Study On Soil Water Salt And Fertilizer Migration Rule And Root Regulation In Indirect Subsurface Drip Irrigation Of Jujube Tree In Southern Xinjiang

The characteristic forest fruit industry is the pillar industry in southern Xinjiang,but the shortage of water resources,the serious secondary salinization of the soil and the low utilization rate of agricultural and fertilizer resources have become the main factors that restrict the development of the southern Xinjiang.At present,surface drip irrigation is widely used in the irrigation mode of fruit trees in southern Xinjiang,but surface drip irrigation can easily lead to the enrichment of fruit tree roots to the surface wetting area,resulting in the shallow distribution of root system and the drought resistance.At the same time,the relatively low utilization rate of water and fertilizer further restricts the increase of fruit tree yield and quality.It is of great significance and practical value to improve the existing water-saving irrigation technology and establish a irrigation mode suitable for local fruit trees to save water,fertilizer,fertilizer and salt.In the paper,taking the dwarf and densely planted jujube as the research object,using the indirect underground drip irrigation technique,through the laboratory test and the 5 year(2012-2016 years)long-term location experiment,the depth of the buried water seeding device(irrigation depth),the diameter of the water guide device,the amount of irrigation and the fertilization under the condition of indirect drip irrigation are studied by the quantitative and qualitative analysis method.The effects of irrigation and Fertilization on the temporal and spatial changes of soil water,salt and fertilizer in the growth period of the dwarf red jujube and the control effect on the root system of jujube trees were studied.The main irrigation technical parameters suitable for indirect drip irrigation in southern Xinjiang were preliminarily explored.The main conclusions were as follows:(1)Under the indoor conditions,when the depth of the water guide is 25cm,the soil water content in the 20-30cm soil layer of the outlet is the highest.With the increase of the distance between the outlet and the outlet,the water content in each soil layer in the vertical direction is gradually reduced in two directions.The nearer to the wetting body,the nearer the outlet of the outlet,the lower the salt content of the soil,with the outlet of the water outlet.With the increase of vertical and horizontal distance,soil salinity also increased.The drop head flow has a significant effect on the migration and distribution of water and salt in humid body.Large flow is beneficial to the movement and leaching of water and salt in the horizontal direction,while the small flow is beneficial to the movement and leaching of water and salt in the vertical direction.After infiltration,the soil NO3--N is mainly distributed within the 10-40cm soil layer below the surface of the earth.With the increase of the concentration of the fertilizer,the distance of NO3--N outward diffusion of soil increases.(2)Under the experimental conditions,increasing the amount of irrigation will increase the depth of the downward movement of water and increase the water content of the main root zone.After single irrigation,the desalination rate increases with the increase of the amount of water when the diameter of the water guide is fixed in the 10-40cm soil layer of the root zone of the jujube tree.When the amount of water is fixed,the desalination rate decreases with the increase of the diameter of the water guide device.In this layer,the soil desalination rate was higher under the combination of smaller diameter of water guide device(D = 50 mm,75 mm)and larger irrigation volume(W = 17-19 L·tree-1).In consideration of many factors such as high quality,high yield,water saving and salt control,the parameters of indirect drip irrigation are as follows:the diameter of the water guide device and the amount of water are controlled around 75 mm and 17-19 L,and the flow rate is 3 L·h-1.Under the combined model,the average desalination rate of the 0-50cm soil layer and the distance from the distance to the water guide is 25.2%,the average yield of the red date is 2579 kg·hm-2,the water use efficiency is 3.48 kg·m-3,and the same irrigation amount is 16.7%more than that of SDI.(3)In the plot experiment of the control of the root system of jujube tree,with the increase of irrigation depth and fertilization,the root length of the surface was relatively reduced with the increase of the depth of irrigation.The root length density of the deep root system increased relatively.The fine root distribution basically showed the trend of "wide shallow type" to "deep root";with the increase of fertilization,the fine roots of the 0-60 cm soil layer(0 mm<d<2 mm)The root length density and the root length of the root(2 mm<d<5 mm)decreased gradually.The length of the root length of the fine root of the jujube tree showed a vertical distribution characteristic of bimodal pattern,and the peak appeared in the 10-20 cm soil layer and the 80-90 cm soil layer.(4)In the plot experiment of the influence of irrigation depth,irrigation amount and water fertilizer coupling on water and nutrient and yield and quality of the root area of jujube,the content of available nitrogen,available phosphorus and available potassium in the soil sections of root region gradually decreased with the increase of soil depth during the growth period.But it was influenced greatly by different amount of fertilizer and depth of irrigation(depth of water guide device).When the depth of irrigation was small,the content of available nitrogen and available phosphorus in 0-20 cm soil layer changed violently with the increase of fertilizer amount,and the content of soil nutrients in other soil layers changed relatively slowly,with the increase of irrigation depth.In addition,the concentrations of available nitrogen,available phosphorus and available potassium in soil 0-20cm soil tended to be slow when the amount of fertilizer was increased,and the content of available nitrogen,available phosphorus and available potassium in the 20-40 cm and 40-60 cm soil layers was increased effectively.With the same irrigation depth,with the increase of fertilization,the yield of red dates increased basically.The content of Vc,protein and reductive sugar in the fruit of the red jujube showed an increasing trend,and the organic acid showed a tendency to decrease gradually.At the same time,with the increase of the depth of irrigation,the yield showed a trend of increasing and then decreasing.The organic acid shows a trend of gradual decrease.In consideration of the efficient utilization of water and fertilizer,salt control,high quality and high yield and rational distribution of root system,the diameter of the water guiding device is 75 mm,the depth of the water guiding device is 27-35 cm,the irrigation quota is 70 m3·hm-2,and the fertilization amount is 118-150 kg·hm-2.