Effect Of Different Nitrogen Application Conditions On Ammonia Volatilization In Apple Orchards Under Water Storage Pit Irrigation

Water storage pit irrigation is a mid-deep three-dimensional irrigation method suitable for orchards in hilly areas.It has the advantages of reducing surface evaporation and rainwater storage,and can solve the problems of drought and soil erosion in the Loess Plateau.Nitrogen is an important nutrient for crop growth.Due to the lack of reasonable irrigation system,the utilization rate of nitrogen fertilizer in China is low and the loss of nitrogen is serious.Ammonia volatilization is an important way of nitrogen loss after the application of nitrogen fertilizer in farmland.Based on the water storage pit irrigation method,the study of ammonia volatilization in orchard soil under different nitrogen application conditions has important guiding significance for formulating a scientific and reasonable water and fertilizer management system,improving water and fertilizer utilization rate and developing ecological agricultureThe experiment was conducted in the water-saving irrigation demonstration garden of Fruit Tree Institute of Shanxi Academy of Agricultural Sciences from April to September,2018.The experiment took the period of fertilizer application and the amount of fertilizer application as the control factors.The effects of different nitrogen application conditions on ammonia volatilization rate,ammonia volatilization accumulation and nitrogen loss rate in apple orchard soil under water storage pit irrigation were studied.The effects of water storage pit irrigation and surface irrigation conditions on ammonia volatilization were compared Finally,the effects of soil physical and chemical properties and meteorological factors on ammonia volatilization rate were analyzed.The results of this experiment are as follows:1.Fertilization significantly increased the rate of ammonia volatilization in soil.After fertilization,the rate of ammonia volatilization increased first,then decreased,and finally tended to be near the baseline.Different topdressing amount and topdressing period will produce different ammonia volatilization process.The higher topdressing amount is,the higher the ammonia volatilization rate is.The magnitude and peak time of ammonia volatilization rate are related to topdressing period.The ammonia volatilization rate is small in late flowering period,the peak value occurs in the 3rd to 5th day after fertilization.The ammonia volatilization rate in fruit expansion period increases,and the peak value occurs on the 2nd day after fertilization.The ammonia volatilization rate decreased faster in fruit expansion period than in later flowering period.The ammonia volatilization rate of water storage pit irrigation treatment is mainly concentrated in the wall of storage pit,and the surface soil ammonia volatilization rate is low.The ammonia volatilization rate of surface irrigation treatment is about 3.5?6.4 times of the ammonia volatilization rate of the wall of water storage pit(F5).2.The effects of soil physical and chemical properties and meteorological factors on ammonia volatilization rate were different.Surface soil ammonium nitrogen concentration and soil pH were the determinants of ammonia volatilization rate.Ammonia volatilization rate was significantly or very significantly positively correlated with surface soil ammonium nitrogen concentration and soil pH.The correlation between ammonia volatilization rate and soil temperature was lower in late flowering stage and there was a significant positive correlation after the removal of special points in the fruit expansion stage.After topdressing,ammonia volatilization rate was significantly positively correlated with air temperature.Ammonia volatilization rate was positively correlated with solar radiation and wind speed and negatively correlated with air humidity.The correlation between meteorological factors and ammonia volatilization rate in late flowering stage is higher than that in fruit expansionstage.Rainfall after fertilization also affects ammonia volatilization rate.3.The relationship between ammonia volatilization accumulation and time in fertilization treatment can be expressed by Elovich kinetic equation.F test shows that the equation is very significant,and the determinant coefficient R2 ranges from 0.94 to 0.98.The relationship between ammonia volatilization accumulation and time in non-fertilization treatment is linear,and the determinant coefficient R2 ranges from 0.98 to 0.99.The higher the topdressing amount,the greater the accumulation of ammonia volatilization.The ammonia volatilization in the water storage pit fertilization treatment is mainly concentrated in the water storage pit wall,and the cumulative amount of the pit wall accounts for 72.05%?86.96%of the total accumulated amount.Under the same fertilization scheme,the cumulative amount of ammonia volatilization in ground irrigation treatment is 3.13-4.06 times of the treatment of water storage pit irrigation.The total loss rate of nitrogen in water shortage pit irrigation was 0.80%?1.61%.It shows that water storage pit irrigation can effectively reduce the loss of soil ammonia volatilization.The nitrogen loss rates of different fertilizer application schemes were as follows:one-time fertilization in late flowering stage(F1,F2)>one-time fertilization in the fruit expansion period(F3,F4)>average topdressing in the two topdressing periods(F5,F6).F5 treatment is the lowest treatment of ammonia volatilization and nitrogen loss in this test.Therefore,F5 treatment is the best treatment.Reducing the amount of topdressing and fractional application can further reduce the ammonia volatilization of orchard soil under the condition of water storage pit irrigation,which is advantageous to improve the utilization rate of nitrogen fertilizer.