Study On Drip Irrigation Water-Saving Mechanism And Irrigation System Pattern Of Gobi Grape

The Hexi Corridor of Gansu lies in inland arid regions of northwest China, withan extremely dry climate, a very low precipitation and so high an evapotraspiration.However, it has abundant resources of light and heat, also to be one of the highquality grape producing areas of China. It is widely accepted that the issues such aswater shortage, overexploitation of underground water as well as agricultural wateruse severely waste to be faced with in Hexi Corridor of Gansu, which has resulted in aseries of problems like the sandy vegetation's wither and death, the rampagingsandstorms, soil salinization and the serious contradictions between agricultural wateruse and ecological water use. Undoubtedly, the development scale of grapes isrestricted significantly. In view of this, seeking an efficient water-saving irrigationmode suitable for grapes of Hexi Corridor seems to be so urgent, which has animportant meaning for the local economy, ecology as well as social benefits.The mode of drip irrigation under mulch is considered as an efficientwater-saving irrigation mode that could promote a localized irrigation in crop root,and where always be kept wet, it has a great application potential in Gobi arid areas.However, the research on drip irrigation of grapes in Gobi arid regions of HexiCorridor is not enough in-depth, and a widely existing phenomena of more irrigation,less irrigation and not timely irrigation in this region, also because it takes much timeand labour in large-area film mulching to the drip irrigation of grapes, as well as theincreasing production cost, resulting in a less attention to water-saving and benefitincreasing of drip irrigation in Gobi arid regions. Aiming at the problems, thisresearch, therefore, based on the existed literature, was conducted on grape dripirrigation under mulch in Zixuan grape plantation of Jiayuguan of Hexi Corridor ofGansu in2010and2011, included the dynamic variation characteristics of soilmoisture for grape drip irrigation under mulch, the changes of soil water contentimpact on crop's ecology, physiology and biochemistry, as well as on grape yield,quality and water use efficiency(WUE), also on its economic efficiency. The results as follows:(1) The dynamic variation characteristics of soil moisture under different dripirrgation treatments with80cm sand soil layer in depth of0⁸0cm for wine grape"cabernet sauvignon" and with20cm gravel soil layer in depth of0⁴0cm for winegrape "Merlot Noir" show that, the soil water content of "cabernet sauvignon"and"Merlot Noir" is both higher than that of the conventional drip irrigation(CDI) inno mulch treatment(CK). And the plastic cover treatment of T₁and T₂respectively hasa water saving amount of33%and17%compared with the CDI in no mulch, and thetreatment of T4has an irrigation amount of multiple-output60mm per mu. The resultsfurther show that, in the growth period of grapes, the water consumption from high tolow is respectively the berry growth period, berry maturity period, shoot-growingstage and florescence. We also find out the optimal irrigation amount of "cabernetsauvignon" and "Merlot Noir" is160m³(T₁) in their growth periods, and the irrigationquota is10～20m³/mu.(2) The analysis on the effects of different drip irrigation amounts on the diurnalvariation of photosynthetic characteristic of wine grape, it indicates that the curve ofnet photosynthetic rate of Gobi grape shows the tendency of single slope line from am8:00to pm16:00. The daily mean leaf WUE of "cabernet sauvignon" with thetreatment of film mulch and less irrigation amount(T₁) is0.13mmolCO₂·mol^-1HO₂,0.19mmolCO₂·mol^-1HO₂and0.15mmolCO₂·mol^-1HO₂higher than that of the otherfilm mulch treatments T₂-4, also is0.11mmolCO₂·mol^-1HO₂higher than that of theCDI in no mulch treatment(CK). Similarily, The daily mean leaf WUE of "MerlotNoir" with the treatment of T₁is0.23mmolCO₂·mol^-1HO₂,0.3mmolCO₂·mol^-1HO₂and0.23mmolCO₂·mol^-1HO₂higher than that of the other film mulch treatments T₂-4,likewise0.32mmolCO₂·mol^-1HO₂higher than that of the CDI in no mulchtreatment(CK). And the test on photosynthetic characteristics of wine grape in Julyand Augest of2011further demonstrates that the leaf WUE with the treatment of T₁and in no mulch treatment(CK) is also higher than that of the other film mulchtreatments, the treatment of T₁is nevertheless has a water saving amount of33% compared to the CDI in no mulch treatment(CK), it is no doubt that the treatment ofT₁is efficient to water saving and improve the leaf WUE.We also find out the highcorrelation between the soil water content and each photosynthetic parameter.(3) The changes of leaf chlorophyll content for wine grape "cabernetsauvignon" and "Merlot Noir" show that, each treatment under different drip irrgationin2010and2011, the leaf chlorophyll content with plastic cover treatment is higherthan that of the CDI in no mulch treatment under the same irrigation amount. The leafchlorophyll content with the treatment of T₁and the CDI in no mulch treatment(CK)is both low, the treatment of T₁and CK do not hinder the normal growth of grape, butthe treatment of T₁reach the saving water amount of120mm per mu compared withthe treatment of (CK). Also, there is the significant positive correlation between thechlorophyll content and soil water content. Moreover, the tests on physiological andbiochemical characteristics for "cabernet sauvignon" and "Merlot Noir" of2010and2011show that, the index values of physiological and biochemical as well as thegrowth index with plastic cover treatment are superior to that of the CDI in no mulchtreatment, and the value under plastic cover treatment with more irrigation amount isalso better than that of the treatment with less irrigation amount, the treatment of T₁could save water180mm per mu compared with the treatment of T4. No doubt that thetreatment of T₁could well deal with the problem of water shortage in Gobi airdregions of northwest China.(4) The results of fields experiment further indicate that, the drip irrigation of T₁with240mm could achieve the water saving amount of120mm per mu, which istherefore considered as an optimal irrigation amount that make the yield and qualityof grape simultaneously improve, and the grape yield under this mode is higher thanthat of CDI in no mulch treatment. The annual yield of "cabernet sauvignon" and"Merlot Noir" in2010and2011with the treatment of T₁enhanced by2485.65kg/hm²and2009.78kg/hm²in comparion of the CDI in no mulch treatment (CK). At thesame time, the drip irrigation under mulch improves the quality of grape. Further, it isfound that water is considered as one of the important factors that influencs the yield and quality of grape.(5) The simulation results on the correlations of irrigation amount, grape yieldand WUE show that, irrigating amount and WUE are the two key factors to influencegrape yield, the WUE is especially important to grape yield. Likewise, the treatmentof drip irrigation under mulch could significantly improve the WUE of grape, theannual mean WUE of "cabernet sauvignon" and "Merlot Noir" with the film mulchtreatment of T₁is1.51kg.mm^-1.hm^-2and1.16kg.mm^-1.hm^-2higher than that of theCDI in no mulch treatment (CK). The water economic efficiency of film mulch isoverall higher than that of the CDI in no mulch treatment (CK), and the annual watereconomic efficiency "cabernet sauvignon" and "Merlot Noir" in2010and2011withthe treatment of T₁seperately increased by3.34yuan.mm^-1hm^-2and1.99yuan.mm^-1hm^-2in comparion of the CDI in no mulch treatment (CK). The film mulchtreatment of T₁is more helpful to improve water economic efficiency with a lowercost investment. The impacts of productive factors input on grape yield reveal thatwater has a significant effect on grape yield. So, the mode of drip irrigation undermulch has an enormous water-saving potentiality in arid desert regions, and particularkey to develop the plant of grape in this region. A reasonable irrigatied systemsiutable for drip irrigation under mulch of arid desert regions is finally put forward.