Forms and Levels of Phosphorus in a Strongly Weathered Acid Soil in Ghana: The Contribution of Corn Cob Biochar

Different rates of corn cob biochar were applied to a strongly weathered acid soil as an amendment. The impact of the amendment on levels and forms of phosphorus (P) was determined. The biochar was applied to the soil at a rate of 0, 26, 52, 78 and 150 t ha-1. The amended soil was incubated in a greenhouse for a period of 1 – 8 weeks. Sub samples of the unamended/control and amended soils were taken at periods of 2, 4, 6 and 8 weeks and then analysed for pH, total P, Bray – 1 P and water – extractable P. Significant improvements were recorded in the pH of the amended soil. The application rate of 150 t ha-1 recorded the highest increase in pH (78.4%) while the lowest change (64.9%) was recorded by the application rate 52 t ha-1. The total P decreased as the rate of amendment increased, implying that total P was mineralized as the amount of carbon in the amendment increased. This resulted in the increase in available P. The yield of lettuce (Lactuca sativa) generally increased with rate of biochar application but the P content in the shoot of the plant was less than the optimum.