Effects Of Moistube Depths And Density On Tomato Growth And Soil Water-salt Transport In Solar Greenhouse

Tomato is one of the solanaceae family vegetables and loved by people for its fruit nutritious and unique flavor.It is one of the widely cultivated vegetables in solar greenhouse in the north of China.The secondary salinization of soil is the most prominent problem in the solar greenhouse,which seriously restricts the sustainable development of the modern agricultural land productivity.Moistube-irrigation is a new underground irrigation technology in recent years,whose core material is a semi-permeable membrane and providing water to the crop root zone soil in a slow and continuous flow direction.This new irrigation technology has the advantages of energy saving,low operating cost,easy operation,good anti clogging performance,less deep leakage and so on.After the water passed through the mistube,it formed an approximate cylindrical wetted zone in the soil to the pipe axis as the center.With the extension of the water time,the wetted zone expands continuously,based on the theory of ‘the salt moving with the water',the salt content of plant root zone could be continuously reduced.Meanwhile,it could create a suitable environment for crop growth,to achieve the effect of saving water and desalting salt.However,it is possible that the soil salt in the upper part of the mistube can be accumulated under the evaporation.In order,drip irrigation with mulch?CK?was used as a control group to explore the suitable technical parameters of moistube irrigation in solar greenhouse.Three kinds of depths?10,20,30 cm?and three densities?one,two and three moistubes with two lines of tomatoes in one planting ridge,respectively expresses as 1 tube with 2 lines,2 tube with 2 lines,3 tube with 2 lines?were set up to study on the effect of different depths and density of moistube on the tomato growth and soil water-salt transport in solar greenhouse.The experiment was done 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.The main research conclusions are as follows:?1?Moistube irrigation enhanced the growth and development of tomato fruit and root compared with the drip irrigation with mulch.Compared with control,moistube irrigation increased fruit diameter,weight,volume,total yield and irrigation water use efficiency,by 8.58%,11.99%,18.79%,60.93% and 103.40%,respectively.Our results suggested that water-saving under moistube irrigation conditions was as high as 37.73%.For tomato quality,the contents of vitamin C,soluble sugar and sugar-acid ratio also increased under moistube irrigation.Tomato total root length,total root surface area,total root volume,average root diameter and root dry weight were significantly increased respectively by 11.25%,5.47%,9.45%,11.72% and 8.10% in average.?2?The total root length of tomato was determined by the fine root length of 0<d<1mm?the proportion of total root length was 80.82%⁸7.54%?and the main tomato root length density was distributed in 0³0cm soil layer?the proportion of the total soil root length density was 74.92%⁸6.70%?.The root length density of different treatments decreased exponentially with the soil depth,their peak values were both in the 0¹0cm soil layer.?3?The plant height,fruit shape,yield of per plant and total yield of tomato were the highest under the condition of 10 cm depth and 3 tubes with 2 lines.Depth 10 cm and 1 tubes with 2 lines could get the highest irrigation water use efficiency,while when depth 30 cm the vitamin C,soluble sugar and sugar acid ratio were the largest,and the comprehensive quality ranking first.It concluded that depth 10 cm and 2 tubes with 2 lines were most suitable for the growth of tomato roots,which tomato total root length?3570.22 cm?,root length of diameter less than 1 mm?3032.19 cm?,total root surface area?765.07 cm2?and root dry weight?5.71 g?were the largest,meanwhile root comprehensive evaluation ranking first under this conditions of the experiment.?4?The soil salt content in solar greenhouse was significantly higher than that in open field,the average salt content of the cultivated layer?0²0cm?reached 2.745g·kg^-1,which was close to the critical point(2.75g·kg^-1)of crop growth.It can be seen that mild soil salinization had been occurred in solar greenhouse soil.?5?Compared with the CK treatment,moistube irrigation had a high degree of desalination,the average relative desalinization rate of 0⁶0cm soil layer was increased by 32.49% and the main root zone?0⁶0cm?was 76.30% higher than that of CK.The soil water content and relative desalting rate increased with the increase of mistube density.A high water and low salinity zone was formed in the soil layer of the moisture buried depth,when buried depth were 10 cm and 30 cm,the main root zone?0³0cm?and the minor root zone?30⁶0cm?reached the highest soil water content,the lowest salt content and the highest relative desalination rate respectively.It was beneficial to the soil salt leaching in the main root zone under shallow buried conditions,and in the minor root zone under deep conditions.The soil salt content was increased at the late growth stage of tomato by 30 cm buried depth and 1 tubes with 2 lines,it could exacerbate soil secondary salinization.In summary,shallow buried moistube tube was suitable for tomato growth.It could be recommended as the best technical parameter combination for moistube irrigation in solar greenhouse in Yangling Shaanxi,which can obtain better yield and quality of tomato,but also can avoid the accumulation of salt in the surface soil,reduce the risk of secondary salinization,and this method can also reduce the workload of trenching-burying moistube in field operation at the same time.For mild secondary salinization soil,the method of shallow buried and sparse moistube were suggested to used,which can ensure the yield(87.38 t·hm^-2)were not significantly reduced,made the irrigation water use efficiency?108.91 kg·m-3?and the water saving rate?67.31%?were the highest,and the pipeline investment cost is greatly reduced under the condition of 10 cm depth and 1 tubes with 2 lines in this experiment.For severe secondary salinization soil,we suggested that the method of shallow buried and dense moisture can be better used to control the occurrence of secondary salinization in tomato root zone.Although this experiment was carried out in the mild secondary salinization soil,the results can provide a reference for severe secondary salinization soil.Our results indicated that 10 cm depth and 3 tubes with 2 lines were the best for reducing the salt content of soil,whose average relative desalinization rate of 0⁶0cm soil layer was 22.27%,in tomato main root zone?0³0cm?the relative desalinization rate was 29.86%.