An incubation study on the stability and biological effects of pyrogenic and hydrothermal biochar in two soils

The success and feasibility of CO2-sequestration through incorporation of biochar into soils depends strongly on the long-term biochar stability and on the improvements of physical and microbial soil properties. In this study, the stability of two maize-derived biochars (from pyrolysis and hydrothermal carbonization) and of a compost-biochar mixture and their effects on microbial biomass and enzyme activity were determined in two soils during a 57-day incubation. Soil samples amended with biochar increased soil organic carbon (SOC) content by 20 or 40%. Samples amended with hydrothermal biochar showed the largest respiration rates and the largest increase in microbial and enzymatic activity compared with the untreated controls. Carbon and 13C mass balances showed that between 13 and 16% of the added hydrochar was mineralized within 8 weeks. In the arable soil, hydrochar additions greatly stimulated the degradation of SOC, thus inducing positive priming effects. The mineralization of pyrogenic biochar (pyrochar and a pyrochar-compost mixture) was significantly less (1.4–3%) and comparable to the SOC mineralization in the control soils

Carbon sequestration potential of hydrothermal carbonization char (hydrochar) in two contrasting soils; results of a 1-year field study

Soil amendment with hydrochar produced by hydrothermal carbonization of biomass is suggested as a simple, cheap, and effective method for increasing soil C. We traced C derived from corn silage hydrochar (δ13C of −13‰) added to “coarse” and “fine” textured soils (δ13C of −27‰for native soil C (SOC)) over two cropping seasons. Respiration rates increased in both soils (p<0.001) following hydrochar addition, and most of this extra respiration was derived from hydrochar C. Dissolved losses accounted for ~5 % of added hydrochar C (p<0.001). After 1 year, 33±8 % of the added hydrochar C was lost from both soils. Decomposition rates for the roughly two thirds of hydrochar that remained were very low, with half-life for less estimated at 19 years. In addition, hydrochar-amended soils preserved 15±4 % more native SOC compared to controls (negative priming). Hydrochar negatively affected plant height (p<0.01) and biomass (p<0.05) in the first but not the second crop grown on both soils. Our results confirm previous laboratory studies showing that initially, hydrochar decomposes rapidly and limits plant growth. However, the negative priming effect and persistence of added hydrochar C after 1 year highlight its soil C sequestration potential, at least on decadal timescales

Evaluation of soil sensitivity towards the irrigation with treated wastewater in the Jordan river region

An assessment of soil sensitivity was carried out regarding the soil suitability for wastewater reuse. This was done based on digital soil maps joined with spatial data on soil properties using Geographic Information Systems (GIS). Six major risks of primarily agricultural significance were defined in close collaboration with regional experts. The changes in particular soil and groundwater properties as a result of irrigation with low water quality were evaluated and discussed. Based on the local soil parameters, the specific sensitivity and suitability grades were assessed for the respective soil unit concerning irrigation with treated wastewater (TWW) using standard and specially developed methods. In conclusion, with regard to soil suitability criteria, sensitivity and suitability maps, including the aggregated total sensitivity, were presented for supporting sustainable irrigation practices