Effects of Long-Term Storage of Pig Slurry on Nitrogen Loss in Different Seasons and Storage Conditions

Abstract

Highlights The physicochemical properties of the pig slurry in different seasons were different, the contents of COD and total nitrogen of the pig slurry in the summer were significantly higher than the pig slurry in the other seasons. The slurry temperature varied greatly in different seasons, which affected the changes of indicators in pig slurry during long-term storage. Storing pig slurry under sealed conditions was significantly more beneficial in reducing N loss, which was 47%–56% lower than that in the open treatments. Abstract. Pig slurry (PS) can be applied to farmland only in certain periods during the year, so long-term storage is required before field application. The effects of the long-term storage of the PS on N loss in different seasons and under different storage conditions (open and sealed storage) were investigated in this study. The physicochemical properties and slurry temperature varied greatly in different seasons. The electrical conductivity, chemical oxygen demand, ammonium nitrogen, nitrate nitrogen, total nitrogen (TN), and heavy metals (Cu, Zn, Pb, As, and Cd) decreased after 150 days of storage, while the pH value increased, and all these indicators (except for the heavy metals) were affected by the slurry temperature, exhibiting a larger decrease at higher slurry temperatures. The decrease in the N loss was 47%–56% lower in the sealed treatments than in the open treatments. The As, Pb, and Cd contents of the stored PS (except for the AU-OP treatment) met the requirements specified for GB/T 40750-2021. Overall, storing PS under sealed and lower temperature conditions was conducive to reducing N loss and improving the N content of the stored PS. Keywords: Heavy metal, Nitrogen loss, Open storage, Pig slurry, Sealed storage, Temperature.