Biomass partitioning and nutrient fluxes in Silphium perfoliatum and silage maize cropping systems.

Abstract: Cup plant cultivation as feedstock for anaerobic digestion has become an emerging topic in European Agriculture. Although there is a gap in methane yields between cup plant and the benchmark crop silage maize, cup plant as a perennial crop provides several ecological advantages. Amongst others, studies have proven its potential for carbon sequestration. With the present study, we addressed the gap in knowledge about biomass partitioning above- and belowground as well as recycling of organic matter and nutrients for cup plant and compared the results to silage maize. Therefore, a 2 year field experiment was conducted under practical conditions on rather shallow soil conditions in a low mountain landscape in Western Germany. Relevant plant fractions like litterfall, yield biomass and stubbles were collected continuously and analyzed for their nutrient contents. Results show that the cup plant is characterized by more than 2000 kg ha- 1 a- 1 of pre-harvest losses with a high palatability. In sum, only 77% of the grown cup plant biomass can be harvested in contrast to 96% of silage maize. Thus, an intense, element-specific nutrient recycling takes place in cup plant whereas this is negligible in silage maize. Furthermore, clearly different, element-specific nutrient exports with yield were highlighted. In cup plant, exports were distinctly lower for nitrogen but several times higher for calcium compared to silage maize. Cup plant also showed 36% more roots with higher root masses particularly in the subsoil. Supplementary Information: The online version contains supplementary material available at 10.1007/s10705-022-10242-0.

Long-term effects of environmentally relevant concentrations of silver nanoparticles on major soil bacterial phyla of a loamy soil.

BACKGROUND: The growing production and use of engineered AgNP in industry and private households make increasing concentrations of AgNP in the environment unavoidable. Although we already know the harmful effects of AgNP on pivotal bacterial driven soil functions, information about the impact of silver nanoparticles (AgNP) on the soil bacterial community structure is rare. Hence, the aim of this study was to reveal the long-term effects of AgNP on major soil bacterial phyla in a loamy soil. The study was conducted as a laboratory incubation experiment over a period of 1 year using a loamy soil and AgNP concentrations ranging from 0.01 to 1 mg AgNP/kg soil. Effects were quantified using the taxon-specific 16S rRNA qPCR. RESULTS: The short-term exposure of AgNP at environmentally relevant concentration of 0.01 mg AgNP/kg caused significant positive effects on Acidobacteria (44.0%), Actinobacteria (21.1%) and Bacteroidetes (14.6%), whereas beta-Proteobacteria population was minimized by 14.2% relative to the control (p ≤ 0.05). After 1 year of exposure to 0.01 mg AgNP/kg diminished Acidobacteria (p = 0.007), Bacteroidetes (p = 0.005) and beta-Proteobacteria (p = 0.000) by 14.5, 10.1 and 13.9%, respectively. Actino- and alpha-Proteobacteria were statistically unaffected by AgNP treatments after 1-year exposure. Furthermore, a statistically significant regression and correlation analysis between silver toxicity and exposure time confirmed loamy soils as a sink for silver nanoparticles and their concomitant silver ions. CONCLUSIONS: Even very low concentrations of AgNP may cause disadvantages for the autotrophic ammonia oxidation (nitrification), the organic carbon transformation and the chitin degradation in soils by exerting harmful effects on the liable bacterial phyla.

Long-term effects of environmentally relevant concentrations of silver nanoparticles on microbial biomass, enzyme activity, and functional genes involved in the nitrogen cycle of loamy soil.

The increasing production and use of engineered silver nanoparticles (AgNP) in industry and private households are leading to increased concentrations of AgNP in the environment. An ecological risk assessment of AgNP is needed, but it requires understanding the long term effects of environmentally relevant concentrations of AgNP on the soil microbiome. Hence, the aim of this study was to reveal the long-term effects of AgNP on soil microorganisms. The study was conducted as a laboratory incubation experiment over a period of one year using a loamy soil and AgNP concentrations ranging from 0.01 to 1 mg AgNP/kg soil. The short term effects of AgNP were, in general, limited. However, after one year of exposure to 0.01 mg AgNP/kg, there were significant negative effects on soil microbial biomass (quantified by extractable DNA; p = 0.000) and bacterial ammonia oxidizers (quantified by amoA gene copy numbers; p = 0.009). Furthermore, the tested AgNP concentrations significantly decreased the soil microbial biomass, the leucine aminopeptidase activity (quantified by substrate turnover; p = 0.014), and the abundance of nitrogen fixing microorganisms (quantified by nifH gene copy numbers; p = 0.001). The results of the positive control with AgNO3 revealed predominantly stronger effects due to Ag+ ion release. Thus, the increasing toxicity of AgNP during the test period may reflect the long-term release of Ag+ ions. Nevertheless, even very low concentrations of AgNP caused disadvantages for the microbial soil community, especially for nitrogen cycling, and our results confirmed the risks of releasing AgNP into the environment.

Inter and intra plant variability of enzyme profiles including various phosphoesterases and sulfatase of six wastewater treatment plants.

Biodegradation of organic wastewater constituents by activated sludge microorganisms is based on enzymatic processes. It is supposed that wastewater treatment plants (WWTP) differ in their enzymatic fingerprints. To determine such fingerprints, activated sludges from nine aerated tanks of six WWTPs were repeatedly sampled and analyzed for the activities of l-alanine aminopeptidase, esterase, α- and ß-glucosidase, alkaline phosphatase, phosphodiesterase, phosphotriesterase, and sulfatase. In one WWTP the enzymatic activities and their variations within 1 week were assayed in various process stages. Mostly the enzymatic profiles were dominated by l-alanine aminopeptidase, followed by alkaline phosphatase. They differed in variable contributions of esterase, phosphodiesterase, α- and ß-glucosidase. The sulfatase activity was generally low. For the first time phosphotriesterase activity was detected in various samples, but with limited analytical validity. Particle mass-related activities of individual enzymes varied between plants by factors 2-4 and up to 11, when related to suspension volumes.