Data_Sheet_1_Biochar as Influenced by Feedstock Variability: Implications and Opportunities for Phosphorus Management.docx

Agricultural wastes from plant and animal operations are often land applied to recycle and manage residues. Compositional variability among these wastes is vast. Some waste components can potentially represent a threat to the environment and humans depending on their nature, application loads, and soil type. Biochar, the product obtained by biomass heating under oxygen-limited conditions, has the potential to minimize risks associated with waste characteristics while promoting soil health. However, variation in the residue wastes (feedstocks) used to produce biochar carries over to the resultant biochar. In this study, we compare the chemistry and composition of biochars representing two broadly defined sources—animal (poultry litter, biosolids) and plant (mixed hardwoods, pure maple, pine)—and highlight phosphorus (P) management implications and opportunities presented by the variability among them. We also evaluate P leaching patterns of four selected biochars (poultry litter, biosolids, hardwoods, and maple) as applied at an identical rate (1% w/w) to two soils differing in P retention capacities. Cumulative P release following poultry litter biochar application and 20 leaching events was much lower for the more P retentive soil. Total P release from biochar-amended soils did not differ between soils when biochar from biosolids or from plant sources were used as the soil amendment. However, the biosolids-biochar released higher levels of P initially from the Candler compared with the Apopka (more P retentive than the Candler) soils, similar to that of poultry litter biochar. Compositional variations in feedstocks and resultant biochars must be understood in order to judiciously use them as crop nutrient amendments. There is potential to minimize nutrient deficiencies and environmental liabilities of biochars by matching feedstocks, or mixtures of feedstocks, to the needs of specific crops, and by considering the P retentive capacity of the soil where the biochar is applied.

来自动植物生产过程的农业废弃物常被施用于农田，以实现资源循环与废弃物处置。此类废弃物的组成变异度极高，部分组分依其性质、施用量及土壤类型的不同，可能对环境与人体健康构成潜在威胁。生物炭（biochar）是指在限氧条件下对生物质进行热解所得的产物，其既可降低因废弃物特性带来的风险，又可促进土壤健康。然而，用于制备生物炭的残留废弃物原料（feedstocks）的组成变异，会传递至最终制得的生物炭中。

本研究针对两大类宽泛定义的来源所制得的生物炭——动物源（家禽垫料、生物固体）与植物源（混合硬木、纯枫木、松木）——比较其化学性质与组成，并阐明其组成变异对磷（P）管理的影响与应用潜力。本研究还以1%的质量分数（1% w/w）将四种筛选出的生物炭（家禽垫料源、生物固体源、硬木源与枫木源）分别施用于两种磷持留能力存在差异的土壤，以此评估其磷淋失模式。

在经过20次淋洗事件后，施用家禽垫料源生物炭的高磷持留能力土壤的累计磷释放量显著更低。当以生物固体源或植物源生物炭作为土壤改良剂时，施加生物炭的两类土壤的总磷释放量并无显著差异。不过，与阿波普卡（Apopka，磷持留能力强于坎德勒（Candler））土壤相比，生物固体源生物炭在坎德勒土壤中初始释放的磷水平更高，这一表现与家禽垫料源生物炭相似。

要合理将生物炭用作作物营养改良剂，必须明晰原料与最终制得的生物炭的组成变异。通过匹配原料（或原料混合物）以适配特定作物的需求，并结合施用生物炭的土壤的磷持留能力，可有效降低生物炭引发的养分匮乏问题与环境负担。