Short-Term Effects of Biogas Digestates and Pig Slurry Application on Soil Microbial Activity

Abstract

The effect of four biogas digestates (BD-A, BD-B, BD-C, and BD-D) and pig slurry (PS) on soil microbial functions was assessed at application rates corresponding to 0-1120 kg NH 4 + -N ha −1 . At dose corresponding to 140 kg NH 4 + -N ha −1 , 30.9-32.5% of the carbon applied in BD-A, BD-C, and PS was utilized during 12 days, while for BD-B and BD-D corresponding utilization was 19.0 and 16.9%, respectively. All BDs resulted in net nitrogen assimilation at low rates (17.5-140 kg NH 4 + -N ha −1 ) but net mineralization dominated at higher rates. PS resulted in net mineralization at all application rates. All residues inhibited potential ammonium oxidation (PAO), with EC 50 -values ranging between 45 and 302 kg NH 4 + -N ha −1 . Low rates of BDs appeared to weakly stimulate potential denitrification activity (PDA), while higher rates resulted in logarithmic decrease. The EC 50 -values for PDA were between 238 and 347 kg NH 4 + -N ha −1 . No inhibition of PDA was observed after amendment with PS. In conclusion, biogas digestates inhibited ammonia oxidation and denitrification, which could be an early warning of potential hazardous substances in the digestates. However, this effect can also be regarded as positive, since it may reduce nitrogen losses.

Root Biomass Distribution of Populus sibirica and Ulmus pumila Afforestation Stands Is Affected by Watering Regimes and Fertilization in the Mongolian Semi-arid Steppe

“…The sheep manure compost that was used in the present work might be compared to unmatured compost characterized by a high concentration of ammonium, organic acids, and other compounds that can be phytotoxic and inhibit root growth (Zucconi et al, 1981b;Chanyasak et al, 1983a,b;Wong, 1985). Although these chemicals do not induce lasting toxic effects in the environment (Zucconi et al, 1981a), long-term effects can occur from unstabilized organic material due to ammonium immobilization by soil microorganism, which makes it unavailable for plant utilization resulting in deficiency problems (Bengston and Cornette, 1973;Terman et al, 1973;Busby et al, 2007;Alburquerque et al, 2012;Abubaker et al, 2015). Furthermore, the low performance of digested manure might be due to the increased concentration of NH + 4 (Risberg et al, 2017), which can be lost to the atmosphere by volatilization especially from sandy soil (Ni et al, 2012) and has been generally related to a decrease of root growth (Zhang et al, 2017), or more specifically to the inhibition of the primary root elongation, root biomass (Tian et al, 2008;Giehl and von Wiren, 2014;Morris et al, 2017;Abubaker et al, 2020), and deep roots development (Comfort et al, 1988).…”

Agronomic characteristics of five different urban waste digestates

“…FW3 digestate did not show notable differences in ryegrass growth experiments, indicating that the increase of mineralized N in soil was not vital for plant growth (Gunnarsson et al, 2010), when the initial NH 4 -N concentration was high. In addition, the low mineralization can be attributed to the availability of organic nitrogen (Abubaker et al, 2015, Rigby & Smith, 2013, which was low due to the variation in the digestate application volumes.…”

The Chemical Composition of Biogas Digestates Determines Their Effect on Soil Microbial Activity

“…The comparison of biogas digestates and fly ash also showed the beneficial effects of digestates on soil microbial activity and biomass [11,12]. But even though those results suggest a positive impact on microbial activity, some also indicate a potential inhibitory effect [13,14] or report only a short-lived rise in microbial activity, followed by a drop to initial levels [15,16]. Furthermore, most of these studies have only a limited explanatory power because they were either done with a very limited number of digestates and/or only under controlled conditions.…”