The fate of fertilizer nitrogen in a high nitrate accumulated agricultural soil.

Zhi Quan,Bin Huang,Haiyang Zhang,Yi Shi,Caiyan Lu,Yunting Fang,Xin Chen

doi:10.1038/srep21539

Zhi Quan, Bin Huang + Show 5 more

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https://doi.org/10.1038/srep21539

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Abstract

Well-acclimatized nitrifiers in high-nitrate agricultural soils can quickly nitrify NH4+ into NO3− subject to leaching and denitrifying loss. A 120-day incubation experiment was conducted using a greenhouse soil to explore the fates of applied fertilizer N entering into seven soil N pools and to examine if green manure (as ryegrass) co-application can increase immobilization of the applied N into relatively stable N pools and thereby reduce NO3− accumulation and loss. We found that 87–92% of the applied 15N-labelled NH4+ was rapidly recovered as NO3− since day 3 and only 2–4% as microbial biomass and soil organic matter (SOM), while ryegrass co-application significantly decreased its recovery as NO3− but enhanced its recovery as SOM (17%) at the end of incubation. The trade-off relationship between 15N recoveries in microbial biomass and SOM indicated that ryegrass co-application stabilized newly immobilized N via initial microbial uptake and later breakdown. Nevertheless, ryegrass application didn’t decrease soil total NO3− accumulation due to its own decay. Our results suggest that green manure co-application can increase immobilization of applied N into stable organic N via microbial turnover, but the quantity and quality of green manure should be well considered to reduce N release from itself.

Highlights

Well-acclimatized nitrifiers in high-nitrate agricultural soils can quickly nitrify NH4+ into NO3− subject to leaching and denitrifying loss
High nitrification potential and low NO3− immobilization are responsible for NO3− accumulation in agricultural soils[7]
Our results show that the studied greenhouse soil is characterized by high NO3− accumulation

Summary

Introduction

Well-acclimatized nitrifiers in high-nitrate agricultural soils can quickly nitrify NH4+ into NO3− subject to leaching and denitrifying loss. A 120-day incubation experiment was conducted using a greenhouse soil to explore the fates of applied fertilizer N entering into seven soil N pools and to examine if green manure (as ryegrass) co-application can increase immobilization of the applied N into relatively stable N pools and thereby reduce NO3− accumulation and loss. Long-term N fertilization and tillage greatly increase the population and alter the community structure of ammonia oxidizing bacteria, as well as the nitrification capacity[4,8,9,10] This is confirmed by the significant positively relationship between nitrification potential and soil NO3− content[7,11]. Co-application of N fertilizer with organic materials is especially common in high-input cropping systems, and it is considered to be a good agronomic practice as it is thought to elevate microbial bioavailability of the applied N and reduce N loss to the environment[12]. Previous studies on the fate of soil added 15N mainly focused on its transformation to www.nature.com/scientificreports/

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