荒漠草原绿洲化过程中灌溉玉米地土壤夏季盐渍化特征

Summer Salinization Characteristics of Irrigated Corn Cropland During Oasisization of Desert Steppe

在地处宁夏中部荒漠草原区的红寺堡扬黄灌区,选取不同利用年限的灌溉玉米地,以临近的未利用地为对照,对其夏季含盐量及盐离子组分变化规律、剖面分布类型、时空相关性及其碱化特征进行了系统分析。结果表明,在退化草地转化成灌溉农田的过程中,土壤夏季含盐量剖面分布变化依次为表聚型、均匀型(震荡型)和底聚型。未利用地0-60 cm土层总含盐量6.0‰,耕种8年后只有2.25‰,表层(0-20cm)的总盐含量降幅高达80.2%。未利用地盐分表聚特征主要由氯离子、镁离子、钙离子和钾离子决定,其浓度随利用年限的变化表现较为平稳,剖面分布以均匀型为主,而硫酸根离子和钠离子底聚特征明显。相对未利用地,重碳酸根离子是唯一全剖面出现明显增加的离子类型。离子间显著相关关系多集中于0-40 cm土层发生,相关格局随利用年限发生明显变化,8年玉米地重碳酸根离子和钠离子正相关、钙离子与钠离子以及重碳酸根离子间负相关关系凸显。土壤碱化表现出明显的阶段性发生(2年玉米地)和下迁富集发生(40-80 cm)特征,8年玉米地含盐量和碱化度同步显著下降,土壤盐渍化整体逆转。灌溉玉米地土壤含盐量与碱化度显著正相关,未利用地含盐量与碱化度则呈现两极化分布趋势。灌溉玉米地土壤夏季盐渍化特征受土壤-植物的相互作用控制,蒸发积盐、蒸腾积盐与灌溉脱盐作用并存,盐离子分化明显,土壤盐化和碱化时空同步变化,但是总碱度居高不下依然是威胁土壤环境健康的潜在因素。

The soil of irrigated corn croplands with different farming years,in Hongsibu yang-huang irrigation area in Ningxia central profiles（degenerated desert steppe）,were sampled and tested to analysis their evolution,profiles distribution,space-time correlation for the salt contents and salt ions and the basification characters in summer.During the oasisization of desert steppe,the profiles distribution of soil salt contents changed from surface-gathering,to uniformity or vibration,at last to bottom-gathering ones.The total salt contents of 0-60 cm soil profiles was 6.0‰ for the unused lands,however,the contents dropped to 2.25‰ for the 8-year corn-land with 80.2% drops at the surface soil（0-20 cm）.The surface-gathering of soil salt contents for the unused lands was mainly controlled by the ions of Cl^-,Mg^2＋,Ca^2＋,and K^＋,their contents less changed and kept uniformity profiles-distribution during the oasisization of desert steppe,but the ions of SO4^2- and Na^＋ mainly enriched at the bottom.Compared with the unused lands,HCO3^- was the only ion to increase markedly at the whole soil profiles（0-80 cm）.The correlation among different ions occurred mainly at the 0-40 cm soil profiles,with marked changes during the oasisization of desert steppe,especially,the positive correlations between HCO3^- and Na^＋,the negative ones among Ca^2＋,HCO3^- and Na^＋,occurred only for the 8-year corn-lands.The soil basification put up of typical phased（2-year corn-lands） and bottom-gathering（40-80 cm soil profiles） occurring characters,and the salinization for 8-year corn-lands were whole reversed with in-phase dropping of TS and basification degrees（ESP）.There were markedly positive correlations between the TS and ESP for the irrigated corn-lands,however,the relation for the unused lands disappeared,with the polarization of surface salinazition and bottom basification.In conclusion,the salinization characters of irrigated corn-lands are controlled by the reciprocity between soils and plants,with the together acts of evaporation,transpiration and irrigation,the soil salinization and basification change in-phase in spacetime scales,however,the total soil basicity still in higher levels potentially threatens the soil environment health.