Chemical Fractions and Availability of Zn in a Calcareous Soil in Response to Biochar Amendments

Abstract

Availability of Zinc (Zn) is very low in calcareous soils and hence, an amendment must be used to increase Zn availability to plants. The main objective of this study was to assess the changes in chemical fractions and availability of Zn in a calcareous soil amended with corn residue biochar. Three corn residue biochars were produced at 200 (B200), 350 (B350), and 500°C (B500) and applied at 1 and 2% w/w to a calcareous soil with low organic C content (4.1 g kg −1) and high pH (7.7). The mixtures were incubated for 90 days in the laboratory (25 ± 2°C and 80% of soil field capacity). The application of biochar increased soil total organic carbon (TOC) (1.81-to 3.27-fold), cation exchange capacity (CEC) (1.03-to 1.14-fold) and Zn bound to organic matter (1.34-to 2.15-fold). Relative to untreated soil, the B200 biochar (1) decreased soil pH (0.22-0.30 unit); (2) increased dissolved organic carbon (DOC) (1.34-to 1.59-fold), microbial biomass carbon (MBC) (1.56-to 1.67-fold) and DTPA-extractable Zn (1.32-to 1.42-fold); and (3) maximized Zn content in 3 out of 5 soil pools, i.e., exchangeable Zn; organically bounded Zn; and Fe/ Mn-oxide-bounded Zn. In contrast, the B500 biochar (1) increased soil pH; (2) did not affect DOC or DTPA-extractable Zn quantities in soil extracts; and (3) maximized Zn content in carbonate-Zn and residual-Zn soil fractions. The B350 biochar (1) did not affect soil DOC and DTPA-extractable Zn and (2) slightly increased carbonate-Zn fractions. The effects of biochar addition on soil properties and chemical fractions of Zn were greater at 2% than 1% application rates. Results suggest that corn residue biochar produced at 200°C and applied to calcareous soils at a 2% rate may effectively increase Zn availability by increasing the amount of Zn held in the more labile Zn soil fractions.

Fe-Modified Common Reed Biochar Reduced Cadmium (Cd) Mobility and Enhanced Microbial Activity in a Contaminated Calcareous Soil

“…Ahmad et al (2014) reported that the high immobilization of PTEs in biochar-amended soils was mainly due to the presence of mineral oxides and OM in biochar, which coprecipitated and made inner-sphere complexes with PTEs. Similar to the current study, other studies indicated that biochar concentration of PTEs bounded to OM in calcareous soil increased with the addition of different biochars (Boostani et al 2019;Kabiri et al 2019;Karimi et al 2019).…”

“…The decrease in the DTPA-extractable Cd observed in the present study after the addition of biochars could be attributed to changes in Cd fractions in the soil. Soil pH strongly influences the reactions and availability of PTEs in calcareous soil (Karimi et al 2019). In comparison to the control treatment, treatments that involved the addition of biochars to soil increased the soil pH in the current study (Fig.…”

“…Overall, the results regarding the physicochemical traits and FTIR spectra of the biochars suggest that Fe-BC has a better adsorption capability than BC and perhaps more sorption sites for Cd stabilization. Soil pH was most strongly affected by biochar alkalinity (Karimi et al 2019;Tang et al 2020a). The results showed that the biochar applied to the soil in this study has a high content of alkaline ions, such as potassium (K) ( Table 2), which can neutralize the hydrogen ions in soil.…”

“…Twenty samples from different plots were collected and mixed thoroughly to obtain a composite sample. Detailed information about the study area, soil sampling process, and analysis is given in Karimi et al (2019). The soil sample was air-dried and sieved (< 2 mm).…”

Impact of Biochar on Release Kinetics of Pb (II) and Zn (II) in a Calcareous Soil Polluted with Mining Activities

“…Similarly to the present research, Karimi et al (2020) reported that the application of 2% corn residue biochar produced at 500°C decreased DTPA-Zn in a calcareous soil. In other work, Karimi et al (2019) reported that the application of corn residue biochar produced at 500°C increased Zn associated with organic matter and residual fraction in calcareous soil, while exchangeable and associated with Fe-Mn oxide fractions decreased. They reported that the application of corn residue biochar produced at 500°C increased the Zn associated with Fe-Mn oxides when compared with the control.…”