Soil secondary salinization has become the most prominent problem in solar greenhouse cultivation. The utilization method of moistube irrigation, a underground irrigation technology with semi-permeable membrane as the core material to supply slow and continuous water flow to crop root zone in soils should be considered to avoid the secondary salinization. In order to explore the effect of moistube irrigation on secondary salinization soil in solar greenhouse, a field experiment was carried out from October 2015 through April 2016 in a 108-m by 8-m solar greenhouse (E108°02′, N34°17′) in Yangling Agricultural Hi-tech Industries Demonstration Zone, Shaanxi Province, China. A total of 3 soil depths (10, 20, 30 cm) and 3 moistube layouts with different spacing (1 tube with 2 lines, 2 tube with 2 lines, 3 tube with 2 lines, the 2 lines refer to the line of tomatoes) were set up to study the changes of soil water and salt distribution in solar greenhouse. Meanwhile, the mulched drip irrigation was used as control in order to analyze the difference of moistube irrigation from the conventional irrigation method. The open field soil nearby the greenhouse was sampled to investigate the soil salinization degree caused by the greenhouse cultivation. The results showed that the soil salinity in solar greenhouse was significantly higher than that in open field, the average salinity of the cultivated layer (0-20 cm) reached 2.745 g/kg after 5 years of tomato cultivation, which was close to the critical point (2.75 g/kg) of crop growth. The mild soil salinization had been occurred in the tested solar greenhouse soil. Under the CK condition, the soil moisture largely fluctuated in the main root zone. The fluctuation was big but stable at the end of the stage. The soil moisture changed in a similar trend for all the moistube irrigation treatments. The soil moisture increased until 45 days of planting and then decreased slowly. The coefficient of variation in the 0-30 cm depth was larger than 10% for the CK treatment, which was obviously higher than the moistube irrigation. Among all the moistube irrigation treatments, the 3 tubes with 2 lines had the more even soil moisture distribution and the coefficient of variation at the depth of 10 cm was smallest (3.62%). Both the buried depth and moistube layout significantly (P<0.05) affected the soil moistube but they didn't show significant interactive effect (P>0.05). Compared with the CK treatment, moistube irrigation had a high degree of desalination. The average relative desalinization rate of the moistube irrigation was 32.49% at 0-60 cm soil layer and 76.30% in the main root zone (0-30 cm) (P<0.05) higher than that of CK. The buried depth of moistube was an important factor affecting the distribution of soil water and salt, a high water and low salinity zone appeared in the soil layer at the moisture buried depth. It was beneficial to the soil salt leaching in the main root zone (0-30 cm) under shallow buried conditions, and in the minor root zone under deep conditions. The soil salinity was increased at the late growth stage of tomato for the treatment of 30 cm buried depth and 1 tubes with 2 lines, which could exacerbate soil secondary salinization. Considering the characteristics of salt accumulation and tomato root distribution in solar greenhouse, we suggested that 10 cm depth and 3 tube with 2 lines were the best for moistube irrigation with the average relative desalinization rate of 0-60 cm soil layer of 22.27% and the relative desalinization rate of 29.86% in the tomato main root zone. This study can provide valuable information for the application of moistube irrigation in solar greenhouse.%为探求微润灌溉对于日光温室次生盐渍化土壤的影响,设置3种毛管埋深(10、20和30 cm)和3种毛管间距不同的布置(1管2行、2管2行、3管2行,2行指番茄行),以膜下滴灌(CK)为对照,分析日光温室土壤水盐分布的变化.结果表明,日光温室耕层土壤(0~20 cm)平均含盐量达2.745 g/kg,接近阻碍作物生长的临界点(2.75 g/kg),发生了轻度次生盐渍化.与CK比较,微润灌溉具有较高的脱盐效果,0~60 cm土层平均相对脱盐率较CK提高了32.49%,0~30 cm主根区较CK提高了76.30%(P<0.05).可用幂函数较好地描述微润灌溉日光温室番茄主根区土壤盐分随定植后天数的动态变化过程.微润管埋深是影响土壤水盐分布的重要因素,在微润管埋深处土壤形成一个高水低盐区,毛管浅埋有利于主根区土壤(0~30 cm)盐分的淋洗,深埋有利于次根区土壤(>30~60 cm)盐分的淋洗,埋深30 cm,1管2行组合番茄生育末期土壤含盐量有升高趋势,可能会加剧土壤次生盐渍化.结合日光温室盐分累积及番茄根系分布特征,埋深10 cm,3管2行为轻度次生盐渍化土壤适宜的应用模式(该组合综合脱盐效果最好,0~60 cm土层平均相对脱盐率为22.27%,主根区相对脱盐率为29.86%,比CK提高1倍以上).该研究为微润灌溉在日光温室的应用提供参考.
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