Effects of Treating Animal Bones with Coffee Wastewater On Crop Growth and Phosphorus Nutrition in Clay and Loam Soils of Ethiopia.

Establishing a reliable phosphorus (P) supply is essential for assuring long-term sustainable food security. Not only are the world’s supplies of minable P running out, but the quality of the existing phosphate rock, which is the source of P fertilizers in modern agriculture, is also rapidly decreasing, as a result of which the cost of production is increasing. With more than one billion people - one sixth of the world’s population - suffering from chronic hunger, acquiring enough P to grow food will be a significant challenge for humanity in the future. The aim of this study was to evaluate the effectiveness of coffee wastewater for acidifying animal bones (a waste material from abattoirs or home-based slaughtering) to increase P release/availability for growing plants. We conducted an experiment where maize (Zea mays L.) and haricot bean (Phaseolus vulgaris) were grown in a greenhouse pot trial utilizing clay and loam soils (0-15 cm depth) collected from farmers’ field in southern Ethiopia. Soils were amended with different bone-based fertilizers (coarsely-ground and finely-ground with and without coffee wastewater acidification) and compared with soils fertilized with di-ammonium phosphate (DAP). Bone-based fertilizers and DAP were applied at the same P rate, 46 kg P₂O₅ ha^-1. A control without bone and DAP was included in the experiment. Measured parameters include dry matter (DM) yield and P uptake. Results from this experiment will be covered in a poster presentation, with discussion focusing on the usefulness/effectiveness of coffee wastewater for acidifying animal bones and thus P release, as well as the impact of grinding on P availability.