Phosphorus content in bovine bone, and potential of this organic residue to increase the nutritional profile of agricultural soils.

The objective of this work was to determine the total phosphorus and water-extractable phosphorus content of an incinerated bovine tibia bone sample without marrow. Three acid digestions were compared; nitric acid and perchloric acid, hydrochloric acid and hydrogen peroxide, and hydrochloric acid. The digestions were preceded by incineration of the sample at 800 °C for 8 h. Concerning water-extractable phosphorus, two bone : water ratios were contrasted, that is 1 : 100 and 1 : 200. The total phosphorus mass in the evaluated bone sample was 44,177 ± 0,810 %P2O5 (w/w DW), and, pragmatically, the three acid digestion alternatives yield comparable values. The water-extractable phosphorus content per dry mass of the incinerated bone material was 0,013 ± 0,001 and 0,040 ± 0,001 %P2O5 (w/w DW) for the 1 : 100 and 1 : 200 treatments, respectively; the higher extraction of phosphorus in the 1 : 200 ratio, despite being the most diluted option, could be related to a lower impact of this treatment on the pH of the mixture, which could have favored a greater displacement of phosphorus from the incinerated bone to the water. If the reference is the water-extractable phosphorus content in the 1 : 200 ratio, there are only 0.090 g of water-extractable phosphorus per 100 g of total phosphorus in the incinerated bone sample studied; this water-extractable phosphorus fraction could be increased by using phosphate-solubilizing bacteria.