Study On Characteristics Of Wetting Body Under Linear Source Drip Irrigation On Loessal Soil With Ridge Culture In North Of Shaanxi

Potato takes the most important place of crop planting in Yulin region Shaanxi province. Therefore, improving the quality and quantity of potato is so necessary to develop the local featured industry of Yulin region. However, it is limited by drought and low water use efficiency. According to this situation, drip irrigation is introduced in potato planting with the support of science & technology bureau of Yulin city.Drip irrigation is a kind of modern water conservation technology, which can saving water and help crops get high quantity and quality with reasonable irrigation system design and water management of high level, and the study of wetting body under drip irrigation, which is a link to connect irrigation system and crop roots, is the precondition of reasonable system design and water management of high level. As for crops which are planted in row and with little planting spacing just like potatoes, the wetting body under drip irrigation for which would confluent as a humid zone along the drip irrigation pipe, which is called linear source drip irrigation. To help determine the appropriate dripper discharge and irrigation amount which can provide a reliable theoretical basis for the drip irrigation system design for potato in Yulin region , a series of outdoor experiments about linear source drip irrigation on loessal soil with ridge culture were conducted in Mengcha experiment base in Mizhi, focusing on the wetting sharp ,transport law of wetted front ,the distribution of soil moisture in wetting body and the course of soil water redistribution under different irrigation amount, dripper discharge and initial soil water content, and the conclusions got as follows :(1)Under linear source Interference Infiltration conditions, the vertical infiltration distance and transport speed of soil wetted front have good power functional relation with infiltration time on the intersection surface and the side under drip emitter. Based on analysis of the relationship between fitting parameters of equation and dripper discharge, an empirical model was found to predict the characteristics of wetting body under different dripper discharge. According to which, also the distribution of potato root, irrigation amount of a single emitter can be determined in the precondition of non deep percolation.(2) Under the experimental conditions, the contour map of soil water content ,on the profile along the drip irrigation pipe, showed as a series ellipses centered roughly on the drip emitter above the soil layer between 10cm-15cm depth ,while under 15cm soil layer the contour map became flat. Soil water content in the vertical direction of emitter has parabola functional relation with wetted depth. In the situation of the same irrigation volume, the dripper discharge has little influence on the average soil water content of the wetting body.(3) As the characteristics value of the wetting body vary greatly in the process of re-distribution of soil water , especially within 24h after drip irrigation stopped, and the change rate decreases rapidly after drip irrigation stopped for 24h.Therefore, the characteristic values of wetting pattern when 24 hours after the end of the drip irrigation is relatively stable ,they can be used as the basis of irrigation volume for linear drip irrigation system design.(4) For the test soil, the uniformity of soil moisture along the drip irrigation pipe can be increased by increasing dripper discharge and irrigation amount, but subject to restrictions of ridge size, also in order to prevent run-off along the slope, the effort is not obviously.(5) The experimental results show that: according to the distribution of soil water needed by potato, while dripper spacing is 30cm, the proper depth of planned wetting zone for drip irrigation system design is 40cm, dripper discharge is 2L / h,the irrigation time is 7h..