Showing papers by "Karin Müller published in 2018"

Effects of biochar application in forest ecosystems on soil properties and greenhouse gas emissions: a review

Abstract: Forests play a critical role in terrestrial ecosystem carbon cycling and the mitigation of global climate change. Intensive forest management and global climate change have had negative impacts on the quality of forest soils via soil acidification, reduction of soil organic carbon content, deterioration of soil biological properties, and reduction of soil biodiversity. The role of biochar in improving soil properties and the mitigation of greenhouse gas (GHG) emissions has been extensively documented in agricultural soils, while the effect of biochar application on forest soils remains poorly understood. Here, we review and summarize the available literature on the effects of biochar on soil properties and GHG emissions in forest soils. This review focuses on (1) the effect of biochar application on soil physical, chemical, and microbial properties in forest ecosystems; (2) the effect of biochar application on soil GHG emissions in forest ecosystems; and (3) knowledge gaps concerning the effect of biochar application on biogeochemical and ecological processes in forest soils. Biochar application to forests generally increases soil porosity, soil moisture retention, and aggregate stability while reducing soil bulk density. In addition, it typically enhances soil chemical properties including pH, organic carbon stock, cation exchange capacity, and the concentration of available phosphorous and potassium. Further, biochar application alters microbial community structure in forest soils, while the increase of soil microbial biomass is only a short-term effect of biochar application. Biochar effects on GHG emissions have been shown to be variable as reflected in significantly decreasing soil N2O emissions, increasing soil CH4 uptake, and complex (negative, positive, or negligible) changes of soil CO2 emissions. Moreover, all of the aforementioned effects are biochar-, soil-, and plant-specific. The application of biochars to forest soils generally results in the improvement of soil physical, chemical, and microbial properties while also mitigating soil GHG emissions. Therefore, we propose that the application of biochar in forest soils has considerable advantages, and this is especially true for plantation soils with low fertility.

Characterization of pig manure-derived hydrochars for their potential application as fertilizer.

Abstract: In China, intensive pig farming has led to serious environmental issues with the need to dispose off large quantities of pig manure. Chinese agriculture relies on high inputs of chemical fertilizers leading to gradual decreasing organic matter contents in many arable soils. We propose that hydrochars produced from pig manure could potentially replace chemical fertilizers and, at the same time, resolve the waste disposal problem. The hydrochars used in this study were produced from pig manure at five different pyrolysis temperatures ranging between 160 and 240 °C and three residence times (1, 5, and 8 h). All hydrochars were assessed for composition of major elements. Results showed that the yield and organic matter (OM) contents in hydrochars were 50–74% and 40–56%, respectively. The concentrations of total nitrogen (N), potassium (K2O), and OM in the hydrochar decreased, whereas contents of phosphorus (P2O5), copper (Cu), and zinc (Zn) increased with increasing reaction temperature and time. Hydrothermal carbonization of pig manure is a rapid method for transforming pig manure into an organic fertilizer, but it is necessary to assess the potential soil contamination risk of Cu and Zn for the pig manure hydrochar as organic fertilizer.

Glyphosate application increased catabolic activity of gram-negative bacteria but impaired soil fungal community

Abstract: Glyphosate is a non-selective organophosphate herbicide that is widely used in agriculture, but its effects on soil microbial communities are highly variable and often contradictory, especially for high dose applications. We applied glyphosate at two rates: the recommended rate of 50 mg active ingredient kg−1 soil and 10-fold this rate to simulate multiple glyphosate applications during a growing season. After 6 months, we investigated the effects on the composition of soil microbial community, the catabolic activity and the genetic diversity of the bacterial community using phospholipid fatty acids (PLFAs), community level catabolic profiles (CLCPs), and 16S rRNA denaturing gradient gel electrophoresis (DGGE). Microbial biomass carbon (Cmic) was reduced by 45%, and the numbers of the cultivable bacteria and fungi were decreased by 84 and 63%, respectively, under the higher glyphosate application rate. According to the PLFA analysis, the fungal biomass was reduced by 29% under both application rates. However, the CLCPs showed that the catabolic activity of the gram-negative (G−) bacterial community was significantly increased under the high glyphosate application rate. Furthermore, the DGGE analysis indicated that the bacterial community in the soil that had received the high glyphosate application rate was dominated by G− bacteria. Real-time PCR results suggested that copies of the glyphosate tolerance gene (EPSPS) increased significantly in the treatment with the high glyphosate application rate. Our results indicated that fungi were impaired through glyphosate while G− bacteria played an important role in the tolerance of microbiota to glyphosate applications.

Using Biochar for Remediation of Contaminated Soils

Abstract: In recent years, soil contamination has become a global environmental problem. Biochar is a porous and carbon-rich material produced from pyrolysis of biomass residues from agricultural and forestry production. It can be used to immobilize heavy metals and organic pollutants in soil through adsorption. Here we report results obtained from our recent studies focusing on the interactions between biochar and soil contaminants. Incubation and pot experiments were carried out to investigate the effect of biochar type, application rate, and particle size on soil properties, bioavailability, mobility, and redistribution of the heavy metals in soil and the accumulation of heavy metals in the plants. Batch equilibration method was used to explore the effect of biochar type, aging process, dosage, and soil organic carbon content on adsorption and desorption of organic pollutants (e.g., phthalic acid esters, or PAEs) in soil. Incubation and pot trials were conducted to evaluate the impact of biochar on the degradation and bioavailability of PAEs in soils. Our results demonstrate that biochar can potentially be used as soil amendment for remediation of soils contaminated with heavy metals and organic pollutants. The efficacy of biochar application on immobilization of contaminants varies with the type, application rate, and particle size of biochars, soil properties, and contaminant types.