Study On The Moist Soil Of Surge Root Irrigation For Jujube In The Loess Hilly Region In Northern Shaanxi

There coexist in the loess plateau region soil and water loss and drought and water shortage, which seriously affects the development of local agricultural production. Jujube as an important industry in the hilly and gully region of southern yulin, faces backward irrigation techniques and low economic benefits, which is caused by drought and water shortage.Surge root irrigation is a novel irrigation technique invented by National Engineering Research Center for Water Saving Irrigation, at Yangling, Northwest A&F University. Underground partial irrigation was carried out by directly transporting water and fertilizer to root zone through microtubules, which created the suitable conditions of water, fertilizer, air and heat in the crop root zone. Therefore, the effects of saving water, increasing yield,saving labourand improving efficiency and quality are achieved, the surface operation was not affected, the soil physical and chemical properties were improved, crop diseases and soil water evaporation were reduced, the water flow transition protector was prevented from blocking. Surge root irrigation was first applied at the mountain micro-irrigation demonstration base for jujube at Mengcha village, Mizhi county, Shaanxi province. This technique is especially suitable to fruit trees and afforestation irrigation on the slope with greater topographic relief, increases the regional water utilization rate and utilization efficiency,promotes the local advantage industry-jujube production, and increases the ecological and economic benefits of economic forest (mountain jujube and so on).The study on soil wetted volume characteristics under Surge root irrigation is helpful to the correct system design and field crop water management of high level. To seek the soil wetted volume shape change and soil water distribution and migration law during the irrigation process and after irrigation under Surge root irrigation, the surge root irrigation infiltration experiment was carried out by use of field undisturbed soil in the mountain jujube forest.Under Surge root irrigation and under the conditions of different apertures, hole depths and flows, the wetting front migration of soil wetted volume and water distribution laws were studied, which found out that the horizontal diffusion radius, upward infiltration distance and downward infiltration depth all increased as the infiltration time increased, which accords with the power function relationship, and infiltration rate gradually decreased as infiltration time increased. Under the condition of small aperture, the upward infiltration rate was faster than that under the condition of big aperture, while the horizontal diffusion rate and downward infiltration rate were faster under the latter condition. Under the condition of big aperture, soil water diffused more uniformly in different direction, which was embodied by the fact that the moisture content contour and wetting front migration curve shape of soil wetted volume were proximal to circular. As the hole depth increased, the upward infiltration rate increased, and the horizontal diffusion rate and the downward infiltration rate decreased, and the soil wetting region downward shifted synchronously. As for the zone with high soil water content(soil water content≥24%), it had an upward displacement as the seeper depth increased, the zone decreased continuously in the horizontal and vertical downward directions; soil moisture curve shape was similar to wetting front migration curve shape, which changed from well-distributed circular to flat and long shape of uneven distribution.As the flow increased, the horizontal diffusion radius, upward infiltration distance and downward infiltration depth of soil wetting volume increased accordingly and the upward infiltration distance increased the most and the seeper depth affected the upward migration distance of wetting front very significantly; as the flow increased, the soil wetted perimeter became bigger, and the range of the zone with high water content at the the bottom of hole (soil water content≥24%) expanded. When flow was less, compared with larger flow, zone with high water content formedaround the hole bottom not only had a small range and but also its internal average moisture content was low. Small flow irrigation can make water diffuse more uniformly; within 24h, after stoping water supply, during the soil water redistribution process,there was a greater motion and change; after stoping supplying water, within 48h, the soil water content was basically stable and the soil wetting front basically came to a steady state and did not extend any longer; the volume of soil wetting volume was affected by irrigation amount and flow; under the conditions of different flows, there all existed a very significant power function relationship between the volume of wetting volume and irrigation amount and between irrigation amount and wetting volume horizontal diffusion radius and vertical diffusion distance; according to the root distribution characteristics of the perennial jujube of five years, the suitable irrigation time and irrigation amount was determined; and there was a recommendation that the suitable hole depth range is 30~40cm, the aperture isφ6cm, and the flow range is 4~10 L/h for bubble root irrigation. To find out the irrigation effect under single point source and multi point sources irrigation of bubble root irrigation, the study on soil wetted volume under double point sources irrigation was carried out. The wetting front migration velocity at the intersection surface was faster than that at the hole. The vertical upward and vertical downward wetting distance at wetting front intersection surface and the vertical upward and vertical downward wetting distance at the hole were closer and closer to each other. The shape of wetting front in the horizontal direction was closer and closer to a horizontal line, and that is, finally the profile shape of wetting soil under interference infiltration in the direction of hole arrangement would nearly become a ribbon. In the middle area around the hole bottom, the soil water content contour distribution was relatively complicated and the contour distribution was similar to the"saddle"on the topography. A comprehensive comparison of wetting volume uniformity under different point sources number and an analysis of water data under single and double point sources irrigation were made, and therefore the conclusion can be drawn that the double point sources irrigation got the best irrigation effect, the single point source irrigation took second place, and the four point sources irrigation had a poor effect.In this paper the bubble root irrigation technique was proposed. The application of this technique can not only reduce mountain irrigation system cost, and but also it can achieve the dual target of saving water and increasing yield. So bubble root irrigation has a very wide application prospect on the loess plateau of drought and water shortage.