冬季咸水结冰灌溉对河套重盐碱地改良效果研究

采用田间大区试验,连续3年在河套重盐碱区开展了冬季咸水结冰灌溉试验研究,设置冬季咸水结冰灌溉(FSWI)和无灌溉对照(CK)两个处理,其中FSWI处理的灌水量为180 mm,矿化度为6.79～7.97 g·L~(–1),种植作物为青贮玉米,以分析不同处理下土壤水盐和钠吸附比(SAR)的周年动态以及对作物生长的影响,探究冬季咸水结冰灌溉对河套重盐碱地的改良效果。结果表明:与CK相比,FSWI处理显著改变了春季土壤水盐和SAR动态。0～20 cm土层,春季FSWI处理的土壤含水量显著高于CK处理,玉米苗期, FSWI处理的土壤含水量平均为24.3%,显著高于CK的21.6%; FSWI处理的春季土壤含盐量和SAR显著低于CK处理,其中, FSWI处理的土壤含盐量由灌溉前的33.86 g·kg~(–1)降低至玉米苗期的5 g·kg~(–1)以下,而CK处理土壤含盐量逐渐升高至玉米苗期的34.2 g·kg~(–1); FSWI处理土壤SAR由灌溉前的21.9降低至玉米苗期的9.86, CK土壤SAR则逐渐升高至玉米苗期的25.00。后续地膜覆盖和夏季降雨使FSWI处理的土壤含水量维持在23.0%以上,土壤含盐量保持在5 g·kg~(–1)以下,土壤SAR保持在9左右。20～40 cm土层与0～20 cm土层的土壤水盐和SAR变化趋势与表层一致,但没有表层变化剧烈。此外,随着灌溉年限的延长,同时期土壤含盐量和SAR呈逐年降低的趋势。FSWI处理玉米出苗率在70%以上,干物质产量为9～12t·hm~(–2),而CK处理由于土壤含水量较低(21.0%),并且土壤含盐量和SAR均较高,造成玉米出苗率极低,进而导致绝收。因此冬季咸水结冰灌溉改变了土壤水盐动态过程,变春季积盐为脱盐,显著降低了土壤SAR,并补充了土壤水分,保证了饲用玉米的正常种植和生长,这为该地区盐碱地改良和饲料作物种植提供了技术支持。

Reclamation effect of freezing saline water irrigation in winter season on the heavy saline-alkali soil in Hetao Irrigation District

A three-year experiment of freezing saline water irrigation in winter season was conducted in a heavy saline-alkali area in Hetao Irrigation District. Two treatments, freezing saline water irrigation (FSWI) and no irrigation (CK), were implemented; the saline water irrigation amount was 180 mm with a salinity of 6.79-7.97 g·L^-1 in the FSWI treatment, and the planting crops were silage maize. This study aimed to analyze the effects of freezing saline water irrigation on the seasonal dynamics of soil water and salt and maize growth and to evaluate the reclamation effect of freezing saline water irrigation on the saline-alkali soil in Hetao Irrigation District. The results showed that, compared with CK, the FSWI treatment significantly changed the soil water, salt, and sodium adsorption ratio (SAR) dynamics in the spring. In the 0-20 cm soil layer of the FSWI treatment, till the seedling stage of maize, the mean soil water content (24.3%) were significantly higher than that under CK treatment (21.6%) in spring. The soil salt content and SAR level under FSWI treatment were significantly lower than those under CK treatment. Under FSWI treatment, the soil salt content was decreased from 33.86 g·kg^-1 before irrigation to <5 g·kg^-1 during the seedling stage of maize, while under CK treatment, the soil salt content was kept at 34.2 g·kg^-1. The soil SAR level under FSWI treatment was decreased from 21.9 before irrigation to 9.86 during the seedling stage of maize, while it was 25 during the seedling stage under CK treatment. Plastic film mulching and subsequent rainfall in the summer maintained the higher soil water content (>23.0%) and lower soil salinity (<5 g·kg^-1) and lower SAR level (<9) in the FSWI treatment. The trends for soil water, salt, and SAR in the 20-40 cm layer were similar to but not greater than those in the 0-20 cm layer. Under FSWI treatment, the emergence rate of maize was >70%, and the biomass of maize was 9-12 t·hm^-2. Moreover, the soil salt content and SAR level in the same season decreased with increasing years of saline water irrigation. The lower soil water content, higher soil salt content, and SAR under CK treatment led to a lower emergence rate and maize biomass. Therefore, freezing saline water irrigation in winter season significantly changed the natural dynamics of soil water and salt; soil salinization decreased as salt leaching combined with a significant decrease in soil SAR and an increase in the soil water content by infiltration of meltwater which ensured normal planting and maize growth. This technology may support the reclamation of saline-alkali soil and forage grass plantation in the area.