in the 6080 cm soil layer under FRB treatment and in the 4060 cm soil layer under PRB treatment. Soil salinity was significantly greater under ZT than CT treatments in the 0100 cm soil layer. Following normal irrigation, soil salinity became redistributed in the middle and surface of beds under FRB treatment. Soil salt migration from the edge to the center of the beds was most notable under PRB treatment. Ridge tillage and bed farming significantly increased salt accumulation in the soil profile. With increasing number of years of cropping and irrigation, salt increasingly migrated and accumulated in the middle of the beds. Thus a fraction of the irrigation water leached salts from ridges/beds and from the soil profile. There was need for at least one irrigation to be larger than normal (over the top of the beds) to enhance redistribution of salts below root-zone soil layer.

     

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