Effect of cattle slurry pre-treatment by separation and addition of nitrification inhibitors on gaseous emissions and N dynamics: A laboratory study

Abstract

The application of untreated or treated animal manure to soils can result in increased N and C gaseous emissions contributing to ecosystem change and global warming. In the present study, dairy cattle slurry (liquid manure) was subjected first to pre-treatment by separation using a screw press to obtain a liquid (LF) and a solid fraction (SF). Then, the different fractions and the whole slurry (WS) were combined with two nitrification inhibitors (NI), dicyandiamide (DCD) or 3,4-dimethylpyrazole phosphate (DMPP), were applied to soil to assess the effect of slurry treatment by separation and NI addition on soil N dynamics and CH 4, CO 2, NH 3, NO and N 2O emissions. The WS and the two slurry fractions, combined or not with DCD or DMPP, were applied to soil at an equivalent field dosage of 120 kg total N ha −1. Controls including a soil only, soil–DCD and soil–DMPP treatments were also included. The mixtures were incubated for 93-d at 20 °C. Results obtained show that NI inhibited nitrification between 16 and 30-d in WS and LF, with DMPP having a longer effect over time compared to DCD. There was no significant effect of NI on nitrification for the SF treatment. Nitrification inhibitors did not significantly affect ( P > 0.05) the CH 4, CO 2 and N 2O emissions, but significantly decreased ( P < 0.05) NO emissions. Furthermore, the two NIs had a similar effect on gaseous emissions. Throughout the entire experiment, the greatest amount of NO was released from the LF treatment (without NI), while the greatest amount of N 2O was released from the SF treatment. Slurry separation had no impact on N emissions, while the combination of this process with one of the two NI led to a small reduction in total N emissions.