Effects Of Subsurface Drainage On Desalination In The Farm Of The Yellow River Delta

As a big agricultural country, total demand for grain sustained increases in recent years in china, improving saline soil has become an efficient way to expand agricultural acreage and increase grain yield. The experiment was carried out in the Xiaokaihe Yellow River Irrigation Authority of Bin-Zhou City from April 2012 to June 2013.There are five treatment, i.e., the drain space of subsurface pipe which the material is PVC were 30m、45m、80m separately, another treatment with the drainage material of straw is 50 m, the laid depth of all treatments was 2.5m, to study the improvement effects of subsurface drainage on coastal saline soils. The main results indicated that:(1)The variation of soil salinity in 0-20cm、0-60cm、0-100 cm in these four treatments appears consistency obviously: salt accumulation in spring、autumn,desalination in rainy season, salinity relatively stable in winter. The desalinization ratio of 0-20 cm profile is the highest, 0-100 cm profile is the lowest.(2) Subsurface pipe drainage can reduce soil salinity obviously. There is no significant difference on desalinization ratio of soil profile in four plots: soil desalinization ratio in 0-30 cm is variant; soil desalinization ratio in 30-100 cm decreased with soil depth. The soil desalinization ratio of plots from high to low in 30-60 cm is P45、 C50、P30、P80; in 60-100 cm is C50、P45、P30、P80.The effect of soil desalination of straw drainage plot will better than PVC drainage plots gone with the time.The best space in yellow river delta with high desalinzation is 45-50 m.(3) The correlation coefficient of P30 、 P45 、 P80 、 C50 between water level and rainfall were 0.545 、 0.525 、 0.513 、 0.525 respectively and significant correlation. The correlation coefficient between water level and evaporation were 0.416、0.478、0.377、0.494 respectively and significant correlation. The correlation coefficient between water level and drainage were 0.872、0.908、0.622、0.977 respectively and significant correlation. The correlation coefficient between water level and irrigation were 0.824、0.883、0.697、0.832 respectively and non-significant correlation. Evaporation can cause water level acutely vary, rainfall is the main factor to influence water level without other supplement water. Drainage can reduce the level effectively. Reasonable irrigation system can keep from secondary salinization caused by water level rising. Straw and PVC subsurface pipes can control water level by drainage.(4)Shallow groundwater salinity of C50、P45、P30、P80 declined 46.26%、38.22%、31.68%、24.26% respectively; Drainage water salinity in unit area is 78.52g、53.53g、24.17 g 、 31.34 g. Drainage discharge in unit area 0.0128m3、 0.0147m3、 0.0075m3、0.0063m3. Drainage water salinity of straw drainage is better than PVC drainage, but discharge of that is lower than PVC drainage with the same diameter and space.(5)Subsurface pipe drainage can effectively reduce the soil bulk density, increase organic matter soil total phosphorus and available nutrient; but reduce soil total nitrogen. And available nutrients increments of surface soil are greater than those of plough layer. But soil organic matter and deep soil available nutrient will be lost along with the time, we must pay attention to the late soil fertilizer management.(6) Crop yield increase obviously in 2012 and 2013 contrast with that in 2011. Drainage can enhance production and improve land productivity. Considering drainage and desalination under the local actual situation, we determine the suitable subsurface pipe drainage layout in clay saline-alkali soil of the Yellow River delta are: straw drainage with 50 m space、315mm diameter and PVC drainage with 45 m space、315mm diameter.