Benefits of pig manure digestate‑derived biochar on soil properties and plant growth

To assess the impact of biochar application in conjunction with synthetic and organic fertilizers on ammonia emissions, soil properties, and ryegrass growth, a two-way trial was conducted using biochar at 1.5% and 3.0% (w/w) under a controlled chambers experiment. Following a 4-week period of plant growth, various fertilizers, including urea, liquid digestate, and pelletized organic chicken manure, were distributed on the soil surface without injection. Ammonia emissions were reduced in the urea treatment with 3% and 1.5% biochar doses, whereas higher emissions were observed with liquid digestate. Notably, ammonia volatilization occurred more expeditiously (within 1 h) under the liquid digestate compared to a prolonged period of 72 h following urea application. Conversely, liquid digestate demonstrated a divergent pattern, with peak ammonia emissions occurring at 1.5% and 3.0% within 1 h. After biochar application, soil pH exhibited an elevation in the liquiddigestate and pelletized chicken manure treatments at the 3.0% biochar dose. The type of fertilizers used exerted a statistically significant impact (p ≤ 0.05) on plant green biomass. Lower biochar concentrations (1.5%) were associated with enhanced soil microbial activity, as evidenced by increased soil microbial biomass and dehydrogenase activity, irrespective of the codigested substrates. However, pelletized chicken manure exhibited heightened microbial activity at a biochar dose of 3.0%. The judicious application of biochar is paramount for reducing ammonia emissions in urea treatments, enhancing soil pH in liquid digestate and pelletized chicken manure treatments, and exerting a substantial influence on plant biomass. Thesefindings underscore the potential of biochar to augment soil microbial activity and improve soil properties, contingent upon the specific type of fertilizer utilized.