Slow pyrolysis liquid in reducing NH3 emissions from cattle slurry — Impacts on plant growth and soil organisms

A substantial percentage of manure nitrogen (N) can be lost as gaseous ammonia (NH3) during storage and field spreading. Lowering slurry pH is a simple and accepted method for preserving its N. Efficiency of slow pyrolysis liquid (PL) produced from birch (Betula sp.) as an acidifying agent, and its ability to reduce NH3 emissions following surface application of cattle slurry, was studied in a field experiment. Untreated slurry (US) and slurries acidified with PL and sulfuric acid (SA) were applied to the second harvest of a grass ley. Immediate NH3 emissions, grass biomass, N-yield and possible toxic impacts on soil nematodes and enchytraeids were examined. Furthermore, the effects on soil respiration, nitrogen dynamics and seed germination were studied in subsequent laboratory experiments. In the field, over one third of the water-extractable ammonium-N (NH4-N) applied was lost through NH3 volatilization from US. SA and PL acidified slurries reduced NH3-N emission rate equally from 3.4 to