Effects of artificial simulated acidification on soil nitrification in greenhouse

Purpose A large amount of nitrate leaching produced by nitrification during vegetable production can lead to soil acidification in greenhouse system. It is of great significance to clarify the nitrification and its microbial mechanism in acidification soil.Materials and Methods Simulated acidification experiment with artificially manipulated pH gradients (T1: pH 7.0, T2: pH 6.5, T3: pH 6.0, T4: pH 5.5, T5: pH 4.5) was conducted in a tomato potted experiment in the greenhouse. The abundance and community structure of ammonia oxidizers under different pH gradients were analyzed by q-PCR and high-throughput sequencing methods, respectively.Results and discussions Soil acidification led to a decrease in soil organic matter (SOM), total nitrogen (TN), NH3 concentration and enzyme activities. The abundance of ammonia-oxidizing archaea (AOA) in soil was higher than that of ammonia oxidizing bacteria (AOB) in pH ranged from 6.93 to 5.33, and the opposite trend was observed when soil pH was 4.21. In acidification soils, the dominant strain in AOB was Nitrosospira, while the dominant AOA strain was Nitrososphaera. Soil pH, NH4+ content, and microbial biomass were the key factors shaping the abundance and community structure of ammonia oxidizers. Soil nitrification activity (PNA) was correlated with both AOA and AOB, with the composition of AOA was the most important factor affecting PNA.Conclusions PNA was co-dominated by AOA and AOB in simulated acidification soils. Changes of soil pH, NH4+ and microbial biomass caused by acidification were the main factors for the differences of ammonia oxidizing microbial community in greenhouse soils.