| Hetao Irrigation District is a large-scale gravity irrigation area in China,and its main irrigation mode is flood irrigation with water diversion from the Yellow River.The high groundwater level and intensive evaporation lead to the accumulation of soil salinity in the surface,so the aggravation of soil salinization restricts local grain production and sustainable development of agriculture seriously.With the shortage of water resources being more and more serious,the Yellow River Committee has strengthened the unified dispatching of water resources in the Yellow River.The amount of irrigation water from the Yellow River will be reduced from 5.2 billion m3 to 4.0 billion m3,which will intensify the contradiction between water supply and demand in the local.Therefore,exploring the irrigation and drainage modes suitable for the region is one of the most significance for saving water resources,improving soil salinization and increasing crop yield.Through two years of experimental data in the field acquisition and analysis,this paper explored the distribution characteristics of soil moisture and salinity in field scale under drip irrigation and subsurface pipe drainage,and analyzed the effects of drip irrigation and subsurface pipe drainage on farmland drainage and desalination,dynamic variation of groundwater and crop yield.Seeking appropriate irrigation system and pipe spacing in sunflower planting areas under drip irrigation and subsurface pipe drainage,providing reference for the use of water management and the planning and design of water saving,drainage reduction and salinity control projects in Hetao Irrigation District in the future.This experiment was carried out at the Yongji Test Base of China Agricultural University from 2018 to 2019.The planting crop was sunflower YG361,using drip irrigation under mulch and subsurface pipe drainage,with three irrigation quotas(50mm,60mm and 70mm)and two pipe spacing(30m and 45m).The moisture and salinity content of the soil profile,the discharge of the subsurface pipe,the salt discharge and the dynamic changes of the groundwater,and the growth indexes of the sunflower were collected during the whole growth period.The main research contents and results are as follows:(1)According to the experimental data from 2018 to 2019,under different pipe spacing and different irrigation conditions,the moisture content in 0-100cm soil profile showed an increasing trend with the soil depth increasing gradually.The soil moisture content varied from 0.17 cm3/cm3 to 0.46 cm3/cm3,which changed obviously in the surface layer,changed less in the middle layer and changed least in the deep layer.Taking the treatment of 30m spacing and 70mm quota as an example,the moisture content was 0.26?0.34 cm3/cm3 in the surface layer(0-20cm),which was 0.31?0.41 cm3/cm3 in the middle layer(20-60cm)and 0.32?0.46 cm3/cm3 in the deep layer(60-100cm).(2)Under the different pipe spacing and different irrigation quotas,the salinity content in 0-100cm soil profile showed a decreasing trend with the increase of soil depth.The soil salinity content varied from 0.1g/kg to 4.6 g/kg,which was high in the surface layer,which was lower in the middle layer and the least along with stable in the deep layer.Taking the treatment of 30m spacing and 70mm quota as an example,the salt content was 1.8-4.6g/kg in the surface layer(0-20cm),which was 0.38?1.76g/kg in the middle layer(20-60cm)and 0.3.1.51 g/kg in the deep layer(60-100cm).(3)The effect of soil moisture and salinity discharge as well as the soil moisture and salinity in the area of 30m pipe spacing,was better than that in the area of 45m spacing.Under the same pipe spacing,the desalination effect was better with the irrigation quota increasing.The treatment of 30m pipe spacing and 70mm irrigation quota could effectively control the salinity content in 20-100cm soil layer.(4)The drainage data showed that the displacement in the area of the 30m spacing was larger than that in the area of 45m spacing in 2019.The maximum daily drainage in the area of the 30m spacing reached 41m3,and that of the 45m spacing reached 32m3,and the trend of the daily drainage was similar in the areas of 30m and 45m spacing.The drainage salinity in the area of the 30m spacing was lower than that of the 45m spacing,and the drainage salinity in the area of 30m pipe spacing was 0.91?1.04g/L,and that of the 45m spacing was 1.07?1.2g/L.Therefore,the effect of soil moisture and salinity discharge in the area of 30m spacing was better than that of 45m spacing.(5)The variable trends of plant height were similar in different treatments during two years of field experiment,so was stem diameter.There was no significant difference in the growth of the sunflower.Under the same pipe spacing,the sunflower growth indexes were better with the irrigation quota increasing.under the same irrigation quota,the sunflower growth indexes in the area of 30m spacing were better than that of 45m pipe spacing.The sunflower yield reached 5.0t.hm-2 under the treatment of 30m pipe spacing and 70mm irrigation quota,which was better than other treatments.Therefore,the treatment of 30m pipe spacing and 70mm irrigation quota was an appropriate irrigation and drainage mode in the test area. |
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