Effects of biochar on soil nitrifying microorganisms under drip irrigation

FENG Miaomiao; LIU Jieyun; GUO Jinxiu; BIAN Yaqi; SUN Ruihan; QIU Husen

doi:10.13522/j.cnki.ggps.2025231

Abstract：[Objective]Biochar application has been reported to be capable of modifying soil physicochemical properties and microbial communities,yet its effects on nitrifying microorganisms under different irrigation conditions remain elusive.This paper investigates the combined influence of biochar addition and different irrigation methods on soil nitrifying microorganisms.[Method]The experiment was conducted in a field in northern China.It consisted of three biochar application treatments:0(CK),10(LB)and 20 t/hm2(HB),and two irrigation methods:drip irrigation(D)and conventional furrow irrigation(F).Nitrifying microorganisms in each treatment were measured using quantitative PCR(qPCR).We also measured NH4+-N and NO3--N contents,as well as gene abundances of ammonia-oxidizing archaea(AOA)and ammonia-oxidizing bacteria(AOB)in the soils.[Result]Compared with furrow irrigation,drip irrigation significantly increased AOA gene abundance and soil NO3--N content,while reducing soil NH4+-N content,indicating that optimized water and oxygen conditions under drip irrigation enhanced the activity and proliferation of nitrifying microorganisms.Under drip irrigation,biochar addition reduced AOB gene abundance and soil NH4+-N content,likely due to substrate adsorption and modification of microbial habitat.Applying 20 t/hm2 of biochar combined with drip irrigation increased NO3--N content and promoted overall nitrification,while increasing AOA abundance and reducing AOB abundance.This suggests that AOA plays the dominant role in nitrification.[Conclusion]Applying 20 t/hm2 of biochar combined with drip irrigation promotes soil nitrification primarily through enhancing the AOA population.In practice,irrigation and fertilization strategies can be adjusted to maintain nitrogen balance and optimize crop productivity.