Reducing organic fertilizer with exogenous carbon-based fertilizers on impacts on ammonia volatilization and cucumber yield in greenhouse cropping
To address excessive ammonia emissions from agricultural sources in China,this study investigated the impact of reducing organic fertilizer application combined with exogenous carbon-based fertilizers(biochar and humic acid)on soil ammonia volatilization and cucumber yield in a greenhouse vegetable cropping system.High-throughout qPCR geochip technology was utilized to explore the microbial mechanisms influencing ammonia volatilization,aiming to identify effective measures for reducing ammonia emissions in greenhouse vegetable cropping systems.The experiment was conducted in a greenhouse vegetable cropping system in Wuqing District of Tianjin City.There were five experimental treatments:no N application(CK),recommended fertilizer application(N1,37 500 kg·hm-2 organic fertilizer),recommended fertilizer application with humic acid(N1F,37 500 kg·hm-2 organic fertilizer+2 250 kg·hm-2 humic acid),recommended fertilizer application with biochar(N1B,37 500 kg·hm-2 organic fertilizer+40 t·hm-2 biochar),and conventional fertilizer application(N2,60 000 kg·hm-2 organic fertilizer).The results revealed consistent ammonia volatilization dynamics across various fertilizer treatments,with the N2 treatment exhibiting notably higher ammonia volatilization rates.As fertilizer application intensity increased,there was a gradual increase in cumulative soil NH3 volatilization,with the order being:N2＞N1＞N1B＞N1F＞CK.By the final fruit stage,soil ammonium nitrogen content in the N2 treatment significantly surpassed that of the other treatments.Additionally,during the fruiting and late fruiting stages,soil nitrate nitrogen content in the N1,N1F,and N1B treatments was significantly higher than in the N2 treatment.Fertilizer application,particularly treatments with either biochar or humic acid,significantly increased the abundance of AOA-amoA genes.Compared to the CK treatment,both N1 and N2 exhibited a significant increase in AOA-amoA gene abundance(P＜0.05),while compared to N2 and N1,the N1F and N1B treatments demonstrated a significant elevation in AOA-amoA gene abundance(P＜0.05).Recommended fertilizer application led to an increase in the gene abundance of soil AOB-amoA,while the inclusion of humic acid or biochar had no significant effect.Mantel test results indicated that NH+4-N content,AOA-amoA,and AOB-amoA significantly affected soil ammonia volatilization in greenhouse vegetable cropping systems.Reduced fertilizer application with either biochar or humic acid could moderately reduce ammonia volatilization in greenhouse vegetable cropping systems,with humic acid demonstrating a more effective impact and effectively retaining soil mineral nitrogen.Reduced fertilizer application ensures crop yield and significantly improves nitrogen use efficiency.Considering both agronomic and environmental benefits,the recommended fertilizer application combined with humic acid(N1F)emerges as a suitable fertilization method.This study provides technical support for controlling nitrogen surface source pollution and achieving efficient nitrogen utilization in greenhouse vegetable cropping systems.
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