Optimized Regulated Deficit Irrigation Mode And Crop Coefficient Of Drip Irrigation Jujube In Loess Plateau

The condition of the Loess Plateau is special: the ecological environment is fragile, thesoil is eroded seriously and the production technology of the main specific fruit is backward.Considering that special condition, this research is to ensure the sustainable utilization ofwater resources in the Loess Plateau region, improve the economic benefit of people whohave returned farmland to forest, meet the agricultural modernization and improve theregionally ecological environment conditions; additionally, the research object is the specificfruit—jujubes—in the loess plateau region. In the different growth periods of jujubes, theresearch designs different water deficit treatments, which are based on the dynamic change ofsoil water. The research analyzes the affection of Regulated Deficit Irrigation (RDI) onjujube’s water need and consumption rule, physiological and ecological index, fruit qualityindex, yield and water use efficiency; additionally, the research establishes the entropytheory based on the comprehensive benefits model of jujubes under RDI and the estimationmethod of jujube orchard soil moisture’s FAO-56water stress coefficient, and establishes thejujube’s RDI system under drip irrigation in Loess Plateau region. The result of this researchgains the jujube’s optimal irrigation model and crop coefficient under drip irrigation in theLoess Plateau, which provides a theoretical basis for promoting sustainable jujubes withsaving-water, stable-yield, high-quality and efficient in the Loess Plateau.(1) According to the study of soil moisture distribution characteristics under differentirrigation conditions, it has been concluded that there is obvious difference between differentwater deficit treatments in the same growth period. The soil water consumption trend ofdifferent water deficit treatments is slower than CK. The same deficit degree in differentgrowth periods of soil moisture rate appears to be quite different: the soil moisture rates ofjujube’s flowering and fruit-setting period and sprout developing period are relatively higherthan in other growth periods.(2) The jujube’s crop coefficient under drip irrigation in the Loess Plateau is sequencedfrom large to small as follows: fruit developing period> fruit maturing period> flowering andfruit-setting period> sprout-developing period; additionally, there are two curves relationshipbetween crop coefficient and leaf area index. As the RDI treatments in water deficit growth period, crop coefficients are generally lower than CK, that is, there is a water stress coefficient.The water stress coefficients in the water deficit periods under different RDI decreases aswater deficit degree increases, that is the severe RDI<<moderate RDI<light RDI.(3) According to the study of jujube’s ecological indexes, RDI has significant effect onthe growth of jujube’s various organs. New shoot length, leaf area index and the number offruit blossom are all under different effects of RDI. Considering the effect of RDI on jujube’snutrition growth and reproduction growth, moderate RDI in the sprout developing period cancontrol the redundant growth to suppress jujube’s new shoot growth and leaf area index, andincrease the number of blossom and fruit bearing number. Especially the moderate RDItreatment T2(M-P1) in the sprout developing period has a relatively active effect; however,the flowering and fruit-setting period doesn’t suit for water stress, which can decrease thenumber of blossom and fruit, thus affecting the jujube’s economic benefits(4) Jujube’s physiological index in Loess Plateau has significant difference in response towater deficit and rewatering. In the condition of water deficit, daily curves of netphotosynthetic rate under each RDI treatment generally lower than CK; additionally, thechanges of curves decreases as the RDI treatment increases, that is, severe RDI <moderateRDI<light RDI <CK. After RDI, the rewatering significantly increases the netphotosynthetic rate, and the peak time of net photosynthetic rate curve moves forward. Duringthe water deficit period, jujube leaf’s stomata conductance under RDI treatment generallydecreases; after rewatering, the stomata conductance increases. In the same weatherconditions, change of leaf water directly connects with RDI degree, that is, it decreases as thewater deficit degree increases.(5) RDI treated in different growth periods has effect on fruit physical quality index. Themoderate RDI and the severe RDI treated in the fruit developing period significantly decreasefruit weight and volume. RDI can decrease fruit’s water content, bad fruit rate, increase fruithardness. Specifically, the RDI treated in the fruit developing period most significantlydecreases fruit’s water content and increases fruit hardness, reaching9.1%and10.3%; thesevere RDI treated in the fruit developing period decreases the bad fruit rate mostsignificantly reaching20.1%. RDI treated in different growth periods has significant effect onfruit’s chemical quality index. Specifically, the severe RDI treated in the fruit maturing periodmost significantly decreases jujube’s organic acid content(P<0.05), the average decreasingrange is25.5%; that most significantly increases fruit’s vitamin C content, the averageincreasing range is23.9%. The moderate RDI treated in the flowering and fruit-setting periodmost significantly increases fruit’s soluble solids, the average increasing range is25.3%.However, the severe RDI treated in the fruit developing period most significantly decreases soluble protein, decreasing of14.8%in3years.(7) Applying comprehensive optimum seeking method on different RDI treatment andbasing on fuzzy evaluation method of information entropy to establish the evaluation modelof benefit under RDI treated in jujube in Loess Plateau area. According to the test data ofdifferent RDI treated in jujube’s different growth period during2011~2009in Loess Plateauregion, considering fruit’s physical index, chemical quality index, yield, water use efficiencyand economic benefits, this research provide comprehensive and objective evaluation of RDItreatment benefit.(8) Applying the calculated model of FAO-56water stress coefficient to simulate thedynamic process of soil moisture content under water stress of drip irrigation jujube’s in theLoess Plateau region, and additionally analyzing the precision changes and error reasons ofjujubes in different growth periods calculated by computer model.(9) Establishing the optimum RDI system of drip irrigation jujubes in Loess Plateau,referring the analysis of RDI’s influence on jujube’s each index, applying the treatment ofcomprehensive benefit maximization as the model, according to the following rule—applyingmoderate RDI in the sprout developing period, insuring adequate water supply in theflowering and fruit-setting period and fruit developing period, applying severe RDI in the fruitmaturing period—considering the precipitation conditions of different years and jujube’swater consumption tested, this research has designed the RDI system of drip irrigation jujubesin Loess Plateau region.