| Apple is one of the major economic crops in the Weibei dryland,Shaanxi Province,China that considered as main source of income for farmers.Long-term poor management of apple orchard such as non-soil mulching,excess fertilizers and insecticides applications induce greenhouse gas emissions;reduce soil quality and apple yields.Hence,to address these challenges that apple orchard faced in China,the following objectives have been established:to examine the effects of Brassica napus combined with organic and inorganic applications on soil physic-chemical properties and yield of apple orchard in Weibei dryland,to quantify GHG emissions（CO2,N2O,and CH4）in apples orchard under the application of Brassica napus combined with organic and inorganic,to investigate the effect of Brassica napus as cover crop combined with organic and inorganic applications on global warming potential（GWP）,greenhouse gas intensity（GHGI）and direct N2O emission factors（N2O EFd）,to evaluate the effect of black polyethylene plastic film mulching combined with organic and inorganic fertilizers on GHG emissions and GHGI in apple orchard,and to evaluate the effects of combined organic and inorganic on GHG emissions between fertilizer ditches（FD）and bare soil（BS）sites,and to assess the GWP,GHGI and GHG emissions in apple orchard.The experiment was carried out at the Weibei Dryland Experimental Station of Northwest A&F University（started in 2008）.This research was conducted over a three-year period,since 2018 to 2020.The experiment was set up with two factorial designs arranged in split-plot design with three replicates.The main plot of this experiment consisted on mulching（Brassica napus as cover crop,and black polyethylene plastic film mulching）and clean tillage.In addition,control（CK）,organic fertilizer（M）,inorganic fertilizer（NPK）,and organic combined with inorganic fertilizer（MNPK）were arranged in sub-plots.The results of this study were summarized as follow:1.The combination of cover crop（Brassica napus）with organic and inorganic fertilizers had a significant effect on the physical and chemical properties of the soil and the apple yield.The soil under Brassica napus as cover crop（CC）increased the accumulated amount of soil macroporosity,the number of macropores,water-filled pore space（WFPS）,total nitrogen（TN）,available phosphorus（AP）,available potassium（AK）,soil organic matter（SOM）,ammonium nitrate（NH4+-N）,nitrate nitrogen（NO3--N）,and reduced soil bulk density.The overall average was about 42.42%,34.04%,12.56%,21%,12.57%,17.15%,26.93%,26.29%,18.17%,and 6.69%,respectively,compared to clean tillage（CT）.However,for soil p H under CC and CT,there was no significant difference observed.The soil under the CC site with the MNPK treatment significantly increased the fertility of the soil based on the different soil layers.It was found that the depth of the soil layer from 0 to20 cm was augmented by 71.41%of the amount of accumulation of TN,160.78%of AP,and225.60%of AK compared to the CK treatment（p<0.05）.At the same time,in the soil layer of 20 to 40cm under CC in MNPK treatment was significantly increased by the accumulated amounts of TN,AP,and AK increased by 89.50%,154.48%,and 228.36%,respectively,compared to CK treatment.On the other hand,for the average soil bulk density in MNPK treatment,was approximately 1.50 g cm-3 in 0 to 20 cm and approximately 1.57 g cm-3 in 20to 40 cm,which is equal to a decrease of 14.48%and approximately 13.20%,respectively,by comparing with CK treatment.It was also found that the mean apple yield under the site of soil covered by Brassica napus was improved up to 48.16 t ha-1,which means 25.07%compared to CT.Moreover,the soil under CC in MNPK treatment boosted significantly the average yield of apples by 131.41%compared to CK treatment.Therefore,this experiment showed that the application of Brassica napus combined with organic and inorganic fertilizers（MNPK）increased the amount of nutrients in the soil,and apple yield increased significantly.2.Combination of cover crop（Brassica napus）with organic and inorganic fertilizers had a significant impact on increase of GHG emissions.Hence,the use of Brassica napus as cover crop（CC）increased significantly the total cumulative amount of N2O and CO2emissions by about 27%and 23.48%,respectively,compared to clean tillage（CT）.But the total accumulated amount of CH4 was all negative,which showed that CH4 was uptake in dryland,and the soil under CC has reduced the accumulated amount of CH4 uptake to approximately 19.01%compared to CT.The increase in GHG emissions（N2O and CO2）in soil under CC has significantly affected the increase in global warming potential（GWP）,greenhouse gas intensity（GHGI）,direct N2O emission factor（N2O EFd）,and nitrogen agronomic efficiency（NAE）.The average increase was about 39.69%,12.04%,21.51%,and25.59%,respectively,compared to CT.However,for yield-scaled N2O emission（YSNE）the soil under CC was augmented around 0.05 kg t-1 and under CT soil approximately 0.04 kg t-1,which was not significantly different from CC and CT soil.The soil under the application of Brassica napus as cover crop with organic and inorganic fertilizers（MNPK）had a significant impact on increase GHG