The Repose Of Two Typical Upland Soils Under Nitrogen Reduction And Regulation Treatments

Nitrogen is an essential element of all life,nitrogen is a key component of crop chlorophyll,and the loss of nitrogen leads to reduced yield.Environmental problems caused by excessive application of nitrogen fertilizer and low nitrogen use rates have been the main contradictions in agricultural production.The environmental pollution and damage caused by the excessive application of chemical fertilizers urgently require some control measures to reduce the use of chemical fertilizers,especially nitrogen fertilizers,while ensuring crop yields.In the process of agricultural production,many measures has been used to improve soil environment and improve soil fertility.Previous studies have indicated that biochar,straw returning,the addition of nitrification inhibitors and the spraying of foliar fertilizer play a positive role in improving soil properties and increasing yield and fattening.At the same time,a large number of studies have been carried out around nitrogen regulation,but most of the research is only about a part or a certain point of the nitrogen cycle or carbon cycle in the soil,and there is still a lack of understanding of the impact in the carbon and nitrogen cycle and related functional activities of nitrogen regulation in rhizosphere soil.In this study,two typical upland soils:acid red soil in Qujing,Yunnan,and weak alkaline Fluvo-aquic soils in Xuchang,Henan Province,respectively.Were used for field positioning experiments(starting of summer maize planting in 2016).To study the response of the functional activities of soil carbon and nitrogen cycles in the rhizosphere-bolk soil to the regulation of nitrogen,and to explore the effects of different nitrogen reduction and efficiency control measures on soil carbon and nitrogen cycling functional activities in the upland soil.The gain effect and mechanism of the control measures under nitrogen reduction conditions provide a scientific basis for optimizing farmland soil fertilization management,improving nitrogen use efficiency and reducing environmental pollution.The combination of field sample collection and laboratory analysis was used to analyze the physical and chemical properties of rhizosphere and non-rhizosphere soil,key enzymes of soil carbon and nitrogen cycle,crop yield and nitrogen use efficiency.The experimental results measured by this institute show that:(1)Analyzed the soil physicochemical properties,crop yield and nitrogen use efficiency under different control measures in wheat and com seasons respectively.Firstly,the spraying of nitrogen-fixing bacteria promoted the accumulation of DON in upland farmland;the application of nitrification inhibitor and biochar promoted the accumulation of NH4+-N in the soil.The combination of straw returning and biochar promoted the accumulation of NO3--N in the soil.Secondly,the nitrogen reduction and efficiency increase measures can achieve stable yield increase and promote the nitrogen absorption and utilization of crops.And biochar application is best.(2)Using the key enzyme activities of soil nitrogen cycle to characterize the functional characteristics of nitrogen-related microorganisms during nitrogen transformation.The results showed that proper nitrogen reduction was beneficial to the increase of soil nitrogenase activity,and the nitrogen-fixing agent spraying effect was the most significant.The application of nitrification inhibitors plays a role in inhibiting the potential nitrification rate in fluvo-aquic soils,possibly reducing the risk of nitrate loss in the fluvo-aquic soil by inhibiting the nitrification process.Under nitrogen-reducing conditions,the application of straw returning and biochar promoted the soil denitrifying enzyme activity in upland,which may increase the risk of soil N2O emission in upland farmland.The gain effect of straw returning on soil denitrifying enzyme activity is mainly reflected in com.In the season,the application of biochar is reflected in the wheat season.Nitrogenase activity and denitrifying enzyme activity in rhizosphere soil were higher than bulk soil,and the potential nitrifieation rate of rhizosphere soil was lower than that in bulk soil.(3)Soil carbon cycle-related carbohydrate decomposition enzyme activity was measured by microplate fluorescence method.The results of data analysis showed that nitrogen-fixing bacteria inhibited basal respiration of fluvo-aquic soil and had no significant effect on red soil;biochar application promoted enzyme activity of carbon cycle related enzymes in the rhizosphere soil of fluvo-aquic soil in wheat season,and the returning of straw to the soil maintained the higher enzyme activity of red soil.The activity of enzymes related to basal respiration and carbon cycle in rhizosphere soil is generally higher than that in bulk soil.