Biochar has great potential as a soil conditioner and as a carrier of beneficial microorganisms that support the removal of pollutants, influence the circulation of nutrients, and support plant growth. This review summarizes and discusses factors shaping the physicochemical properties of biochar, including feedstock, pyrolysis conditions, and accompanying processes used as post-pyrolysis modification to improve the functionality of biochar. Key physical and chemical properties such as high porosity and specific surface area, nutrient content, pH, and biochar functional groups are discussed in detail to show biochar’s potential as a carrier for microorganisms. This review also discusses and summarizes biological indicators that allow for assessing the quality and efficiency of the microbiological modifiers. Finally, this paper presents the benefits and limitations of biochar application to agriculture and provides recommendations for future research to improve the quality and expand the applicability of biochar-based inoculants.

Knowledge of the effects of different organic species on soil structure and strength is gained mostly from experiments on natural soils amended with organic substances of various particle sizes, pH, ionic composition, and inorganic impurities. It greatly diversifies the experimental results and shadows individual effects of organic amendments. Therefore, to look for a clearer view, we examined the impact of HCl-washed clay-size organic species: peat, humic acids, residue after humic acid extraction, and two biochars, all derived from the same peat and having similar particles, on the structure and strength of artificial soil silt aggregates using mercury intrusion porosimetry, bulk density measurements, SEM, and uniaxial compression. Bulk density increased due to humic acid addition and decreased for the other amendments. The total pore volumes behaved oppositely. All organic substances except humic acid decreased the pore surface fractal dimension, indicating a smoothening of the pore surface. Humic acid appeared to occupy mostly the spaces between the silt grains skeleton, while the other species were also located upon silt grains. The latter effect was most evident for 600 °C heated biochar. Humic acid, peat, and the residue after humic acid extraction improved mechanical stability, whereas both biochars weakened the aggregates, which means that bulk density plays a smaller role in the mechanical stability of granular materials, as it is usually considered. A new equation relating maximum stress and the amount of the organic additives was proposed.

The most popular protein source in poultry feed mixtures is soybean. However, cheaper and more available alternative protein sources are being sought, and feed manufacturers more and more often turn their attention to the post-extraction meals of local oil plants, e.g., rapeseed. Therefore, the effect of fermented and non-fermented post-extraction rapeseed meal used as a feed additive for Japanese quails was investigated on the eggs’ quality. The study was performed on 280 females of Japanese quails fed with a mixture without rapeseed meal, with non-fermented post-extraction rapeseed meal (5%, 10% and 15%) and with fermented one (5%, 10% and 15%). During the experiment, eggs were collected from each group four times (every 4 weeks) and evaluated for their quality characteristics. The addition of 10% fermented rapeseed meal had the most beneficial effect on such eggs quality traits as egg weight, specific gravity, yolk index and color and albumen pH. However, in the majority of examined parameters, no significant differences were found between birds fed with soybean meal and those fed with fermented and non-fermented rapeseed meal (morphological elements proportions, yolk weight, albumen height and Haugh’s units, eggshell quality). This supports the thesis that the use of rapeseed meals instead of soybean meals may allow obtaining the proper quality of animal raw materials at a lower cost and with the use of local feed resources.

Knowledge on the effects of minerals on soil water stability and wettability is mostly gained from experiments on natural soils of different mineral composition. To gain a “clearer” picture, the water stability and wettability of artificial aggregates composed of soil silt and various proportions of pure minerals: kaolinite, montmorillonite, illite, zeolite and goethite, were examined. The wettability was attributed to contact angles measured goniometrically and to the water drop penetration time (WDPT). The water stability was measured by monitoring of air bubbling after aggregate immersion in water and the shrinking sphere model was used to analyse aggregates’ destruction kinetics. The rate of aggregate destruction in water increased with increasing mineral content and it slightly decreased for aggregates composed of all pure minerals except goethite. An apparent hydrophobicity period (a period where the bubbling stopped for some time), resulted most probably from the wavy shape of pores, was observed mainly for aggregates with low mineral proportions. Among all studied minerals, kaolinite increased the water contact angle and water repellency to the greatest extent. With increasing the mineral content in the aggregates up to 8%, contact angles decreased and then increased. Contact angles did not correlate with aggregates’ stability. Aggregates more rapidly penetrated by water (shorter WDPT) were destroyed faster. Water stability of aggregates containing all minerals except illite appeared to be higher for the more mechanically resistant aggregates.