通过研究不同覆砂年限砂田土壤水分特征和矿质元素变化规律，探索砂田衰退的机理。对可用砂田和废弃砂田的砂土混合层变化、土壤含水量、矿质元素及盐分含量进行了长期定位的分析测定。结果表明，种植1、3、7、15 a砂田砂土比由9.16降低至1.60，而撂荒地为3.59。砂覆盖3 a后土壤平均水分含量较原生地高13.1 mg/g；砂覆盖15 a后土壤0~20、20~40、40~60、60~80、80~100 mm土层含水量比原生地分别高2.4、3.5、4.0、4.4、4.7 mg/g。不同覆砂年限果园0~60 cm土壤有机质、土壤全氮与碱解氮、全磷与速效磷、全钾与速效钾及全盐含量变化随覆砂年限增加均呈先增加后降低的趋势，这与砂田功效及衰退密切相关，也是中老砂田衰退的主要特征。

This study investigated the changes in soil moisture characteristics and mineral elements in gravel-sand mulched fields with different mulching durations to explore the degradation mechanism of gravel-sand mulched fields. Long-term analysis and measurement of the mixed sand layer, soil moisture, mineral elements, and salt content in usable and abandoned gravel-sand mulched fields were conducted in a fixed location. The results showed that the sand-to-soil ratio in gravel-sand mulched fields planted for 1, 3, 7, and 15 years decreased from 9.16 to 1.60, while the ratio in abandoned gravel-sand mulched fields was 3.59. After 3 years of mulching, the average soil moisture content increased by 13.06 mg/g compared to the native land. After 15 years of mulching, soil moisture content in the 0 to 20, 20 to 40, 40 to 60, 60 to 80, and 80 to 100 mm layers was 2.4, 3.5, 4.0, 4.4, and 4.7 mg/g higher than that in the native land, respectively. In orchards with different sand-mulched durations, changes in organic matter, total nitrogen and alkali-hydrolyzable nitrogen, total phosphorus and available phosphorus, total potassium and available potassium, and total salt contents in the 0 to 60 cm soil layer followed a pattern of increasing followed by decreasing with the length of gravel-sand mulching. This trend is closely related to the effectiveness and degradation of gravel-sand mulched fields and represents a major feature of the degradation of middle-aged and old gravel-sand mulched fields.

S158.1

甘肃省农业科学院中青年基金(2014GAAS14)；甘肃省农业科学院区域协同项目(2011-1-151)。