Carbon and nutrient dynamics in biochar co-composts and their effects on C balances, soil properties and crop yields in Ghana

撒哈拉以南非洲地区的土壤有机碳和养分含量天然较低，而且往往因不可持续的土地管理做法而进一步退化，导致作物产量低。维持或更好地增加土壤有机碳对于提高土壤肥力，实现农业可持续生产具有至关重要的作用。然而，在非洲，提高有机碳水平的材料的可用性是有限的，而且它们的使用往往伴随着快速的矿化和高浸出损失。有机家庭和市场废弃物堆肥在一些地区是一项新兴技术，但在生产过程中和田间施用后的高碳氮损失降低了其效率。根据其他研究和一些自己的初步结果，添加生物炭似乎是一个有希望的选择，可以提高堆肥的稳定性，从而提高土壤肥力。然而，在共堆肥和土壤掺入过程中碳和养分保持的潜在机制仍然知之甚少。因此，该项目的总体目标是：1)调查生物炭共混堆肥对堆肥过程中碳氮动态的影响；2)研究和记录堆肥生物炭施用对加纳农业生产典型土壤中土壤质量指标、温室气体排放和作物产量影响的潜在机制。该项目将与来自海岸角大学（加纳）的Kwame Frimpong博士进行合作研究，在加纳进行堆肥生产、温室试验和实地试验，在波宏进行实验室试验和综合物理、化学和生物堆肥和土壤表征。堆肥将由有机生活垃圾、稻草和家禽粪便混合而成，再用两种不同的生物炭（稻壳和玉米芯）的不同比例进行修正。在堆肥生产过程中以及在加纳的三个现场应用之后，将监测温室气体（CO2、N2O、NH3和CH4）的排放。生物炭和生物炭-堆肥特性的相关变化将在堆肥和田间暴露在网袋中的样品中进行分析。来源分化的碳平衡将从13C数据中计算，碳稳定机制将从顺序提取和密度和聚集分数中确定。结合温室和田间试验的产量数据，本研究结果将显示生物炭共堆肥的生产和应用是否可以提高这些热带土壤的碳固存、土壤肥力和作物产量。

Soils in Sub-Saharan Africa are naturally low in SOC and nutrients and are often further degraded by unsustainable land management practices, resulting in low crop yields. Maintaining or better, increasing soil organic carbon plays a crucial role in enhancing soil fertility for sustainable agricultural production. However, the availability of materials for increasing SOC levels is limited in Africa, and their use is often accompanied by rapid mineralization and high leaching losses. Composting organic household and market wastes is an emerging technology in some areas but high carbon and nitrogen losses during production and after field application reduce its efficiency. Based on other studies and some own preliminary results, the addition of biochar appears to be a promising option for increasing compost stability and thus its suitability for improving soil fertility. However, the underlying mechanisms for C and nutrient retention during co-composting and soil incorporation are still poorly understood. Therefore, the general objectives of the project are i) to investigate the effects of biochar co-composting on C and N dynamics during composting and ii) to study and document the mechanisms underlying the effect of composted biochar application on soil quality indicators, greenhouse gas emissions and crop yield in typical soils used for agricultural production in Ghana.The project will be conducted as a collaborative study with Dr. Kwame Frimpong from the University of Cape Coast (Ghana) involving compost production, greenhouse experiments and field trials in Ghana and laboratory experiments and comprehensive physical, chemical and biological compost and soil characterization in Bochum. Compost will be produced from a mixture of organic household wastes, rice straw and poultry manure, amended with different rates of two different biochars (from rice husks and corn cobs). During compost production and after its application to the three field sites in Ghana, the emissions of greenhouse gases (CO2, N2O, NH3 and CH4) will be monitored. The associated changes in biochar and biochar-compost properties will be analyzed in samples exposed in mesh bags in the compost and in the field. Source-differentiated C balances will be calculated from 13C data and C-stabilizing mechanisms will be determined from sequential extractions and from density and aggregate fractions. Together with the yield data from the greenhouse and field experiments, the results of this study will show if the production and application of biochar co-composts can enhance C sequestration, soil fertility and crop yield in these tropical soils.