Coffee waste as an eco-friendly and low-cost alternative for biochar production impacts on sandy soil chemical attributes and microbial gene abundance

ABSTRACT Biochar is a material produced by the pyrolysis of agro-industrial waste, which has become one of the most promising management tools to improve soil quality. The aim was to determine the effects of incorporating biochar from different coffee wastes in sandy soil, cropped with maize, on soil chemical and microbial attributes. The experiment followed a factorial design 2 × 3 + 1 with two types of biochar, including coffee ground (CG) or coffee husk (CH) in 3 doses (4, 8, and 16 t·ha-1) and a control fertilized solely with bovine manure (3 t·ha-1). The variables analyzed were soil organic carbon, chemical attributes, microbial biomass (C, N and P), soil basal respiration and microbial gene abundance (16S rRNA, 18S rRNA and nifH gene). Most chemical attributes were strongly increased by CH application, while CG at 8 t·ha-1 increased the soil C:N ratio (3.5 times), P (2.1 times) and K+ (7.9 times) and at 4 t·ha-1 increased the C content, microbial biomass C and N (3, 2.1 and 1.6 times, respectively). The application of CG biochar at 16 t·ha-1 showed trend to increase the abundance of bacteria, fungi and diazotrophic genes (11, 10 and 2%, respectively). Contribution of both coffee biochar types, but mainly CH, was more effective than the soil that received organic manure alone. Biochar from coffee wastes is a promising tool to improve sandy soil quality.

【摘要】 生物炭（Biochar）是经农工业废弃物热解制备的材料，现已成为提升土壤质量最具潜力的管理手段之一。本研究旨在明确：将不同咖啡废弃物来源的生物炭施用于种植玉米的砂质土壤后，对土壤化学与微生物属性的影响。实验采用2×3+1因子设计，设置2种生物炭类型——咖啡渣（CG）与咖啡壳（CH），3种施用量（4、8、16 t·ha⁻¹），并设置仅施用3 t·ha⁻¹牛粪肥的对照组。本次研究测定的指标包括：土壤有机碳、土壤化学属性、微生物生物量（碳、氮、磷）、土壤基础呼吸以及微生物基因丰度（16S rRNA、18S rRNA与nifH基因）。研究结果表明，咖啡壳生物炭（CH）施用后可显著提升多数土壤化学属性；咖啡渣生物炭（CG）在施用量为8 t·ha⁻¹时，可使土壤C:N比提升3.5倍、磷含量提升2.1倍、钾离子提升7.9倍；在施用量为4 t·ha⁻¹时，可提升土壤碳含量、微生物生物量碳与氮（分别为原水平的3、2.1与1.6倍）。当CG生物炭施用量为16 t·ha⁻¹时，细菌、真菌与固氮菌基因丰度呈现上升趋势（分别提升11%、10%与2%）。两种咖啡源生物炭的施用效果，尤其是CH，均优于仅施用有机粪肥的对照组土壤。咖啡废弃物来源的生物炭是改善砂质土壤质量的极具潜力的工具。