Effectiveness of meat and bone meal and distillers grain ash as a phosphorus source for crops
Production of biogas from organic materials via gasification also generates a valuable byproduct of ash. Ash contains the original nutrient present in organic materials, except carbon, nitrogen and sulfur that are lost as gases during this process. Therefore, the ash is concentrated in the important macronutrient of phosphorus and potassium. To determine the feasibility of land application of ash in providing phosphorus for crops, a study was carried out using Brown Chernozemic soil in growth chamber and field. This study aimed to investigate the influence of two ashes applied at three rates of P in comparison with mineral P fertilizer on crop yield, and P species that resided in soil after harvest using a sequential extraction procedure. The experimental treatments for the growth chamber study included 3 P sources: distillers grain ash, meat & bone meal ash and mono-calcium phosphate fertilizer. Each P source was applied at 3 rates: 25, 50 and 100 kg P ha-1 in addition to a control. Each treatment was supplemented with 200 kg urea-N ha-1 to ensure that N is not a limiting factor. For the field study, the experimental treatments consisted of the same P sources with 3 rates of application: 20, 40 and 80 kg P2O5 ha-1 plus a control. Each treatment was also supplemented with 100 kg urea-N ha-1. Analysis of ashes co-produced from gasification of distillers grain and meat & bone meal showed that they are rich in phosphorus, ranging from 13 – 16 % P. This high content of P was observed to benefit crop growth, providing a significant increase in crop yield compared to the control. Both ashes produced yields similar to that of mineral phosphorus, suggesting the high availability of ash P for plant uptake. A high proportion of residual P from the meat & bone meal ash was present in the form of calcium phosphate in the soil.
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