| In recent years,with the rapid development of fruit industry in China,the planting area and yield of fruit trees have ranked first in the world.However,the drip irrigation system layout and the irrigation decision-making methods of orchards in most areas of northern China are unreasonable,leading to low water-use efficiency(WUE)and serious agricultural water waste Therefore,further research on the e fficient irrigation modes in orchards,and proposing suitable drip irrigation methods and water management thresholds for fruit trees are of great significance for improving the water use coefficient of orchards and alleviating water pressure.This study taked the 9 year old pear(Pyrus pyrifolia cv Whangkeumbae)as the experimental crop to conduct a one-year field irrigation experiment,two experiments were set up with two factors of soil moisture regulation and drip irrigation method under the background of drip irrigation In Experiment 1,the lower limit of soil moisture was taken as the variable,and set up three experimental groups:T1(80%of the field water capacity,namely 0.8 FC),T2(0.7 FC),T3(0.6 FC)and one control group CK,with the upper limit of soil moisture as FC In Experiment 2,the drip irrigation method was taken as the variable,and three experimental groups were set up:M1(the surface double lines drip irrigation),M2(the subsurface double lines drip irrigation),M3(the surface ring drip irrigation)and one control group CK(the surface single line drip irrigation)By regularly measuring soil moisture,Nitrogen,pear tree growth indexes,water consumption,yield and fruit quality,etc.,analyze the effects of different experimental treatments on fruit tree root water absorption,vegetative growth and reproductive growth,and WUE,and comprehensively evaluate the optimal drip irrigation mode for pear orchards.The main conclusions of this paper were as follows:(1)The increase of soil moisture was related to irrigation and precipitation,while the consumption was mainly affected by the root system The lower the control limit of soil moisture,the lower the soil moisture content,and the bigger the coefficient of variation.When the lower limit of soil moisture was controlled at 0.7 FC,the water consumption in the main root zone of the soil profile was the largest,the soil moisture content was low,and there was a large range of variation area,indicating that the pear roots in this range had strong root vitality and strong water absorption,which was conducive to the growth and development of pear trees.In addition,the subsurface drip irrigation had greater variation in the shallow soil moisture than the surface drip irrigation;the spatial distribution of the soil moisture variation coefficient of the ring drip irrigation was more uniform,which was more conducive to the uniform growth of the root system.(2)With the progress of the experiment,the content of nitrate nitrogen gradually increased,and the content of ammonium nitrogen gradually decreased;the two index values in the whole soil profile fluctuated widely before the test,and the distribution of nitrate nitrogen and ammonium nitrogen after the test was more uniform than before the test.The reasons for the increase in nitrate nitrogen content might be affected by the types of fertilizers,nitrification reaction and composting,etc.,and further research is needed.After the test,the ammonium nitrogen presented a phenomenon of low surface layer and high depth layer,and the lower the lower limit of soil moisture,the weaker the leaching loss of water to ammonium nitrogen,and the lower the value of deep ammonium nitrogen.(3)In terms of growth indicators of pear trees,the growth trend of shoot stems and fruits was "slow-fast-slow" during the growth period,and there was a restrictive relationship between them.When the lower limit of soil moisture was controlled at 0.7 FC,the length and diameter of shoot stems were the smallest,the growth of new shoots of CK was the best.However,the yield under the lower limit of soil moisture was controlled at 0.7 FC was increased by 16.11%higher than the yield of CK In the drip irrigation method experiment,the growth of shoot stems under the subsurface drip irrigation was the worst,but the yield was significantly increased by 16.36%～33.57%compared with other treatments It showed that the amount of irrigation and yield were not linear,and proper control of soil moisture can inhibit excessive vegetative growth and promote reproductive growth.(4)Within a certain range,the total water consumption was positively correlated with the irrigation amount With the decrease of the lower limit of soil moisture,the irrigation amount decreased,and the total water consumption decreased gradually.The CK was significantly higher than that of the other experimental groups(p<0.05)The drip irrigation methods had no significant effect on the water consumption of fruit trees,but the total water consumption of the subsurface drip irrigation was lower than that of the surface drip irrigation,and the total water consumption of the ring drip irrigation was lower than that of the double lines parallel drip irrigation Combined with the yield,it was found that the WUE of T2 was the highest,which was 4.41 kg/m3,which was increased by 7.56%and 12.21%compared with T1 and T3,respectively,and did not have a significant impact.In the drip irrigation method experiment,the maximum WUE of M2 was 5.54 kg/m3,which was significantly different from the M1.The WUE of the M3 was 0.61 kg/m3 higher than the M1,but the difference was not significant.The results of the two experiments showed that the WUE of the experimental groups were 24.24%～67.88%higher than that of the CK,and the difference was significant,indicating that the current WUE of the orchard had a great improvement space.(5)Appropriately lowering the lower limit of soil moisture could improve fruit quality,which is significant in soluble solids,titratable acidity and reduced Vc.Different drip irrigation methods had no significant effect on the fruit quality indicators,but it could be seen that the index values of soluble total sugar and reduced Vc of the three test groups were higher than the control group,especially for subsurface drip irrigation.The values of titratable acidity of the subsurface drip irrigation was better than surface drip irrigation,and the ring drip irrigation was better than the double lines parallel drip irrigation.The total nitrogen content of the ring drip irrigation treatment was significantly higher than the other three treatments.It showed that the subsurface drip irrigation and ring drip irrigation treatment were more beneficial to improve the quality of pears(6)Based on the characteristics of root water absorption,growth indicators,water consumption of pear trees,WUE and fruit quality,the best irrigation combination mode of pear orchard in this area is recommended:the lower limit of soil moisture control is 0.7 FC;the drip irrigation method should be subsurface drip irrigation or ring drip irrigation. |
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