Successful outcome of phytostabilization in Cr(VI) contaminated soils amended with alkalizing additives

This study analysed the effect of three alkalizing soil amendments (limestone, dolomite chalcedonite) on aided phytostabilization with Festuca rubra L. depending on the hexavalent chromium (Cr(VI)) level in contaminated soil. Four different levels of Cr(VI) were added to the soil (0, 50, 100 and 150 mg/kg). The Cr contents in the plant roots and above-ground parts and the soil (total and extracted Cr by 0.01 M CaCl2) were determined with flame atomic absorption spectrometry. The phytotoxicity of the soil was also determined. Soil amended with chalcedonite significantly increased F. rubra biomass. Chalcedonite and limestone favored a considerable accumulation of Cr in the roots. The application of dolomite and limestone to soil contaminated with Cr(VI) contributed to a significant increase in pH values and was found to be the most effective in reducing total Cr and CaCl2-extracted Cr contents from the soil. F. rubra in combination with a chalcedonite amendment appears to be a promising solution for phytostabilization of Cr(VI)-contaminated areas. The use of this model can contribute to reducing human exposure to Cr(VI) and its associated health risks. © 2020 by the authors.Ministerstwo Nauki i Szkolnictwa Wyższego: MNiS

Long-Term Effects of Biochar-Based Organic Amendments on Soil Microbial Parameters

Biochar application to the soil has been recommended as a carbon (C) management approach to sequester C and improve soil quality. Three-year experiments were conducted to investigate the interactive effects of three types of amendments on microbial biomass carbon, soil dehydrogenase activity and soil microbial community abundance in luvisols of arable land in the Czech Republic. Four different treatments were studied, which were, only NPK as a control, NPK + cattle manure, NPK + biochar and NPK + combination of manure with biochar. The results demonstrate that all amendments were effective in increasing the fungal and bacterial biomass, as is evident from the increased values of bacterial and fungal phospholipid fatty acid analysis. The ammonia-oxidizing bacteria population increases with the application of biochar, and it reaches its maximum value when biochar is applied in combination with manure. The overall results suggest that co-application of biochar with manure changes soil properties in favor of increased microbial biomass. It was confirmed that the application of biochar might increase or decrease soil activity, but its addition, along with manure, always promotes microbial abundance and their activity. The obtained results can be used in the planning and execution of the biochar-based soil amendments

Humic Acid Mitigates the Negative Effects of High Rates of Biochar Application on Microbial Activity

Objective: Biochar and a commercial humic acid-rich product, Humac (modified leonardite), represent soil amendments with the broad and beneficial effects on various soil properties. Their combination has been scarcely tested so far, although the positive impact of their interaction might be desirable. Materials and Methods: The dehydrogenase activity (DHA), microbial biomass carbon (Cmic), soil respiration (basal and substrate-induced), enzyme activities, total carbon (Ctot), and both shoot and root biomass yield were measured and compared in the short-term pot experiment with the lettuce seedlings. The following treatments were tested: the unamended soil (control), the Humac-amended soil (0.8 g·kg−1), the biochar-amended soil (low biochar 32 g·kg−1, high biochar 80 g·kg−1), and the soil-amended with biochar + Humac. Results: The effect of both amendments on the soil pH was insignificant. The highest average values of Ctot and Cmic were detected in high biochar treatment and the highest average values of basal and substrate-induced respiration (glucose, glucosamine, alanine) were detected in the low biochar treatment. The phosphatase activity and fresh and dry lettuce aboveground biomass were the highest in the low biochar + Humac treatment. Conclusions: Even though the combination of both biochar + Humac decreased the microbial activities in the amended soil (Cmic, DHA, enzymes, substrate-induced respiration) at the low biochar dose, they mitigated the detrimental effect of the high biochar dose on respiration (all the types) and the enzyme (phosphatase, arylsulphatase) activities. In contrast to the previously published research in this issue, the effects could not be attributed to the change of the soil pH