Can combined compost and biochar application improve the quality of a highly weathered coastal savanna soil?

Biochar addition influences C and N dynamics during biochar co-composting and the nutrient content of the biochar co-compost

This study investigated the effects of corn cob biochar (CCB) and rice husk biochar (RHB) additions (at 0%, 5%, and 10% w/w) on nitrogen and carbon dynamics during co-composting with poultry litter, rice straw, and domestic bio-waste. The study further assessed the temperature, moisture, pH, and nutrient contents of the mature biochar co-composts, and their potential phytotoxicity effects on amaranth, cucumber, cowpea, and tomato. Biochar additions decreased NH4+-N and NO3- contents, but bacteria and fungi populations increased during the composting process. The mature biochar co-composts showed higher pH (9.0-9.7), and increased total carbon (24.7-37.6%), nitrogen (1.8-2.4%), phosphorus (6.5-8.1 g kg-1), potassium (26.8-42.5 g kg-1), calcium (25.1-49.5 g kg-1), and magnesium (4.8-7.2 g kg-1) contents compared to the compost without biochar. Germination indices (GI) recorded in all the plants tested with the different composts were greater than 60%. Regardless of the biochar additions, all composts treatments showed no or very minimal phytotoxic effects on cucumber, amaranth and cowpea seeds. We conclude that rice husk and corn cob biochar co-composts are nutrient-rich and safe soil amendment for crop production.

Selection of Suitable Organic Amendments to Balance Agricultural Economic Benefits and Carbon Sequestration

Long-term excessive use of fertilizers and intensive cultivation not only decreases soil organic carbon (SOC) and productivity, but also increases greenhouse gas emissions, which is detrimental to sustainable agricultural development. The purpose of this paper is to identify organic amendments suitable for winter wheat growth in the North China Plain by studying the effects of organic amendments on the economic benefits, carbon emissions, and carbon sequestration for winter wheat fields and to provide a theoretical basis for the wide application of organic amendments in agricultural fields. The two nitrogen rates were N0 (0 kg ha-1) and N240 (240 kg ha-1), and the four organic amendments were straw, manure, mushroom residue (M R), and biochar. The results showed that, compared to N0, N240 significantly increased the yield by 244.1-318.4% and the organic carbon storage by 16.7-30.5%, respectively, but increased the carbon emissions by 29.3-45.5%. In addition, soil carbon stocks increased with all three types of organic amendments compared to the straw amendment, with the biochar treatment being the largest, increasing carbon storage by 13.3-33.6%. In terms of yield and economic benefits, compared to the straw amendment, the manure and biochar amendments increased winter wheat yields by 0.0-1.5% and 4.0-13.3%, respectively, and M R slightly decreased wheat yield; only the economic benefit of the M R amendment was greater than that of the straw amendment, with an increase in economic benefit of 1.3% and 8.2% in the 2021-2022 and 2022-2023 seasons, respectively. Furthermore, according to the net ecosystem productivity (NEP), N0 was the source of CO2, while N240 was a sink of CO2. The TOPSIS results showed that N240 with a mushroom residue amendment could be recommended for increasing soil carbon stocks and economic benefits for winter wheat in the NCP and similar regions. Low-cost M R can increase farmer motivation and improve soil organic carbon, making a big step forward in the spread of organic materials on farmland.

Co-application of biochar and organic amendments on soil greenhouse gas emissions: A meta-analysis

Biochar has been shown to reduce soil greenhouse gas (GHG) and increase nutrient retention in soil; however, the interaction between biochar and organic amendments on GHG emissions remain largely unclear. In this study, we collected 162 two-factor observations to explore how biochar and organic amendments jointly affect soil GHG emissions. Our results showed that biochar addition significantly increased soil CO2 emission by 8.62 %, but reduced CH4 and N2O emissions by 27.0 % and 23.9 %, respectively. Meanwhile, organic amendments and the co-application with biochar resulted in an increase of global warming potential based on the 100-year time horizon (GWP100) by an average of 18.3 % and 26.1 %. More importantly, the interactive effect of biochar and organic amendments on CO2 emission was antagonistic (the combined effect was weaker than the sum of their individual effects), while additive on CH4 and N2O emissions. Additionally, our results suggested that when biochar is co-applied with organic amendments, soil GHG emissions were largely influenced by soil initial total carbon, soil texture, and biochar feedstocks. Our work highlights the important interactive effects of biochar and organic amendments on soil GHG emissions, and provides new insights for promoting ecosystem sustainability as well as mitigating future climate change.

Pyrolysis Temperature vs. Application Rate of Biochar Amendments: Impacts on Soil Microbiota and Metribuzin Degradation

Biochar-amended soils influence the degradation of herbicides depending on the pyrolysis temperature, application rate, and feedstock used. The objective of this study was to evaluate the influence of sugarcane straw biochar (BC) produced at different pyrolysis temperatures (350 °C, 550 °C, and 750 °C) and application rates in soil (0, 0.1, 0.5, 1, 1.5, 5, and 10% w/w) on metribuzin degradation and soil microbiota. Detection analysis of metribuzin in the soil to find time for 50% and 90% metribuzin degradation (DT₅₀ and DT₉₀) was performed using high-performance liquid chromatography (HPLC). Soil microbiota was analyzed by respiration rate (C-CO₂), microbial biomass carbon (MBC), and metabolic quotient (qCO₂). BC350 °C-amended soil at 10% increased the DT₅₀ of metribuzin from 7.35 days to 17.32 days compared to the unamended soil. Lower application rates (0.1% to 1.5%) of BC550 °C and BC750 °C decreased the DT₅₀ of metribuzin to ~4.05 and ~5.41 days, respectively. BC350 °C-amended soil at high application rates (5% and 10%) provided high C-CO₂, low MBC fixation, and high qCO₂. The addition of low application rates (0.1% to 1.5%) of sugarcane straw biochar produced at high temperatures (BC550 °C and BC750 °C) resulted in increased metribuzin degradation and may influence the residual effect of the herbicide and weed control efficiency.

