Linkage of N2O emission to functional gene abundance in an intensively managed calcareous flu-aquic soil

Liuqing Yang1, 2, Xiaotang Ju1*,Xiaojun Zhang2*

1 China Agricultural University, No.2 Yuanmingyuan Xilu, Haidian District, Beijing, China, 100193, [email protected]
2Shanghai Jiao Tong University, No.800 Dongchuan Road, Minhang District, Shanghai, China, 200240
*Author for correspondence [email protected][email protected]

Abstract

The linkage between situ N2O emissions and abundance of functional genes ammonia monooxygenase  gene (amoA), nitrate reductase gene (narG), nitrite reductase genes (nirS and nirK), N2O reductase gene (nosZ) is not well understood, impeding proposing methods for mitigation in agricultural management. Our work was focusing on this linkage. Combined traditional study method and molecular biological technique and four treatments were involved in: N0 (Zero N application, straw removal), Nopt and CNopt (Improved Nmin test, straw removal and return respectively), CM (Manure supplementary, chemical fertilizer N based on N balance calculation, straw return). Soil samples were collected on 16th April (reflect long-term N and C management effect), 9th and 14th August (reflect before and after short-term fertilization on 11st August) for biological and chemical properties analysis. We found that the amoA gene responed to short-term fertilizer while denitrification genes had no response and annual N2O emission had significant positive relationships with gene abundance mentioned above. We concluded that strong nitrification triggered by high ammonia concentration after fertilization, nitrifier denitrification or denitrification triggered by strong rainfall or irrigation in normal crop growing days without nitrogen addition were most probably responsible for N2O emissions. It is critical to reduce amoA gene function after urea-based fertilization. Meanwhile, we need to pay attention to enhanced denitrification genes functions in their favourable conditions to produce N2O when increased SOC due to long-term manure fertilization.