| The area of the arid and semi-arid regions accounts for about 52.5% of the total area of China, and the rainfall of the crop growth stages in most areas of the semi-arid region in Northwest is less than 250mm, which cannot meet the water demand for normal growing, so irrigation has a irreplaceable effect on the high and stable yield. The lower irrigation water use efficiency in the study area and irrational competitions for surface water between its upper and lower reaches have resulted in serious soil erosion, deteriorated ecosystem and serious conflict of water shortage for both agricultural and ecological water demand. However, this area is an important productive base of good quality fruit due to the abundant sunshine and large day/night temperature range. The pear-jujube which is the special local export fruit of this area and also one of the supporting industries should be mainly developed during the process of the planting structure adjustment. So, to use the limited water resources for efficient irrigation of these crops and to enhance irrigation water efficiency have become an important issue of this area.According to the scarce water resources the fruit industry in the semi-arid region of northwest are facing, this paper focuses on the characteristic economy fruit tree, pear-jujube tree, and developed on the experiments in the greenhouse and the oasis field respectively in Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University and in the pear-jujube orchard located in Chengguan Village, Dali Town, ShaanXi Provence. This paper has made systematic research about characteristics of soil water dynamic changes, water deficit of the root-zone of pear-jujube tree with regulated deficit irrigation, physiological control in the process of the water use and the stomal response mechanism of pear-jujube tree under the water deficit environment, and the effects of different deficit irrigation levels at different growth stages vegetative growth and repproductive growth of pear-jujube trees, and also its regulation mechanism.This paper also analyses the effect of water deficit on water use, yield, fruit quality, crop coefficient, water use efficiency and economical benefit, and achieved the followings:⑴The research of the water deficit treatment and rewater domino effect significantly test that proper water deficit can regulate and control stomal open degree efficiently, reduce the overtranspiration of leaves, stimulate the compensating effects. It also primarily reveals the mechanism of the regulated deficit irrigation which can enhance the leaf water use efficiency, the mechanism of regulation and control to the stomata caused by"dry-wet alternative process"originated from the water deficit, and also the mechanism of physiological water saving of the regulated deficit irrigation from physiology of the fruit tree.⑵It reveals the control process to the growth of pear-jujube tree which is caused by the regulated deficit irrigation, primarily illuminates the cause of the effects of different deficit irrigation levels at different growth stages on the vegetative growth and reproductive growth of pear-jujube trees, the fruit growth and the yield of the pear-jujube and offers a theory basis for the enhancement in the yield of the pear-jujube and of water use efficiency.⑶The dynamics of the sap fluxes of pear-jujube tree in the greenhouse under different deficit irrigation treatments at different growth stages and its quantitive relationship with reference crop evapotranspiration and soil water content, indicate that different deficit irrigation treatments not only can decrease the irrigation water amount significantly, but also make the maximum decrease of the sap flow amount just be only by 10.5%, and even the phenomenon that the sap flow amount is a little bit higher than the reference crops is observed, which illustrates that the"dry-wet alternative"in the rootzone of pear-jujube tree under the treatment of water deficit can stimulate the root to produce significant compensating effects of water supping.The results of combination method of sap flow and micro-lysimeter indicate that the evapotranspiration were in accordance with those of soil water balance method, with relative error ranging from -6% to +17%, which can be used to directed establish the irrigation schedule.⑷This paper sduty the effects of different deficit irrigation levels at different growth stages on the fruit quality, analyzes the sensitivity of the special quality index of pear-jujube tree to the regulate and control of water and makes a evaluation on the comprehensive quality of pear-jujube tree by the entropy method and the primary component analysis method, and primarily establish the regulated quality by control water production function which is based on water-quality response mechanism of pear-jujube tree.⑸The water consumption and crop coefficient of pear-jujube tree with different deficit irrigation levels treatment under the condition of the greenhouse and oasis field, indicate that the two above change as a single-peak curve the whole during growth stages, with the maximum appears at the flowering to fruit set stage and the fruit maturation stage.⑹By using various water deficit treatments at different growth stages on pear-jujube tree planted in both greenhouse and oasis field, we do some researches on the relationship between leaf stable carbon isotope discrimination(△L) and leaf water use efficiency at the same stage, the relationship between final yield and yield WUE, and also the relationship between fruit stable carbon isotope discrimination, yield, yield WUE and water use amount. Results indicate that water deficit had significant effect on the△L and the△F at different growth stages, and the△L under different water deficit treatments appear negatively related to WUEi,WUEn on fruit maturation stage(P<0.05)and the related relationship is not obvious at other growth stages(P>0.05),△F is significantly negatively related with WUEy and yield at fruit maturation stage. Thus the△L can indicate leaf water use efficiency over whole growth stage under different water deficit condition, and it indicated WUEn superior to WUEi,),and the indicated effect of△F to WUEy,ETc is also quite well.⑺From the view of selecting the best schedule of regulated deficit irrigation (RDI) for pear-jujube tree, a multi-hierarchy index system for evaluating the integrated benefit of the RDI was established using the field experimental data during 2005～2007. A multi-hierarchy and multi-objective fuzzy evaluation mode1 for evaluating the integrated benefit of RDI was also established using the multi-hierarchy and multi-objective fuzzy theory. The impersonality weights coefficient of all hierarchy evaluation index were obtained using the information entropy theory, then combined with the subjective weights given by experts, we obtained the integrated weights objective for the multi-hierarchy evaluation index, which can improved the reliability of the model evaluation results. At the same time, RDI integrated benefits (RDIIB) of pear-jujube tree with different water deficit treatments during 2005～2007 was evaluated and sorted using the model. Results show that under the greenhouse condition, the RDI integrated benefits (RDIIB) of pear-jujube tree with moderate water deficit (1/2 of full irrigation) treatments is better; Under the field condition the severe(no irrigation) and moderate water deficit (1/2 of full irrigation) treatments at the fruit maturation stage, the combined severe water deficit(no irrigation) at the bud burst to leafing stage and moderate water deficit(1/2 of full irrigation) at the fruit maturation stage had the better RDIIB,the result are in line with the actual production.Therefore, the RDIIB evaluation model based on information entropy theory can provide the reliable technical guidance for the optimal RDI scheme of pear-jujube tree.⑻According to the regulated deficit irrigation experiment data and local rainfall data in 3 years, the application model of the regulated deficit irrigation for pear-jujube tree on different hydrological years in the semi-arid region of Northwest China is primarily established, and the applicability and potential to apply and spread the regulated deficit irrigation for pear-jujube tree in the semi-arid region of Northwest is also discussed.The result of the research shows that the proper application of the regulated deficit irrigation in pear-jujube orchard in the semi-arid regions of northwest can enhance the yield and water use efficiency in leaves, contributing to form the continuable fruit produce model with stable water saving and high fruit quality, and give some important guidance to promote the scientific development of the fruit production in this region.
|
PDF Full Text Request