Comparative Study On Ecosystem Services Of Surface And Subsurface Drip Irrigation In Apple Orchards

The Loess Plateau was a typical arid and semi-arid climate area,with less rainfall,large evaporation and serious seasonal drought and water shortage,which restricted the green and sustainable development of local agriculture.Irrigation as a farmland management measure to regulate soil moisture,the change of its method would lead to the changes of soil moisture distribution,soil environment,microbial activity and greenhouse gas emission characteristics,and whether it would affect the ecosystem services of apple orchard ecosystem services remains to be further studied.Based on this,the paper used a combination of field experiment and Meta-analysis to investigate the effects between surface and subsurface drip irrigation on the ecosystem services of apple orchards in Weibei Loess Plateau,and to explore the influence mechanism of irrigation methods on greenhouse gas emissions.The following conclusions were obtained:（1）Irrigation methods had a significant effect on regulation services of apple orchard.Compared with no irrigation（CK）,drip irrigation（DI）significantly increased soil moisture content and soil evaporation in 0 cm-20 cm soil layer,and significantly reduced soil p H.Subsurface drip irrigation（SDI）treatment significantly increased the soil moisture content,electrical conductivity and organic carbon of 20 cm-60 cm soil,while significantly reduced soil p H.In addition,compared with CK,the CO₂and N₂O emission fluxes under DI and SDI treatments were significantly increased,while there was no significant difference in CO₂emission flux between SDI and DI,and SDI treatment were significantly lower than DI in N₂O emission flux.CK treatment was significantly higher than DI and SDI treatment in CH₄absorption flux,and there was no significant difference between SDI and DI.（2）Irrigation methods had a significant effect on soil nitrate nitrogen,but not on ammonium nitrogen in apple orchard support services.Irrigation methods had a significant effect on the supply services.The root length density,root surface area and root volume density of DI treatment were higher than those of SDI treatment at 0 cm-20 cm,and lower than those of SDI treatment at 20 cm-60 cm,indicating that SDI treatment was beneficial to root ligation.CK treated roots would grow deeper and absorb water to maintain growth.The order of net photosynthetic rate Pn,transpiration rate Tr,stomatal conductance Gs and intercellular CO₂concentration Ci of apple leaves was SDI>DI>CK.Compared with CK,DI and SDI treatments significantly increased apple pericarp malleability,single fruit weight,transverse diameter and longitudinal diameter.DI treatment significantly decreased pericarp hardness,and SDI treatment significantly increased apple yield.The effect of different irrigation methods on pulp hardnes,pulp crispness,pulp firmness,titratable acid,soluble solids and fruit color difference were not significant.（3）There were differences in response rules between greenhouse gas emissions and soil physical and chemical properties under different irrigation methods.The CO₂and N₂O emission fluxes of different irrigation methods were significantly correlated with soil moisture content and soil temperature.The N₂O emission flux of DI treatment was significantly positively correlated with soil moisture content,the CO₂emission flux of SDI treatment was significantly positively correlated with soil moisture content,and the CO₂and N₂O emission flux of CK treatment were significantly negatively correlated with soil moisture content.There was a significant positive correlation between N₂O emission flux and soil temperature under the condition that no large amount of nitrogen fertilizer（base fertilizer）was applied at the early stage of the experiment.Affected by irrigation methods,CO₂and N₂O emission fluxes under DI treatment were significantly positively correlated with nitrate nitrogen,while the CO₂emission flux in SDI treatment was significantly positively correlated with nitrate nitrogen.The CH₄emission flux under DI treatment was significantly positively correlated with ammonium nitrogen,while the CO₂,N₂O and CH₄emission fluxes under other treatments were not significantly correlated with ammonium nitrogen and p H.（4）There were differences in the trade-off and synergistic relationship of ecosystem services in apple orchard under different irrigation methods.In the orchards treated by DI and SDI,there was a synergistic relationship between soil moisture content,soil evaporation,p H,CO₂and N₂O,while there was a synergistic relationship between nitrate nitrogen and soil evaporation,CO₂and N₂O.In the orchard treated by CK,there was a trade-off relationship between soil moisture content and soil temperature,soil evaporation,p H,CO₂,N₂O and nitrate nitrogen,while there was a synergistic relationship between soil temperature,soil evaporation,p H,CO₂,N₂O and nitrate nitrogen.The yield and soil water content of apple orchard treated by SDI were higher,and the emission of CO₂and N₂O were lower.In order to maximize the orchard resources and benefits,subsurface drip irrigation was an ideal irrigation method.