Fenton oxidation of biochar improves retention of cattle slurry nitrogen

Enhancing soil resilience and crop physiology with biochar application for mitigating drought stress in durum wheat (Triticumdurum)

The use of biochar has recently garnered significant attention as an agricultural management technique highly endorsed by the scientific community. Biochar, owing to its high carbon content, contributes to increased organic matter storage in the soil, consequently enhancing crop growth. This study aimed to elucidate changes in physicochemical soil fertility and durum wheat (Triticum durum) var. Vitron production under the influence of three biochar doses (0 g/kg, 5 g/kg, and 15 g/kg of soil) in combination with varying levels of drought stress (100 %, 80 %, 40 %, and 20 % of field capacity 'FC'). Notably, we observed a substantial increase in all physicochemical soil parameters, except for active calcium carbonate equivalent (ACCE), which displayed lower values (8.78 ± 1.43 %) in soils treated with biochar compared to control soil (15.69 ± 4.03 %). The biochar dose of 5 g/kg yielded the highest moisture content (8.81 %) and pH value (7.83). However, the highest organic matter content (4.89 ± 0.17 %) and total calcium carbonate equivalent 'TCCE' (3.67 ± 0.48 %) were observed with the dose 15 g/kg. Nevertheless, regarding plant growth, no improvements were observed in terms of height and above-ground biomass (AGB). Conversely, leaf surface area exhibited significant changes with biochar application, along with an increase in chlorophyll pigment content. On the other hand, drought stress significantly hindered plant height, AGB, and leaf water reserves, resulting in values of 13.48 ± 1.60 cm, 1.57 ± 0.31g/plant, and 41.79 ± 1.67 %, respectively. The interaction between biochar and water stress appeared to mitigate and limit the impact of stress. Notably, an enhancement in organic matter storage and soil water reserves was observed. For example, the moisture content in the control soil was 6.95 %, while it increased to 12.76 % for 15g biochar/kg and 80 % FC. A similar trend was observed for organic matter, TCCE, and electrical conductivity. This effect positively influenced chlorophyll a and b content, as well as leaf water content. However, when stress was combined with biochar amendment, plant height and AGB decreased. The addition of biochar improved soil fertility and physiological parameters of wheat plants. Nevertheless, when combined with water stress, especially in cases of reduced water reserves, productivity did not witness any significant improvements.

Improving nitrogen retention of cattle slurry with oxidized biochar: An incubation study with three different soils

The application of livestock slurry in soils can lead to nitrogen (N) losses through ammonia (NH₃ ) emission or nitrate (NO₃ ^- ) leaching. Oxidized biochar has great potential to mitigate N losses due to its strong adsorption capacity; however, the effects of oxidized biochar in different soils treated with slurry are currently unclear. Here, we investigated the effect of untreated and oxidized biochar (applied at a rate of 50 kg C m^-3 slurry) on reducing N losses in a laboratory experiment with three different soils (loamy sand, sandy loam, loam) amended with cattle slurry at an application rate of 73 kg N ha^-1 . Oxidized biochar reduced NH₃ emissions by 64-75% in all soils, whereas untreated biochar reduced NH₃ emissions by 61% only in the loamy sand. Oxidized biochar significantly reduced the NO₃ ^- content in the soil solution of the loamy sand in the early phase of the incubation and led to a significantly higher NO₃ ^- concentration in the same soil compared with the slurry-only treatment at the end of the experiment, indicating a significant increase in NO₃ ^- retention in this organic C-poor soil. We conclude that oxidized biochar can reduce N losses, both in the form of NH₃ emission and NO₃ ^- leaching, from cattle slurry applied to soil, particularly in soil with soil organic carbon content <1% and pH <5 (i.e., oxidized biochar can serve as a means for improving the quality of marginal and acidic soils).