Phosphorus forms in soil amended with meat and bone meal ash and dried distillers grain ash

Abstract

Biogas production from organic materials via gasification process 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. If this ash is land-applied, ash phosphorus may reside in soil in different forms. Therefore, 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. Specifically, this study aimed to investigate the influence of two ashes applied at three rates of P in comparison with mineral P fertilizer on P species that resided in soil after harvest using a sequential extraction procedure. Plant phosphorus recovery was also investigated. The experimental treatments for the growth chamber study included 3 P sources: dried distillers grain ash (DDGA), meat & bone meal ash (MBMA) and mono-calcium phosphate fertilizer (MP). 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. Analysis of ashes co-produced from gasification of distillers grain and meat & bone meal showed that they are rich in phosphorus, ranging from 18 – 19 % P. A high proportion of residual P from the meat & bone meal ash was present in the form of calcium phosphate in the soil. The most labile forms of P was higher in DDGA treatments compared to MBMA. Phosphorus recovery in DDGA treatments was similar to that of MP treatments, and greater than MBMA.