Effects of ph, total solids, temperature and storage duration on gas emissions from slurry storage : A systematic review

Summary

Gaseous emissions are the main loss pathways of nutrients during dairy slurry storage. In this study, we compiled published data on cumulative ammonia (NH₃ ), nitrous oxide (N₂ O) and methane (CH₄ ) emissions from dairy slurry storage and evaluated the integrated effects of slurry pH, total solids (TS), ambient temperature (T) and length of storage (LOS) on emissions using linear mixed effects models. Results showed that the average nitrogen (N) loss by NH₃ volatilization from slurry storage was 12.5% of total nitrogen (TN), while the loss by N₂ O emissions only accounted for 0.05–0.39% of slurry TN. The NH₃ –N losses were highly related to slurry pH, lowering slurry pH leading to significant decrease of emissions. Temperature also affected NH₃ –N losses, with higher losses from slurry storage under warm conditions than cold conditions. No significant relationship was observed between NH₃ –N losses and slurry TS contents within a range from 21–169 g kg⁻¹ . The losses of N₂ O–N from dairy slurry storage were less affected by slurry pH, TS contents and temperature. The carbon (C) loss as CH₄ emissions varied from 0.01–17.2% of total carbon (TC). Emissions of CH₄ –C presented a significant positive relationship with temperature, a negative relationship with slurry TS contents and no significant relationship with slurry pH ranging from 6.6–8.6. Length of storage (more than 30 days) had no significant influence on cumulative gas emissions from slurry storage. This study provides new emission factors of NH₃, N₂ O and CH₄ in the percentage of TN or TC from dairy slurry storage. Our results indicate the potential interactive effects of slurry characteristics and storage conditions on gaseous emissions from slurry storage. Farm-scale measurements are needed to accurately estimate nutrient losses from liquid manure storage.