JWSS - Journal of Water and Soil Science

The pyrolysis of fruit trees Pruning waste to be converted to biochar with microbial inoculation is a strategy improving the biological properties in calcareous soils. In order to investigate the biochar effect on some soil biological properties of the soil in the presence of microorganisms, a factorial experiment was carried out in a completely randomized design in the rhizobox under greenhouse condition. The factors included organic matter (pruning waste biochar and control), microbial inoculation (arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria) and soil (rhizosphere and non-rhizosphere). After the end of the wheat plant growth period, microbial respiration (BR), Substrate-induced respiration (SIR), microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), acid phosphatase (ACP) and alkaline phosphatase (ALP) enzymes in the rhizosphere soil and non-rhizosphere soil were determined. The results showed that the biochar and microbial inoculation application increased BR, SIR, MBC, MBP and ALP and decreased ACP, as compared to the control. So, the highest increase in the value of BR, SIR and MBC was related to mycorrhizal inoculation with biochar. An increase of 2.67 fold of ACP activity was observed in the treatment of bacterial inoculation with Biochar, as compared to the control treatment. Also, pruning waste biochar increased the amounts of MBC, MBP and ALP by 45.62%, 56.22% and 62.6% in the rhizosphere soil rather than non-rhizosphere soil, respectively. Microbial inoculation led to the increase of 1.31 and 1.41 folds by MBP and ACP in the rhizosphere soil, as compared with non-rhizosphere soil. Bacterial inoculation in the rhizosphere soil increased the ACP enzyme activity (28.31%), as compared with non-rhizosphere soil. It could be concluded that application of biochar in the conditions of microbial inoculation improved the soil biological properties.

The present study was intended to improve the chemical properties of a saline-sodic soil using the individual application of alfalfa residue and two biochars produced from sugarcane bagasse and walnut shell, at the weighting ratio of 5%; their concomitant application with gypsum, aluminum sulfate and the mixture of these two chemical amendments was considered. The experiment was conducted in three replications using the factorial experiment in a completely randomized design. After four months of incubation, the soil samples were measured for their main chemical properties. The results showed that alfalfa residues were the most effective treatment to reduce the soil pH; so the concomitant application of this organic amendment with gypsum lowered the soil pH from 9.13 in the control (untreated soil) to 7.24. It was also observed that the addition of gypsum and/or aluminum sulfate to the soil led to the increase of the soil electrolyte concentration and consequently, the increase of soil electrical conductivity to three times greater than control, through an increase of ions, like calcium and sulfate in the soil solution. Increasing the soluble sodium concentration by replacing exchangeable sodium by other similar ions showed that the studied treatments enhanced the sodium adsorption ratio (SAR), which could be regulated by washing. Concomitant application of the walnut-shell biochar with gypsum had the most increasing effect on the soil SAR, enhancing it from 22.6 in the control to 54.3. Potassium was released from organic amendments, improving the soil general conditions; addition of chemical amendments elevated soil exchangeable potassium contents; however, the elevated soil available phosphorus contents were less influenced by chemical amendments application. As the conclusion, it seems that the positive impacts of the applied chemical and organic amendments would supplement each other; as a result, the concurrent use of both treatments not only improves the bad soil chemical properties, but also enhances the soil fertility.

Biochar as an efficient strategy for the improvement of soil properties and organic waste management may reduce the potential effects of abiotic stresses and increase soil fertility. However, the effects of this organic amendment on soil microbial indicators under combined salinity and pollution have not been studied yet. Therefore, the objective of this study was to evaluate the influence of sugarcane bagasse biochar on some soil bioindicators in a Cd-polluted soil under saline and non-saline conditions. A factorial experiment was carried out with two factors, including NaCl salinity (control, 20 and 40 mM NaCl) and sugarcane bagasse biochar (soils unamended with biochar, amended with uncharred bagasse, 400 ^oC biochar, and 600 ^oC) at 1% (w/w) using a completely randomized design. Results showed that salinity increased the mobility of Cd (12-17%), and subsequently augmented its toxicity to soil microorganisms as indicated by significant decreases in the abundance and activities of the soil microbial community. Conversely, sugarcane bagasse biochar application reduced the concentration of soil available Cd (14-18%), increased the contents of soil organic carbon (89-127%), and dissolved organic carbon (4-70%), and consequently alleviated the effect of both abiotic stresses on soil microbial community and enzyme activity. In conclusion, this experiment demonstrated that the application of sugarcane bagasse biochar could reduce the salinity-induced increases in available Cd and mitigate the interaction between salinity and Cd pollution on the measured soil bioindicators.

One of the significant factors affecting biochar properties is the pyrolysis temperature. This study aimed to investigate the effect of pyrolysis temperature on the properties and fractionation of Zn and Pb in biochars produced by sewage sludge. Biochars were prepared at temperatures of 300 to 700 °C and the physicochemical properties, availability, and fractionation of Zn and Pb were investigated. The results showed that pH, pHzpc, percentage of calcium carbonate, cation exchange capacity, specific surface area, and porosity in biochars were higher than in the feedstock. By increasing biochar production temperature, the mentioned properties increased. FT-IR revealed that the OH functional group is present in free form, either in the structure of C-OH and -COOH and aliphatic-CH2 groups in the sewage sludge. By converting sewage sludge to biochar, the intensity of these peaks decreased. In contrast, peaks representing complex aromatic structures appeared. The availability of Zn and Pb in biochar was reduced as compared to sewage sludge. The results of fractionation indicated that sewage sludge has bio-availability and toxicity of Pb and Zn. the amount of oxide and residual fractions of these two metals increased by converting sewage sludge to biochar at different temperatures. Therefore, it seems that biochar production from sewage sludge reduces the toxicity and bio-availability of Zn and Pb. Also, by incrementing the temperature of production, the bio-availability potential (bonding with organic matter), and non-toxicity (residual) of these metals increased.