Effects Of Different Water And Fertilizer Management On Greenhouse Gas Emissions In Apple Orchard In Weibei Dryland

The Weibei dry tableland is the eugenics area of apple industry.Irrational fertilization and long-term clear tillage system will worsen the soil environment and reduce the yield and quality of orchard.In order to improve and solve these problems existing in the orchard,this study,based on the 12-year long-term positioning experiment,set the main treatment for growing grass and clear tillage,and the secondary treatments were no fertilization（CK）,chemical fertilizer only（NPK）and organo-inorganic combined application（MNPK）.Respectively for 2019 years apple orchard grass coverage and soil fertility in different fertilization treatment effect,production effect and environmental effect were evaluated,aims to explore the sward and organic inorganic NPK several effect under two kinds of management measures,for managemat pattern apple orchard soil effective water management to provide theoretical basis and technical support,has the following main conclusions:1.Combined application of organic and inorganic fertilizers could significantly increase soil nutrient content,improve soil porosity,effectively increase soil nitrogen agronomic efficiency（NAE）,and increase fruit yield.Compared with NPK treatment,the contents of soil organic matter,total nitrogen,available phosphorus and available potassium in MNPK treatment showed a decreasing trend with the deepening of soil layer.In the 0～20 cm soil layer,the contents of soil organic matter and soil total nitrogen under MNPK treatment increased by 16.6%and 33.1%,respectively,and the contents of soil available P and available K increased by 63.7%and 34.2%,respectively,compared with that under NPK treatment.Compared with NPK treatment,the contents of soil organic matter,total nitrogen,available phosphorus and available potassium in 20～40 cm soil layer under MNPK treatment increased by 45.5%,36.9%,23.7%and 43.1%,respectively.Compared with NPK treatment,MNPK treatment significantly increased the soil porosity and the number of soil macropores.In the 0～20cm soil layer,the soil porosity and the number of soil macropores increased by52.2%and 27.2%,respectively.In the 20～40cm soil layer,The soil porosity and the number of soil macropores under MNPK treatment were significantly higher than those under NPK treatment（61.3%and 92.4%）.In addition,compared with NPK treatment,MNPK treatment increased agronomic efficiency by 114.3%and yield by 39.7%.2.Combined application of organic and inorganic fertilizers can increase methane（CH₄）uptake,nitrous oxide（N₂O）and carbon dioxide（CO₂）emissions,and increase the comprehensive warming potential（TGWP）,but reduce greenhouse gas emission intensity（GHGI）.Compared with NPK treatment,MNPK treatment increased CH₄ cumulative uptake by 23.2%,CO₂ cumulative emission by 9.4%,N₂O cumulative emission by 26.1%,comprehensive warming potential by 26.3%,and greenhouse gas emission intensity（GHGI）by 22.8%.The combined application of organic and inorganic fertilizers significantly increased the N₂O emission coefficient,and the N₂O emission coefficient increased by 51.5%compared with the single application of chemical fertilizer.The N₂O emission coefficient per unit yield of the combined application of organic and inorganic fertilizers was 0.05kg·t^-1,which was not significantly different from that of the single application of chemical fertilizer and no fertilizer treatment.3.Long-term cover crop in orchards can significantly increase soil fertility,soil porosity and the number of macropores,and increase fruit yield.The soil available nutrients under the long-term grass treatment were all the same as that under the green grass treatment>in the0～40 cm soil layer,and the contents of available nutrients decreased with the deepening of soil layer.Compared with clear tillage treatment,the soil organic matter content,total nitrogen content,available potassium content and available phosphorus content in 0～20 cm soil layer increased by 20.4%,28.3%,23.4%and 28.5%respectively.In the 20～40 cm soil layer,the organic matter content,total nitrogen content and available potassium content in the soil under grass treatment increased by 13.1%,26.5%and 16.4%compared with that under clear tillage treatment.In addition,the soil porosity of grass treatment increased by83.1%and 29.5%in 0～20 cm soil layer and 20～40 cm soil layer,respectively.The yield of grass treatment was higher than that of clear tillage treatment,and the yield increase rate was24.8%.4.Long-term grass mulching in orchard decreased soil N₂O emission,increased soil CH₄ absorption and CO₂ emission.Compared with clear tillage,the cumulative absorption of CH₄ was decreased by 30.1%and the cumulative emission of CO₂ was increased by 8.9%under grass cropping mode.The cumulative emission of N₂O was 0.87 kg·hm^-2,which was18.4%higher than that under clear tillage.The comprehensive greenhouse effect of grass and clear tillage treatment was 198.13 and 225.55 kg·hm^-2,respectively,and there was no significant difference between the two treatments.Soil greenhouse gas emission intensity（GHGI）was significantly different between green grass and clear tillage,and the GHGI of soil under green grass treatment was 32.1%lower than that under clear tillage.In conclusion,long-term grass planting in dryland apple orchards is beneficial to reduce the comprehensive warming potential and greenhouse gas emission intensity,and this management measure is beneficial to the sustainable development of apple orchards.5.The interaction of grass mulch and organic and inorganic application had significant effects on the cumulative emissions of CH₄,CO₂ and N₂O.Compared with NPK treatment,MNPK treatment significantly reduced the cumulative emission of N₂O gas and the cumulative absorption of CH₄,but significantly increased the cumulative emission of CO₂under grass cover condition.Compared with NPK treatment,MNPK treatment significantly reduced the cumulative CH₄ uptake and CO₂ emissions,but had no significant effect on soil N₂O emissions under clear tillage.Correlation analysis showed that CH₄ emission was positively correlated with soil water content and negatively correlated with NH₄⁺-N.CO₂emission was negatively correlated with soil water content and NH₄⁺-N content;N₂O emission was mainly affected by soil NO₃^--N.Soil N₂O emission was negatively correlated with soil bulk density,but positively correlated with soil porosity and macropore number.Soil CH₄ emission was negatively correlated with soil porosity and macropore number,indicating that soil porosity and hydrothermal conditions were the main factors affecting greenhouse gas emission.