emissions.In particular,the cumulative amount of N2O emissions was increased by 101.77%and CO2 emissions increased by 90.89%compared to the CK treatment.But for the accumulation amount of CH4 uptake has increased significantly within M treatment by 291.22%compared to CK treatment.Additionally,it appeared that the cumulative amount of GHGI in MNPK treatment has significantly decreased to approximately 12.79%and 29.80%,respectively,compared to CK and NPK treatments.These results demonstrated that the application of Brassica napus as cover crop with organic and inorganic（MNPK）in apple orchard in Weibei dryland increased GHG emissions,GWP,and reduced GHGI.3.The combination of black polyethylene plastic film mulching with organic and inorganic fertilizers had a significant impact on increase of GHG emissions.The soil under the application of black polyethylene plastic film mulching（PM）increased the cumulative N2O emission by approximately 58.62%,the CO2 emission 38.99%while the cumulative CH4 uptake was reduced by around 31.99%compared to non-mulching（NM）.Moreover,it was found that the average cumulative amount of GWP and GHGI under soil covered by PM were highly significant augmented by approximately 77.60%and 65.05%,respectively,compared with NM.The soil under the application of black polyethylene plastic film mulching combined with organic and inorganic（MNPK）boosted significantly the cumulative N2O and CO2 emissions on average of 215.40%and 126.17%,respectively,compared to CK.Furthermore,the cumulative amount of CH4 uptake augmented in M treatment by around 175.24%compared to CK treatment,while the cumulative amount of GWP in MNPK treatment has significantly increased by the average of 222.07%compared to CK treatment.On the other hand,the cumulative amount of GHGI in MNPK was reduced about 37.92%,which was significantly lower compared to NPK treatment.4.The soil under fertilizer ditch sites combined with organic and inorganic fertilizer applications in apple orchard had a significant impact on increase of GHG emissions.The soil under the fertilizer ditch（FD）increased the accumulated amount of N2O and CO2emissions and reduced the accumulated amount of CH4 uptake by an average of 105.72%,23.63%,and 12.07%,respectively,compared to the bare soil（BS）.At the same time,under fertilizer ditch soil（FD）,the cumulative amount of GWP,GHGI,N2O EFd,and YSNE increased by approximately 129.90%,100.85%,176.88%,and 81.44%,respectively,compared to the soil under BS.In the soil under FD sites in MNPK treatment,it was found an increase of accumulated amount of N2O and CO2 emissions by approximately 10.73%and 51.66%,respectively,compared to NPK treatment.In contrast,for the cumulative amount of CH4 uptake in the soil under MNPK treatment was reduced by approximately27.53%compared to M treatment.It was also found that when comparing the NPK and MNPK treatments,the total cumulative amount of GWP in the MNPK treatment increased by approximately 9.29%,which was higher than the NPK treatment,but there was no significant difference between the two treatments.However,the cumulative amount of GHGI in the MNPK treatment was reduced by approximately 30.83%compared to the NPK treatment.These results show that although MNPK treatment in the soil FD sites increased the cumulative amount of GHG and GWP emissions were higher than other treatments,but on the other hand,it can also significantly reduce the cumulative amount of GHGI.Finally,as conclusion of our study the soil under the application of Brassica napus as cover crop（CC）,black polyethylene plastic film mulching（PM）,and the soil under fertilizer ditches（FD）that were combined with organic and inorganic fertilizers in MNPK treatment had a significant effect on increasing soil nutrients,apple yield,the amount of accumulation of CO2,N2O emissions,and reducing the amount of accumulation of CH4 uptake.In addition to the application of soil mulching combined with different types of fertilizers,we also found that environmental factors are also important determinants that have a significant impact on GHG emissions in apple orchard.The accumulation of N2O emissions was mainly affected and positively correlated with the increase of air temperature,soil temperature,WFPS,soil macroporosity,number of macropores,and NO3--N,but the accumulation of N2O emissions has a negative relationship with soil bulk density.At the same time,the average accumulation of CO2 emissions is positively correlated with SOM,and other factors are similar to N2O emissions.Moreover,the cumulative amount of CH4 uptake was influenced by soil bulk density,which has a positive relationship,and it was also found that CH4 uptake has a negative relationship with the content of NH4+-N,NO3--N,and WFPS contents.Overall,our study found that the soil under the application of Brassica napus as cover crop（CC）,black polyethylene plastic film mulching（PM）,and fertilizer ditch（FD）combined with organic and inorganic fertilizers had a significant effect on increasing soil nutrients,apple yield,and reducing the amount of GHGI.Hence,those management methods were appropriate and friendly to the environment,and enabled the sustainable development of an apple orchard. |