The current status and challenges of biomass biorefineries in Africa: A critical review and future perspectives for bioeconomy development

Africa benefits from diverse biomasses that are rich in high-added value materials and precursors for energy, food, agricultural, cosmetic and medicinal applications. Many African countries are interested in valorizing biomasses to develop efficient and integrated biorefinery processes and their use for local and regional economic development. Thus, this report critically reviews the current status of African biomass richness, its diversity, and potential applications. Moreover, particular attention is given to bioenergy production, mainly by biological and thermochemical conversion processes. This also includes biomass valorization in agriculture, particularly for the production of plant-based biostimulants, which are a potential emerging agri-input sector worldwide. This study points out that even though several processes for biofuel, biogas, biofertilizer and biostimulant production have already been established in Africa, their development on a larger scale remains limited. This study also reports the different socioeconomic and political aspects of biomass applications, along with their challenges, opportunities, and future research perspectives, to promote concrete technologies transferable into an industrial level.

Biochar/vermicompost promotes Hybrid Pennisetum plant growth and soil enzyme activity in saline soils

Soil salinity has become a major threat to land degradation worldwide. The application of organic amendments is a promising alternative to restore salt-degraded soils and alleviate the deleterious effects of soil salt ions on crop growth and productivity. The aim of present study was to explore the potential impact of biochar and vermicompost, applied individually or in combination, on soil enzyme activity and the growth, yield and quality of Hybrid Pennisetum plants suffered moderate salt stress (5.0 g kg^-1 NaCl in the soil). Our results showed that biochar and/or vermicompost promoted Na⁺ exclusion and K⁺ accumulation, relieved stomatal limitation, increased leaf pigment contents, enhanced electron transport efficiency and net photosynthesis, improved root activity, and minimized the oxidative damage in Hybrid Pennisetum caused by soil salinity stress. In addition, soil enzymes were also activated by biochar and vermicompost. These amendments increased the biomass and crude protein content, and decreased the acid detergent fiber and neutral detergent fiber contents in salt-stressed Hybrid Pennisetum. Biochar and vermicompost addition increased the biomass and quality of Hybrid Pennisetum due to the direct effects related to plant growth parameters and the indirect effects via soil enzyme activity. Finally, among the different treatments, the use of vermicompost showed better results than biochar alone or the biochar-compost combination did, suggesting that the addition of vermicompost to the soil is an effective and valuable method for reclamation of salt-affected soils.

Revamping highly weathered soils in the tropics with biochar application: What we know and what is needed

Fast weathering of parent materials and rapid mineralization of organic matter because of prevalent climatic conditions, and subsequent development of acidity and loss/exhaustion of nutrient elements due to intensive agricultural practices have resulted in the degradation of soil fertility and productivity in the vast tropical areas of the world. There is an urgent need for rejuvenation of weathered tropical soils to improve crop productivity and sustainability. For this purpose, biochar has been found to be more effective than other organic soil amendments due to biochar's stability in soil, and thus can extend the benefits over long duration. This review synthesizes information concerning the present status of biochar application in highly weathered tropical soils highlighting promising application strategies for improving resource use efficiency in terms of economic feasibility. In this respect, biochar has been found to improve crop productivity and soil quality consistently through liming and fertilization effects in low pH and infertile soils under low-input conditions typical of weathered tropical soils. This paper identifies several advance strategies that can maximize the effectiveness of biochar application in weathered tropical soils. However, strategies for the reduction of costs of biochar production and application to increase the material's use efficiency need future development. At the same time, policy decision by linking economic benefits with social and environmental issues is necessary for successful implementation of biochar technology in weathered tropical soils. This review recommends that advanced biochar strategies hold potential for sustaining soil quality and agricultural productivity in tropical soils.

Bioaccumulation and Mass Balance Analysis of Veterinary Antibiotics in an Agricultural Environment

Veterinary antibiotics (VAs) released into the environment are a concern because of the possibility for increasing antibiotic-resistance genes. The concentrations of six VAs, chlortetracycline, oxytetracycline, tetracycline, sulfamethazine, sulfamethoxazole, and sulfathiazole, in manure-based compost, soil, and crops were measured using liquid chromatography–tandem mass spectrometry. Mass balance analysis was conducted based on the measured antibiotic concentration, cultivation area, and amount of manure-based compost applied. The result showed that the detected mean concentration of VAs ranges was 3.52~234.19 μg/kg, 0.52~13.08 μg/kg, and 1.05~39.57 μg/kg in manure-based compost, soil, and crops, respectively, and the substance of VAs detected in different media was also varied. Mass balance analysis showed that the VAs released from the manure-based compost can remain in soil (at rates of 26% to 100%), be taken up by crops (at rates of 0.4% to 3.7%), or dissipated (at rates of 9% to 73%) during the cultivation period. Among the six VAs, chlortetracycline and oxytetracycline mainly remained in the soil, whereas sulfamethoxazole and sulfathiazole were mainly dissipated. Although we did not verify the exact mechanism of the fate and distribution of VAs in this study, our results showed that these can vary depending on the different characteristics of VAs and the soil properties.