As the global community seeks sustainable strategies to combat climate change, incorporating C-rich materials like woody biochar (WB) into agricultural soils has gained significant attention. Biochar is essentially charcoalCharcoal is a black, brittle, and porous material produced by heating wood or other organic substances in a low-oxygen environment. It is primarily used as a fuel source for cooking and heating.   More produced from woody biomass pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More, and its stability makes it excellent for carbon sequestration. However, determining the optimal application level of this resource to maximize benefits like carbon sequestration, crop yield, and soil health has remained a critical research gap, especially in high-intensity cropping systems like red pepper farming.

A two-year field study, “Sustainable woody biochar application for improving net ecosystem carbon budget, yield and soil properties in red pepper cropping systems: a two-year field study,” published in Biochar by Sohee Yoon, Yeomyeong Lee, Hyerin An, Jasmin Melendez, and Sang Yoon Kim, provides quantitative guidance for farmers and policymakers . The researchers evaluated the overall Net Ecosystem Carbon Budget (NECB) across different WB application levels (0, 2.5, 5, and 10 Mg d.w ha⁻¹ annually) under two crop residue management scenarios. The NECB is a crucial metric that precisely estimates the balance between carbon input (from the biochar, fertilizer, and crop biomass) and carbon output (from soil respiration and biomass removal).

The study’s most significant finding is that the method of handling the crop residue post-harvest is a major factor influencing the optimal WB rate needed to achieve a positive NECB (meaning the field acts as a carbon sink).

When the entire crop biomass (shoots, roots, and fruits) was removed from the field—a common practice to facilitate successive crop production or use residues as biofuel—the optimal WB application level required to maintain a positive annual NECB was estimated to be in the range of 7.3–11.4 Mg d.w ha−1 (with a mean value of 9.4 Mg d.w ha⁻¹).

In contrast, when only the fruit was removed and the remaining crop residues (shoots and roots) were returned to the soil, the optimal WB application level dropped significantly to 1.8–6.7 Mg d.w ha⁻¹(with a mean value of 4.3 Mg d.w ha⁻¹).

This difference represents a substantial 55% reduction in the amount of WB required when residue is left on the land. This is because the incorporated residues act as an additional C input, reducing the field’s C output from harvest removal (approximately 3.7 to 7.2 Mg C ha−1 was removed in the total removal scenario). Leaving the residue, therefore, is not only an effective management practice for enhancing the C budget but also a method for saving on resource application.

Beyond the carbon budget, increasing the WB application level significantly benefited the red pepper crop itself. The highest application rate (WB10) in both years resulted in the greatest increase in total biomass productivity (shoots, roots, and fruits). Biochar incorporation increased total productivity by 19%−34% over the control treatment (WB0). Specifically, the overall fruit productivity increased by up to 18% in the first year and 16% in the second year compared to the control.

These performance increases were directly linked to improvements in soil quality. WB application effectively decreased the soil’s bulk density (improving physical properties like aeration and porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More), increased soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More (due to the biochar’s alkaline nature), and significantly raised the soil organic carbon (SOC) content by 15%−20% compared to the control (29.6–31.1 g kg−1 in the control). The enhanced fruit yield was positively correlated with soil pH and Cation Exchange Capacity (CEC).

This research provides strong, quantified support for incorporating woody biochar into red pepper cropping systems, suggesting that optimizing the application level based on residue management is a practical and highly effective strategy for sustainable agriculture and climate mitigation.

Source: Yoon, S., Lee, Y., An, H., Melendez, J., & Kim, S. Y. (2025). Sustainable woody biochar application for improving net ecosystem carbon budget, yield and soil properties in red pepper cropping systems: a two-year field study. Biochar, 7(112).