Effects Of Long-term Application Of Chlorinated Fertilizer On Nitrification And Ammonia Oxidizing Microorganisms In Brown Soil

Chlorinated fertilizers mainly refer to chemical fertilizers containing chloride ions,including potassium chloride,ammonium chloride and compound fertilizers containing potassium chloride and ammonium chloride.Some studies suggest that chlorine has an inhibitory effect on nitrification.Ammonia oxidation process is a speed-limiting step of soil nitrification,which is mainly driven by ammonia-oxidizing microorganisms and is a key link affecting soil nitrogen cycle.Therefore,this study used the long-term positioning experiment of brown soil containing chlorinated fertilizer in Shenyang Agricultural University as the platform to collect the soil samples of the main growth period and harvest period of 2018 corn,and used realtime fluorescence quantitative PCR and high-throughput sequencing technology to study the abundance and community structure of ammoxidation bacteria?AOB?,archaea?AOA?in response to chlorinated fertilizers.To Study the effects of chlorinated fertilizer on the nitrification and ammonia-oxidizing bacteria?AOB?,archaea?AOA?of brown soil in 34consecutive years,combined with soil nitrification potential,urease activity and basic chemical properties were analyzed for the effects of long-term application of chlorinated fertilizer on nitrification of brown soil and ammonia-oxidizing microorganisms.The main findings are as follows:?1?Long-term application of chlorinated fertilizer changes the p H,chloride ion and available nutrient content of the soil.In the corn seedling stage,the chloride ion content was135.8 mg/kg in the high chlorine treated soil,but did not exceed the crop chlorine tolerance threshold.After 34 years of long-term positioning,the soil p H of each treatment was lower than the soil p H before the positioning,and the p H of the soil treated with high chlorine was the largest.Chlorine treatment has little effect on the content of available P and K in soil.?2?High-chlorine treatment can inhibit soil nitrification.The nitrification potential of high-chlorine treatment was the lowest in the corn growth period.Except the harvest period,the NH₄⁺-N content in the soil at each growth stage was higher than other treatments.Low chlorine treatment had little effect on nitrification.Except for the tasseling period,the NP treatment had the highest nitrification potential and the ammonium nitrogen content was low,indicating that NP treatment promoted soil nitrification.There was no significant difference in soil nitrification between low chlorine treatment and no chlorine treatment.In corn sowing stage,seedling stage and harvest stage high chlorine treatment can inhibit soil urease activity.?3?The AOA abundance in brown soil was?1.13×10⁷—5.53×10⁷ copies/g?,which was significantly higher than that of ammonia oxidizing bacteria AOB?1.99×10⁵—1.37×10⁷copies/g?,indicating that the amount of AOA was dominant in brown soil.However,AOA and AOB jointly drive nitrification.High chlorine treatment can reduce the abundance of soil AOA and AOB.Long-term application of chlorinated fertilizer has a great influence on AOA abundance.The main factors affecting AOA are p H,chloride ion content and ammonium nitrogen content..?4?Low-chlorine treatment has little effect on the structure of a mmonia-oxidizing archaea,and high-chlorine treatment can reduce the abundance and diversity of ammonia-oxidizing archaea in brown soil.NK treatment can increase the abundance of ammonia oxidizing bacteria in the soil,while other fertilization treatments will lead to a decrease in the abundance of ammonia oxidizing bacteria.Chlorine treatment has little effect on the diversity of soil ammonia-oxidizing bacteria.In summary,long-term use of chlorinated fertilizers on brown soil,low chlorine treatment has little effect on soil AOA and AOB.High chlorine treatment can reduce the abundance of ammonia-oxidizing microorganisms and reduce the abundance and diversity of soil AOA community structure,but has little effect on soil AOB community structure.It can be seen that in brown soil,high chlorine treatment can inhibit soil nitrification and increase ammonium nitrogen content in soil by affecting the abundance of soil ammonia-oxidizing microorganisms and AOA community structure,and can inhibit soil urease activity and ensure nitrogen fertilizer.Long-term use provides a theoretical reference for rational agriculture with chlorinated fertilizer.