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China Agricultural University (2014)

Salt Movement Trends in Cotton Fields with Long-term Drip Irrigation under Mulch in Typical Oasis and Irrigation Management

王振华; WangZhenHua

Titre : Salt Movement Trends in Cotton Fields with Long-term Drip Irrigation under Mulch in Typical Oasis and Irrigation Management

Auteur : 王振华; WangZhenHua

Grade : Doctoral Dissertation 2014

Université : China Agricultural University

Résumé partiel
Drip irrigation under mulch has been widely practiced in the arid region of Northwest China especially the saline-alkali soils in Xinjiang. As, theoretically, drip irrigation under mulch only affects salt distribution in root zones and salts are not drained out of the soil baby, whether salts will accumulate in root zones with long-term drip irrigation under mulch is an important question deciding whether such an irrigation method can be sustainably applied in arid regions. Previous results have provided a lot on water and salt management for drip irrigation under mulch but little on the actual changing trends of salts in fields with long-term drip irrigation under mulch. Therefore, in this study, salt changes in five agricultural fields with2-16years of drip irrigation under mulch were monitored consecutively from2009-2013. These fields were located in Regiment121, Shihezi, Xinjiang, which is a typical oasis. Study area wasteland0~40cm soil salinity average25~70g/kg, groundwater depth2-4m, sandy loam soil with varying degrees of salinization mainly in cotton irrigation quota on average816.15mm, irrigation water salinity0.4g/L or so.The results revealed soil salt content evolution trends in agricultural fields with long-term drip irrigation under mulch under current irrigation regime. Corresponding irrigation management strategies were proposed. The results from this study are expected to provide theoretical basis for the sustainable application of drip irrigation under mulch in arid regions. And main conclusions were drawn as follows :(1) Water and salt distribution and changing characteristics in cotton fields with long-term drip irrigation under mulchDrip irrigation under mulch has significantly influenced and changed water and salt distribution in farmlands under natural conditions. Under current irrigation regime, for the0-140cm soil layer, soil moisture was high in fields with long-term drip irrigation under mulch. Soil moisture was high after irrigation for the whole field, inside the films, between the films, or for the different growth stages of cotton. And there were no significant differences in soil moisture between positions and times. In addition, interannual variation was small. Distribution and variation of soil moisture and salt to a depth of300cm or to the water table in cotton fields with drip irrigation under mulch were influenced by irrigation, crop water assumption and evaporation together. Soil salt content and distribution displayed fairly big spatial and temporal variation with application years of drip irrigation under mulch. Holistically, high salt contents with great variation were found between films in the horizontal direction. Salt contents within films were low especially in the0-100cm layer, which was suitable for cotton growth. In the vertical direction, great variation in salt content was found in the surface soil layer while the deeper the layer, the smaller the variation, and the smaller the differences in salt content between different horizontal positions with gradual decrease as a whole. Soil salt content as a whole exhibited decreasing trends during the whole cotton growing period within the year especially after the irrigation in cotton seedling stage in April. With longer years of drip irrigation under mulch, interannual salt content variation coefficient and difference decreased gradually.(2) Soil salt content evolution trends in cotton fields with drip irrigation under mulchUnder current irrigation regime, drip irrigation history had significant impacts on the distribution of soil salt content in the0-300cm soil layer. After a single irrigation, soil salts in cotton fields with drip irrigation under mulch displayed pronounced movements in both the horizontal and vertical directions. Soil moisture was the main factor affecting soil salt movement in cotton fields with significant convection in soil salt movement. After several times of irrigation, soil salts showed a holistic downward movement which was close to a one-dimensional movement. As a whole, average salt content displayed the same first-rapidly-then-slowly decreasing trend as a power function exhibits with longer drip irrigation history. The first3years of drip irrigation was the rapid desalinization stage when soil salt content decreased rapidly compared with those in surrounding uncultivated lands.

Mots clés : long-term drip irrigation under much; soil salt movement; cotton field; irrigation management; irrigation regime;

Présentation (CNKI)

Page publiée le 5 septembre 2014, mise à jour le 24 septembre 2017