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China University (2013)

Research On Prediction And Simulation Of Water And Salt Transport Under Drip Irrigation With Mulch In Arid Regional

Dan Y Y

Titre : Research On Prediction And Simulation Of Water And Salt Transport Under Drip Irrigation With Mulch In Arid Regional

Auteur : Dan Y Y

Grade : Doctoral Dissertation 2013

Université : China University

Freshwater scarcity and soil salinity increases are frustrating the sustainable developmentof agriculture worldwide, particularly in arid and semi-arid regions. Xinjiang in northwestChina is typical of arid and semi-arid region which is serious affected by two factors. Toaddress the problems, some measures have been applied. Drip irrigation is considered asone of the best methods which can increase crop yields ; reduced water application ;decreased salinity ; and deep percolation. Under drip irrigation, confluence occurs betweenpairs of emitters and the area of confluence is termed the ’overlap zone’, as well as plants(e.g., cotton) are always grown in the overlap zone between neighboring emitters in a field,hence knowledge of salinity distributions in the zone is very important for achieving highcrop yields. Salinity increases with times under drip irrigation, it is very important tounderstand salt accumulation. In order to understanding water and salinity transport withdrip irrigation, we analysis the problem by combination experiments with simulations. Theconclusions as follows:1. Research on wetting front dimension with different emitter discharge,different irrigationvolume,different emitter spacing, using the model developed by Schwartzman and Zur(1986) as a starting point and developed a new empirical model for wetting frontdimension with double-point-source drip irrigation. The following relationship:where W and W1denote the widths of the wetting fronts below the dripper and in theoverlap zone, respectively.2. HYDRUS3-D can successfully simulate both temporal and spatial soil water contentdistributions, as well as the salinity distributions with double-point-source drip irrigation under field conditions. Additional simulations with HYDRUS-3D were used to evaluatethe effects of various design parameters on desalinization zone pattern around the overlapzone. The additional simulation results showed that the area of the desalination zone was :(1) positively correlated with irrigation volume, following a power function ;(2) positivelycorrelated with discharge rate, following an exponential function ;(3) the simulation resultsalso showed that, for the fine soil type, the horizontal and vertical distances were nearlyuniform, for the coarser soil type, the extent of diatance was far greater vertically than itwas horizontally, as well as desalination also follows.3. Employed the HYDRUS-3D to determining optimal drip irrigation volumes with theHYDRUS-3D model for cotton established by dry seeding and planting afterpre-germination under mulch and confirmed by cotton emergency.4. The lower salt content in high frequency irrigation during the growth period. Therelationship between the frequency winter irrigation and soil salt content has a positiverelation.5. Compared between observed and simulated, the result showed that the SaltModel canaccuracy predict salt accumulate for the regional.6. Based on the simulation results, we determined the suitable irrigation schedule including:irrigation water mineralization1g/L,irrigation volume4500m3/ha in growth periods,winter irrigation3000m3/ha,water table level is1.8m. Predict attained the water-saltbalance in9year under the irrigation schedule.

Mots clés : water and solute transport, drip irrigation with mulch, HYDRUS-3D software, SaltModel software

Présentation (Globethesis)

Page publiée le 21 avril 2013, mise à jour le 10 janvier 2018