Circular nutrient recycling via Juncus effusus-derived biochar: impacts on soil properties, sorghum yield, and GHG fluxes

Abstract

Biochar is a valuable soil amendment widely used in agriculture to improve soil health, enhance crop productivity, and strengthen climate resilience, thereby supporting sustainable farming systems. In this study, biochar derived from common rush ( Juncus effusus ) grown on the watershed was evaluated for its ability to improve soil quality, increase water retention, enhance nutrient availability, and stimulate beneficial microbial activity. The research was conducted at Prairie View A&M University (PVAMU) research farms. The study investigated the effects of this biochar on soil physical and chemical properties, sorghum production, and greenhouse gas (GHG) emissions (CO₂, N₂O, and CH₄). Treatments included half, recommended, and double-recommended application rates based on standards established by the United States Department of Agriculture (USDA). Although the double-recommended rate yielded the highest biomass and grain yield, it did not align with USDA guidelines (grain yield: 8.1–8.3 kg per 240 ft² plot compared with 4.16 kg per 240 ft² in the control). The recommended fertilizer rate performed best among the compliant treatments and improved soil moisture retention, nutrient availability, and overall soil quality (soil moisture increased by approximately 10–18%, while grain yield reached 5.9 kg per 240 ft² plot, representing about a 40% increase over the control). In contrast, chemical fertilizer alone did not provide comparable improvements in soil physical and chemical properties. The combined application of biochar and chemical fertilizer at recommended rates provided a balanced approach for supporting crop production while improving soil conditions (bulk density remained within 1.5–1.7 g cm⁻³ and nutrient concentrations increased relative to the baseline). However, because this study was conducted over a single growing season, the observed improvements in soil quality, crop productivity, and greenhouse gas dynamics should be considered preliminary. Long-term field studies are needed to validate the persistence of these effects and evaluate the sustainability of biochar application under varying environmental conditions.