Effects Of Partial Rootzone Dryinngand Potassium At Apple Orchards In Loess Plateau Of Shaanxi Provinces

Soil drought in spring, low in available soil nutrients and incoordination in interactionbetween soil water and nutrition are main problems in high quality apple production inShaanxi apple orchards in the Loess Plateau. Therefore, research on nutrition and wateruptake, interaction and management in high quality apple production can help to improveyield and fruit quality. Soil nutrition status in many Shaanxi apple orchards were analysed inseveral years in present study, classified index of soil available nutrition was established andexperiment of potassium fertilizer with fertigation or soil injection was conducted in order toprovide data base for orchard fertilizer recommendation. Effect of partial rootzone drying onhydraulic conductance, photosynthesis, transpiration, fluorescent properties, water and nutritionuptake, water potential, yield and quality in mature apple trees in field conditions were conductedin several years in order to provide useful information on orchard water-saving irrigation. Thephysiological mechanism of water-potassium coupling on hydraulic conductance on applerootstock was tested, which could be useful in improving soil water and nutrition useefficiency and water and nutrition management in high quality production in apple orchardsin the Loess Plateau. The main results were as follows:1. Soil nutrition status from517apple orchards on0-40cm layer and97soil profiles at0-120cm at8counties in Shaanxi Weibei areas in the Loess Plateau were analyed andsurveyed in several years, and potassium experiments on soil application, fertigation andinjection were conducted preliminary. The result showed that the average content of soilorganic matter were11.35g.kg-1in Weibei apple growing areas, the content of ammoniumnitrogen was4.67±1.37mg.kg-1, alkali nitrogen was57.08mg.kg-1, available zinc was1.20mg.kg-1, available Mn was12.49mg.kg-1, available copper was1.46mg.kg-1, available boronwas0.56mg.kg-1, available iron was12.07mg.kg-1, and didn't change much in0-120cm soildepth profiles of orchards. The average content of nitrate nitrogen was22.86±24.98mg.kg-1and changed largely, NO3-N accumulating peak was mostly on40-60cm soil layer, soilnitrogen content were slightly high in80%tested orchards, available phosphorus contentwere mostly fitted in the standard range, mainly at0-40cm soil layer of soil application place, average available potassium content was177.22mg.kg-1, and changed largely, were mostlylow in standard. High quality fruit will be produced when soil average available potassiumcontent reach to258-290mg.kg－1, or soil application of600kg/hm2potassim or fertigationwith375kg/hm2or soil injection510kg/hm2potassium with water. Fertigation by soilinjection and black film mulching is the important tenchency of fertilizer application indryland orchards in the near future.2. The effects of whole rootzone drying (NI), partial rootzone drying(PRD), conventionalirrigation(CI), three irrigation modes on the water potential, gas exchange, leaf and shoothydraulic conductivity characteristics in the field conditons of the Loess Plateau were studiedin thirteen years Fuji apple trees orchard. The results indicated that leaf water potential andstem water potential reached the lowest valve in July, diurnal variations of water potentialreached the lowest valve in the14o 'clock, the order of leaf water potential and stem waterpotential in seasonal and diurnal variations were CI＞PRD＞NI. The leaf and shoothydraulic conductance presented a decreasing trend with the increase of drought, leafhydraulic conductance of PRD and NI reduced13.27%and42.01%, shoot hydraulicconductance of PRD and NI reduced3.01%and34.36%compared with that of CI. Butcompared with CI and NI, leaf area specific conductance and shoot area specific conductanceof PRD were enhanced by14.32%and14.43%,96.12%and16.55%, respectively. PRD had abigger leaf area specific conductance compared with CI and NI, however, value of RWC wasbetween the two treatments, it showed that in a certain RWC range, increase of leaf areaspecific conductance were at the cost of decreasing some RWC. Compared with CI and NI,WUE of PRD greatly improved29.08%and26.82%, and its maximum net photosyntheticrate, apparent quantum efficiemty and dark respiration rate were between the CI and NI.Water defict reduced leaf area, shoot length and photosynthetic indexes.3. When soil moisture content on the dry side in half rootzone irrigation was low, appleroots on the irrigated rootzone side increased water uptake to make up for its water deficit andapple roots on the dry side improved water uptake in deeper soil layers. There was more rootsdistribution under0-50mm depths of Fuji apple tree to uptake more water, there was less rootsunder the50-180cm depth, but the trees also had an effect on absorbing water. Longtermdrying easily resulted in smaller apple fruit, higher soluble solids content and flesh firmnes,lower titratable acid. Apple yield presented a trend of biennial fruting and nonuniform fruitsize distribution in half rootzone drying treatment. Ratio of energy transfer and energy absorbin ET0/TR0reaction Center in the course of the day was a bimodal curve, normal irrigation>not irrigation> half root irrigation. Maximum effective light energy utilization of TRo/ABSand RC/ABS units of the reaction Center absorb energy had an tendency with the first decrease and then increase on the day, conventional irrigation> half rootzone drying> wholerootzone drying.4. The effects of water-potassium coupling on hydraulic conductance, leaf area specificconductance, sapwood area specific conductance of root, stem, leaf, plant of Malushupehensis were studied. Three water levels and three potassium levels were set, hydraulicarchitecture of Malus hupehensis were measured with the high pressure flow meter (HPFM).on the high potassium level, water deficit greatly decreased hydraulic conductance of root,leaf and plant, leaf area specific conductance of leaf and plant, sapwood area specificconductance of plant of Malus hupehensis, the leaf area specific conductance of leaf in themoderate and severe water stress reduced to the35%and29%of normal water conditionsrespectively. On the normal irrigation conditions and potassium addition on the high level cangreatly enhanced hydraulic conductance of root and plant; greatly enhanced leaf area specificconductance of root, leaf and plant; also greatly enhanced sapwood area specific conductanceof plant of Malus hupehensis. The leaf area specific conductance of leaf in the high andexcessive high potassium level were increased by17%and lowered27%compared with lowpotassium level respectively. In the severe water deficit, stomatal conductance in the highpotassium level increases by28%compared with low potassium level. Water deficit andpotassium addition treatment decreased leaf water potential and induced xylem embolism.Water deficit reduced stomatial conductance(GS), however, potassium can decreased thisresult on some levels. Potassium addition greatly decreased leaf water potential of the plantssubjected to water deficit, induced xylem embolism and limited water lost further in this way.