Effects Of Fertilization System On Ammonia Volatilization And Greenhouse Gas Emission In Weibei Apple Orchard

The purpose of this study was to determine the amount of nitrogen loss of fertilizer nitrogen through ammonia volatilization and N₂O emission in apple orchards in Weibei dryland,and to provide basic data for accurate estimation of regional emissions of greenhouse gas emission sources from farmland soil in Weibei dryland.N₂O and CO₂emissions from apple orchards in Weibei dryland were monitored by set up different fertilization systems.The differences of two different NH₃ volatilization research methods in orchards were compared.The main results were:?1?Under the mode of concentrated strip fertilization in apple orchards,nitrogen applied deeply hardly lost through NH₃ volatilization.Under the recommended nitrogen application rate(pure N 400 kg·ha^-1)of 5 cm,NH₃ volatilization reached 115.9 kg N·ha^-11 and nitrogen loss rate was 29.0%.When the depth of nitrogen fertilizer applied to soil exceeds 10cm,ammonia volatilization loss was less than 1%.The cumulative ammonia volatilization at the depth of 5 cm measured by closed chamber intermittent air extraction method and sponge absorption method was 62.0 kg NH₃·ha^-11 and 37.7 kg NH₃·ha^-1,respectively.Compared with closed chamber intermittent air extraction method,the ammonia volatilization loss of sponge absorption method was 39.2%lower.Nitrogen loss rates measured by air extraction method and ventilation method were 21.3%and 12.9%respectively.?2?Apple expansion period was the main period of N₂O emission from apple orchards in Weibei dry plateau.Soil N₂O emissions during apple ripening and expansion period were determined by temperature.The total N₂O emissions from different treatments?October2017-October 2018?ranged from 1.14 kg·ha^-1to 4.46 kg·ha^-1.Compared with conventional fertilization treatments,the total N₂O emissions from optimized nitrogen reduction and combined application of organic and inorganic fertilizers decreased by 43.3%and 42.6%respectively.?3?The total nitrogen loss through NH₃ and N₂O was dominated by N₂O loss,and volatilization loss of fertilizer nitrogen NH₃ was 0.The N₂O losses were 4.46 kg·ha^-1,2.53kg·ha^-1and 2.56 kg·ha^-1under conventional high nitrogen,optimized nitrogen reduction and organic-inorganic combined treatment,respectively.Nitrogen loss rate through N₂O was0.27%,0.22%and 0.22%respectively in conventional high nitrogen,optimized nitrogen reduction and organic-inorganic combined treatment.?4?CO₂ emission from apple orchards in Weibei dry tableland showed obvious seasonal dynamic changes.Spearman rank correlation analysis of CO₂ emissions with soil temperature and water content showed that R²was between 0.75⁰.84 and 0.54⁰.56respectively.The average emission flux of soil CO₂ during apple growth period was 328 mg CO₂·ha^-1·d^-1352 mg CO₂·ha^-1·d^-1,with the highest emission and significant difference from other growth periods.CO₂ emissions in the year?October 2017-October 2018?were between 3,813.2 kg C·ha^-1and 4,121.6 kg C·ha^-1.Compared with conventional high nitrogen treatment,reduced nitrogen fertilizer can reduce soil carbon emissions by 3.6%⁴.7%.?5?Q₁₀ value calculated according to Arrhenius equation decreases with the increase of temperature and increases with the increase of soil moisture.Nitrogen application reduced Q₁₀0 value of soil respiration,and applying organic fertilizer was the lowest among all fertilization treatments.The Arrhenius-Hyperbolic equation model established can well simulated the annual CO₂ emissions of apple orchards in Weibei dry tableland,and the interpretation degree R² of the equation was about 0.71.The paired T test showed that there was no significant difference between the simulation results of Arrhenius-Hyperbolic equation model and the measured values,and the model simulation results were good.According to the temperature and humidity simulation,the annual CO₂ emission of soil ranged from 3,943.16 kg C·ha^-11 to 4,272.1 kg C·ha^-1,which was 3.4%⁴.2%higher than the actual converted cumulative value.