The Fate of Sulfate in Acidified Pig Slurry during Storage and Following Application to Cropped Soil

Abstract

Acidification of slurry with sulfuric acid is a recent agricultural practice that may serve a double purpose: reducing ammonia emission and ensuring crop sulfur sufficiency. We investigated S transformations in untreated and acidified pig slurry stored for up to 11 mo at 2, 10, or 20 degrees C. Furthermore, the fertilizer efficiency of sulfuric acid in acidified slurry was investigated in a pot experiment with spring barley. The sulfate content from acidification with sulfuric acid was relatively stable and even after 11 mo of storage the majority was in the plant-available sulfate form. Microbial sulfate reduction during storage of acidified pig slurry was limited, presumably due to initial pH effects and a limitation in the availability of easily degradable organic matter. Sulfide accumulation was observed during storage but the sulfide levels in acidified slurry did not exceed those of the untreated slurry for several months after addition. The S fertilizer value of the acidified slurry was considerable as a result of the stable sulfate pool during storage. The high content of inorganic S in the acidified slurry may potentially lead to development of odorous volatile sulfur-containing compounds and investigations are needed into the relationship between odor development and the C and S composition of the slurry.

Effects of Acidifying Pig Diets on Emissions of Ammonia, Methane, and Sulfur from Slurry during Storage

“…However, the absolute levels were low compared with previous investigations regarding total S content (Eriksen et al, 1995) and S emissions (Eriksen et al, 2008). An initial level of total S of 200 mg S g -1 may therefore indicate that the dietary ingredients, as well as the diets, did not contain excessive levels of S.…”

“…It has been found that acidification of slurry to pH 5.5 inhibits sulfate reduction (Eriksen et al, 2008Ottosen et al, 2009). Contrary to these observations, the dietary acidification in this experiment of 0.4 to 0.6 pH units did not appear to influence sulfate reduction (Fig.…”

Alternatives to sulfuric acid for slurry acidification: impact on slurry composition and ammonia emissions during storage

“…This treatment is currently performed at the farm scale in Denmark by addition of concentrated sulfuric acid (H 2 SO 4 ). The use of this additive is mainly governed by economic reasons since H 2 SO 4 is one of the cheaper acids available (Eriksen et al, 2008). In Denmark this practice has notably increased in recent years (Birkmose and Vestergaard, 2013) as the Danish legislation recommends this treatment to reduce NH 3 emissions (Hoeve et al, 2016).…”

Transport of Cryptosporidium parvum Oocysts in Soil Columns following Applications of Raw and Separated Liquid Slurries

“…Application of animal slurry to agricultural land is practiced worldwide to fertilize the soil and increase the organic matter content (11). At the same time, animal slurry is also a well-documented source of different pathogens such as Cryptosporidium spp.…”

“…that may be released into the environment. Conventional slurry management leads to nutrient losses both during storage and when applied to the fields (11,40), and the slurry has an obnoxious smell. By separating the slurry mechanically as well as chemically into a solid fraction that is typically composted before use and a liquid fraction used to fertilize the paddocks, nutrient losses and smell problems are reduced (12).…”