Effective Strategies for Controlling Ammonia Volatilisation Under the Mode of Replacing Chemical Fertilisers With Biogas Slurry

ABSTRACT

Biogas slurry can effectively replace chemical nitrogen fertilisers by drip irrigation, but its high ammonia nitrogen content leads to ammonia volatilisation. This study investigated the effects of drip irrigation methods (surface vs. subsurface) and biogas slurry substitution ratios (0%, 50%, 100%) on ammonia volatilisation using controlled indoor soil column experiments. Ammonia volatilisation was quantified by the ammonia absorption method, and the NH ₃ ‐derived indirect global warming potential (GWP) resulting from ammonia volatilisation was evaluated. The results revealed that as the biogas slurry substitution ratio increased, the ammonia volatilisation also increased. Compared with surface drip irrigation with complete substitution, the 25‐ and 40‐cm subsurface drip irrigation treatments markedly reduced cumulative NH3 volatilisation, with the NH ₃ ‐derived indirect GWP decreasing from 117 to approximately 59 kg CO ₂ ‐eq ha ⁻¹ , corresponding to an approximately 50% reduction. However, different burial depth treatments resulted in similar total ammonia volatilisation amounts over time. Taking into account both gas emissions and biogas slurry utilisation, it is recommended to adopt a shallow burial depth of 25 cm in combination with complete substitution of biogas slurry for chemical fertilisers as an effective strategy for controlling ammonia gas volatilisation in biogas slurry drip irrigation systems.