Acidification of animal slurry affects the nitrogen dynamics after soil application

Abstract Slurry acidification is recommended to minimize ammonia emissions during the whole management chain. However, the impact of the application of acidified slurry to soil has been poorly studied, namely its effect on the nitrogen dynamics (organic nitrogen mineralization and nitrification). In the present study, we hypothesized that a) slurry acidification would slow down nitrification and that this effect would be comparable to that of a nitrification inhibitor (DMPP); b) the alkalinity and/or buffering capacity of some soils would neutralize the acidified slurry and minimize its effect. Thus, a laboratory incubation was run to assess the effect of pig slurry treatment by acidification or DMPP addition on N mineralization and nitrification in five contrasting soils. Our results show that slurry acidification affected the N dynamics after application to the soils, but this effect was closely related to the soil properties. The inhibitory effect of slurry acidification on nitrification was not as evident as that of the nitrification inhibitor, DMPP, but it is noteworthy that, in some soils, the nitrate content remained lower in soil amended with acidified slurry than in soil amended with slurry treated with DMPP. Furthermore, in no case did slurry acidification stimulate nitrification when compared to non-acidified slurry. It can then be concluded that slurry acidification is an efficient way to increase the NH 4 + content in slurry amended soils, without intensifying nitrification.