Soil Water Uptake By Dwarfing Young Apple Tree Under Different Water Storage Pit Irrigation Quotas

As a mid-deep three-dimensional new irrigation method,water storage pit irrigatation is different from other traditional irrigations in soil moisture and root growth distribution which will influence the uptake depth of the tree.Hydrogen and oxygen stable isotopes have head start in plant water source research,yet the precondition applying this technology is precise water stable isotopes datas.This paper,by takeing five years old young apple trees as materials,using cryogenic vaccum distillation to extract plant and soil water samples,analyzing the influence of extract time and sample isotope datas under different tube filler,water content and nitrogenous fertilizer level treatments.Base on the best time to confirm the uptake of the setting treatments which are one surface irrigation(CK,was irrigated 90m3 in unit of area)and three water storage irrigation ways(WSP-1,WSP-2,WSP-3,were separately irrigated 90m3,24m3,18m3 in unit of area),and draws the following main conclusions:(1)Study on the influence of extract time and wanter isotopes by cryogenic vacuum distillation: 1)when the extacct gradient time was 30 minute,the sponge(T1),the silica wool(T2),the pledget(T3)and the acticarbon filtration wool(T4)treatments’ isotopes were stable,at the same time the T1 treatment variance within group was the minimum,so it could be regarded as the best tube filler.2)The minimum extract time and water sample isotopes were effected by different moisture content level in loamy soil.All water can be extracted with 30 minutes,if the moisture content below 12%.The extract time was 60 minutes,when the moisture content between 18% and 24%.If the moisture content was 30%,the extract time will prolong to 90 minutes.T test indicated that δ18O of W1 and W2 treatments were significant different from standard samples,no significant difference in W3 and W4 treatments,but if the extract time prolong to 135 min the W4 treatments water sample was affected.So may not the longer extact time,the better analysis results.3)The shortest extract time was not influence by nitrogenous fertilizer levels,but the sample isotopes were.When the extract time was 60 minutes,the water extraction efficiency reached 100%.T test indicated that the water sample isotopes beyond the permissible range,if the nitrogen fertilizer level was 300mg/kg.4)The extract time of the xylem of branch on five years old tree was 75 minutes.(2)Study on soil water uptake for yong apple tree under the different quotas: Using δD and δ18O of 80 precipition samples from April to November,fitting the local precipitation curve for taigu town,result was as follow: δD=7.481δ18O+2.4329(R2=0.971).All of the treatments absorbed the surface water source in early growth stages,but along with the growth stages,root uptake depth was deeper,in the later growth stages,uptake depths shallowed again.1)In early stage,four treatments uptake depth were same,but from branch pausing stage CK treatment uptake depth was superficial than water storage pit irrigations’,the latter advantage was appeared.CK treatment uptake depth was 17.00 cm,28.36 cm in germination stage,the new branch shooting was 24.51 cm.WSP-1,WSP-2 and WSP-3 treatment uptake depth were 21.20cm;23.70cm;23.70 cm in germination stage,the new branch shooting were 23.76cm;25.44cm;25.09 cm.All of the treatment major contribution soil layer were 0-20 cm in those two stages.2)Precipitation in july have a bigger influence in CK and WSP-1 treatment than WSP-2 and WSP-3 treatment,also cause effect in the surface layer of the treatment results.In branch second shooting stage,CK treatment uptake depth were 25.56 cm,55.23 cm,129.31 cm,the major contribution soil layer were 0-60 cm,120-140 cm.WSP-1 treatment uptake depth were 23.92 cm,78.65 cm,140.73 cm,the major contribution soil layer were 40-80 cm,120-140 cm.WSP-2 and WSP-3 treatment uptake depth were 54.75cm;16.72 cm,60.59 cm,the major contribution soil layer both were 0-40 cm.3)the ablitiy of using deep soil water of WSP-1 treatment was greater than WSP-2 and WSP-3 treatment,CK treatment was the lowest in fruit expanding stage.CK treatment uptake depth was 39.31 cm,the major contribution soil layer was 0-40 cm.WSP-1,WSP-2 and WSP-3 treatment uptake depth were 47.36 cm,122.48cm;30.34 cm,71.56cm;30.23 cm,66.96 cm,the major contribution soil layer were 40-120cm;20-60cm;20-60 cm.4)All treatments soil water uptake become shallow in fruit riping stage,but this phenomenon was obvious in the water storage pit irrigation with small irrigation quota.The soil water uptake depth were 43.73cm;44.67cm;32.05cm;33.22 cm,the major contribution soil layer were 0-40cm;20-60cm;0-20cm;0-20 cm.(3)From the rate of contribution and uptake depths in germination stage,new branch shooting stage and branch pausing stage under water storage pit irrigation treatments,we can find that WSP-2 and WSP-3 treatments maximum rate of contribution and the uptake depth were same as WSP-1,so we can deem that it not need too large irrigation quota to meet apple tree water demand,overlarge irrigation quota may cause deep percolation and reduce the irrigation water use efficiency yet.(4)From the results of four models that the driect inference method is direct and sample,but it can not infer the uptake depth beyond the soil partition,water absorption depth model can remedy this flaw,combining these two approach can give the uptake depth.Although the coupling model computation results were larger in later growth stages,multiple source liner model can reduce error by taking reprated combination calculation,both of them can confirm the rate of contribution.Those four models learn from each other and narrow the range,so that they can let the uptake depth more accurate.