Abstract: To explore the difference of soil salinity and nutrients among farmland abandoned,farmland planted spring-sowing crops and pastures in irrigated areas along the Yellow River in Gansu Province,the experiment took bare land (CK),farmlands planted with Triticum aestivum or Elymus nutans / Medicago sativa as the research objects,and measured vegetation coverage,height and biomass,moisture,salt,organic matter and nitrogen of soil for 4 years. The results showed that the salinity difference of wheat land and bare land was not significant when the salinity deposition of topsoil (0～5 cm) happened serious in spring and autumn,while the salinity in forage mixtures land was 52.8% and 55.2% lower in spring,32.7% and 38.6% lower in autumn than those in wheat and bare land,respectively. The salinity of wheat land and bare land decreased with the deepening of the soil layer,while the salt contents of all layers in mix pasture land were low and fluctuated slightly. The topsoil organic matter showed an increasing trend year by year in bare land,wheat land and pasture land. Compared to the autumn of the fourth year with the spring of the first year,the topsoil organic matter content in bare land,wheat and pasture land increased by 21.9%,33.1% and 63.6%,respectively. The change of total nitrogen and hydrolyzed nitrogen in topsoil was different from that of organic matter,and it decreased first and then increased. In conclusion,planting spring wheat with short growth period would cause salt accumulation of topsoil in spring in irrigated areas along the Yellow River in Gansu Province,while planting legume-grass mixtures with longer growth period could effectively restrain salt accumulation and improve soil fertility.

Key words: Irrigated areas along the Yellow River in Gansu Province, Soil salinization, Soil fertility, Farmland ecological conservation

摘要： 为探究甘肃沿黄灌区耕地弃耕撂荒、种植春播作物和牧草对土壤盐分和养分影响,本研究以裸地(CK)、种植小麦(Triticum aestivum)、混播披碱草(Elymus nutans )/苜蓿(Medicago sativa)地为研究对象,连续4年测定植被盖度、高度和生物量及土壤含水量、盐含量、有机质和氮含量等指标。结果表明:表土(0～5 cm)积盐严重的春、秋季节,麦地与裸地盐含量差异不显著,混播披碱草/苜蓿地盐含量比麦地和裸地春季低52.8%和55.2%,秋季低32.7%和38.6%;随土层加深,麦地和裸地盐含量减小,牧草地各土层盐含量均较小且呈小幅波动;裸地、麦地和牧草地表土有机质随种植年限延长呈增加趋势,第4年秋季较第1年春季分别提高21.9%,33.1%和63.6%;而表土全氮和水解氮含量呈先下降、后升高趋势。综上,甘肃沿黄灌区种植生育期较短的春小麦易造成耕地春季表土积盐,而种植生育期较长的豆禾混播牧草可抑制表土积盐和提高土壤肥力,改善土壤质量。

关键词: 甘肃沿黄灌区, 土壤盐渍化, 土壤肥力, 农田生态保育