Coffee Wastewater for Acidifying Animal Bone-Meal: Impacts On Crop Growth and Phosphorus Nutrition in P Deficient Soils in Ethiopia.

Establishing a reliable phosphorus (P) supply is critical for assuring long-term, sustainable food security, especially considering the fact that more than one billion people (i.e., one-sixth of the world’s population) suffer from chronic hunger.  Most Ethiopian soils are deficient in P, and crops are expected to respond to P fertilizer.  Although di-ammonium phosphorus (DAP) fertilizer is available in Ethiopia, the cost is too high for most farmers.   Since Ethiopia is the country with the highest number of livestock in Africa, animal bones were evaluated as sources of P-fertilizer for plant growth. The standard material used for comparison was DAP, a source of water-soluble P that is generally considered to be fully plant available. The animal bone-based materials comprised finely-ground (< 2 mm) and coarsely-ground (> 2mm) bone meals (FBM and CBM, respectively), with or without coffee waste-water acidification. Evaluation was accomplished through greenhouse trials using maize (Zea mays) and haricot bean (Phaseolus vulgaris) as the test crops. A P deficient soil was amended with FBM and CBM – with or without coffee wastewater – and DAP at the same P rate, 20.24 mg kg^-1. A control without bone-meal and no DAP addition was included. Measured variables were plant dry-matter yield, plant P concentration, and offtake of P in the harvested plants. Results will be shown with discussion focusing on the usefulness of coffee wastewater for acidifying bone-meal, including the impacts of grinding on P availability.