Nitrification And Nitrifying Microorganisms In Purple Paddy Soil

Nitrification, linked to the mineralization of soil biological processes which characterized nitrogen availability and subsequent nitrogen loss, is well-known and very important in soil microbial process. Considering China vast territory, there are many types of soil and their respective physical and chemical properties may lead to different nitrification activity. Soil microbes’ abundance and diversity differences also have effect on nitrification activity. Additionally, soil microbial communities and activities are influenced by environmental factors such as pH, temperature, moisture, soil ammonium nitrogen content and organic matter content, etc. Notwithstanding, farming practices has influenced on soil environment and may pose added stress which can altered the soil properties mainly the distribution of soil organic carbon and microbial activity, and create conditions for the transformation of organic matter decomposition in soil.The traditional farming methods can influence the surface soil by various conditions, thereby limiting the activity of certain microorganisms, and no-till creates soil relative stability in time and space, reduces the disturbance to the soil, can maintain and improve soil structure. Under different tillage, nitrogen transformation in rice fields has different characteristics. Under different tillage, nitrogen transformation in rice fields has different characteristics. So, studying soil microbial abundance and their role in nitrification has vital significance for understanding the soil nitrification. The development of modern molecular biology techniques enables us to study land tillage, the relationship between microbial communities and related ecological processes, particularly nitrogen cycle processes.In this paper, based on the long-term experimental field of three kinds of purple paddy soil farming methods (Conventional tillage CT, Ridge with no-tillage RNT, Flooded Paddy Field FPF) and Hechuan acid paddy field soil was used for the research analysis. The soil samples were air-dried, crushed over1mm sieve. The CK control was set and treated with2mM ammonium sulfate. Distilled water was added to adjust the moisture content to60%of water-holding capacity and incubated in the dark at28℃for4weeks. Samples were incubated in250ml petridish and each treatment has three duplicates. During incubation samples were extracted at regular interval including day-1, day-7, day-14, day-21, and day-28. The soil pH, NO3-N and NH4+-N content, exchangeable H+, exchangeable Al3+were determined, using real-time quantitative PCR to determine soil ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) of the abundance of amoA gene. The three tillage soil potential nitrification rates were calculated using the time-dependent kinetics. Study on nitrification intensity of different tillage methods showed that different tillage paddy soil nitrification intensity is different. The conventional tillage paddy soil nitrification intensity is the largest, followed by ridge with no-tillage paddy soil, and the flooded paddy field soil was the minimal. The addition of ammonium sulfate in treatments apart from the control altered the nitrification intensity in the three farming methods and in the situation of nitrogen fertilizer application was significantly improved. CT, RNT, FPF three paddy soils nitrification rate increased by1.34,1.52and1.47times respectively. Ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) amoA gene copy numbers in the three farming methods showed that CK treatment and ammonium sulfate treatment, AOA and AOB copies in the ridge tillage paddy soil was the highest, followed by conventional tillage paddy soil, and the lowest was flooded paddy field soil.In reference to different pH in the FPF soil nitrification intensity study showed that the neutral paddy soil, nitrification rate was significantly higher than the acid soil. As for the CK treatment, ammonium sulfate addition led to the neutral rice soil ammonia oxidizing archaea (AOA) amoA gene copy numbers significantly higher than the acid soil, and was10.1-13.3times in the acid paddy soil. Ammonia oxidizing bacteria (AOB) amoA gene copy numbers in acidic paddy soil was significantly higher than the neutral paddy soil, and was2.4-6.4times in the neutral paddy soil. The numbers of AOA and AOB and nitrification rates do not show a correlation.We conclude that tillage have significant impact on paddy soil nitrification, In the various tillage methods the application of nitrogen fertilizer in paddy soil nitrogen increased nitrification. Soil nitrification is strongly influenced by soil pH, the lower pH is not conducive for nitrification, In respect to the soil pH, soil nitrification in winter paddy rice soil, neutral paddy is better than acid paddy soil. Neutral AOA abundance was significantly greater than in the paddy soil acid paddy soil, however AOB abundance in acid paddy soil is significantly higher than normal paddy soil. AOA and AOB gene copy number and nitrification rate do not show correlation.