The Potential of Biochar Made from Agricultural Residues to Increase Soil Fertility and Microbial Activity: Impacts on Soils with Varying Sand Content

Abstract

Different types of soil respond variably to biochar amendment. Soil structure and fertility are properties which strongly affect the impacts of biochar on soil fertility and microbial activity. A pot experiment with lettuce was conducted to verify whether biochar amendment is more beneficial in sandy soil than in clay soil. The nutrient content (carbon and nitrogen), microbial biomass carbon, soil respiration, metabolic quotient, and plant biomass yield were determined. The treatments were prepared by mixing silty clay loam (Haplic Luvisol) with a quartz sand in ratios of 0%, 20%, 40%, 60%, 80%, and 100% of sand; the same six treatments were prepared and amended with biochar (12 treatments in total). Soil carbon and nitrogen, microbial biomass carbon, and soil respiration were indirectly dependent on the descending sand ratio, whereas the metabolic quotient increased with the ascending sand ratio. The biochar’s effects were positive for total carbon, microbial biomass carbon, metabolic quotient, and plant biomass in the sand-rich treatments. The maximum biochar-derived benefit in crop yield was found in the 100% sand + biochar treatment, which exhibited 24-fold (AGB) and 11-fold (root biomass) increases compared to the unamended treatment. The biochar application on coarse soil types with lower fertility was proven to be favorable.

Hemp biochar impacts on selected biological soil health indicators across different soil types and moisture cycles

“…Soils with lower fertility are likely to experience a higher frequency of fluctuations in the active soil microbial biomass due to lower labile C and/or available nutrients when perturbed. Our results are in line with those of [ 41 ], suggesting that biochar amendment led to higher microbial biomass response in sandy soil than in clay soil. Zhang et al [ 42 ] also found that bacterial communities in soils with lower pH values (<7) experienced significant changes but not in alkaline soils pH (>7) following the application of biochar produced from peanut shells.…”

Carbon-enriched organic amendments differently affect the soil chemical, biological properties and plant biomass in a cultivation time-dependent manner

“…Carbon enriched-manures were prepared by two methods (a) by mixing of fresh manure with HA-rich product Humac AGRO (commercial soil fertility stimulator, mined from leonardite-oxihumolite, provided by Envi Produkt Ltd., Prague, Czech Republic), and (b) by mixing of fresh manure with biochar produced from agricultural waste (cereal husks, sunflower peels and fruit processing waste) at 600 °C (Sonnenerde GmbH, Riedlingsdorf, Austria). Detailed information on the amendment has been previously published [28,29].…”

“…The soil was collected from the experimental field near the town Troubsko, Czech Republic (49°10′28"N 16°29′32"E). The soil was silty clay loam (according to USDA Textural Triangle), Haplic Luvisol (according to WRB soil classification), properties are described in detail by Brtnicky et al [29]. The topsoil was dug up to the depth of 15 cm, big parts (stones, plants residues) were removed on a 2 mm sieve, the sieved soil was then thoroughly mixed with a fine quartz sand (0.1-1.0 mm) in a weight ratio of 1:1.…”

Assessment of digestates prepared from maize, legumes, and their mixed culture as soil amendments: Effects on plant biomass and soil properties

“…The content of nutrients in the topsoil used was as follows: total carbon (TC) 7.0 g·kg −1 , total nitrogen (TN) 800 mg·kg −1 , available phosphorus (P) 485 mg·kg −1 , and available potassium (K) 0.115 mg·kg −1 . The detailed properties of the soil used can be found elsewhere ( Holatko et al., 2020 ; Brtnicky et al., 2021 ).…”

“…The content of nutrients in the topsoil used was as follows: total carbon (TC) 7.0 g•kg −1 , total nitrogen (TN) 800 mg•kg −1 , available phosphorus (P) 485 mg•kg −1 , and available potassium (K) 0.115 mg•kg −1 . The detailed properties of the soil used can be found elsewhere (Holatko et al, 2020;Brtnicky et al, 2021). The control variant was unamended, whereas digestates were applied to the other variants at a dose corresponding to 40 t•ha -1 ; see Table 2.…”