Inorganic phosphorus is also increased anthropogenically through the addition of bone and ash to the soil. Bone is one of the largest contributors to anthropogenically-augmented phosphate levels because phosphorus is present in bone as hydroxyapatite, which is not affected by plant uptake of the nutrient (Weston 1995:20). The Experimental Earthworks Project 1960-1992 in England (Crowther 1996) illustrated how the decomposition of bones affects phosphate levels, based on soil type and the length of time bone is in the ground. Bones are very high in phosphates, and are approximately 60% hydroxyapatite (ibid.: 195). The study found that phosphorus is dispersed from bones into soil in 32 years even in basic soils (ibid.: 196), and are permanently retained.
The first application of a more systematic approach to phosphate analysis in archaeology was performed at the Sutton Hoo burial site in England (Barker et al. 1975), where phosphate analysis was used in an attempt to identify the area where a body may have been, as no body was identified during the excavations. No specific concentration of phosphates was identified, but the entire burial mound area exhibited general enhancement.
Burial patterning was verified when phosphate analysis was used to pinpoint the location of burials at cemetery sites in the United States of America, Scotland and England in the 1950s (Solecki 1951; Johnson 1956; Biek 1957), where phosphate silhouettes were identified directly corresponding to grave plots. Cemeteries are identifiable as a series of similar patterns located in a single area.
Burial patterning indicating a known altar stone in the Dun Kilmore enclosure was also used as a grave marker
Phosphate patterning indicates the presence of a burial located directly to the north of an identified altar in the Dun Kilmore early Christian ecclesiastical enclosure. An isolated, relatively high increase in phosphate content can be representative of a burial. Burial sites are visible in phosphate patterning as relatively small areas of relatively very high phosphate content (4.5-6) with areas of relatively very low phosphate content (0.5-2.5) surrounding the phosphate increase. The specific phosphate pattern indicating the presence of a burial site will directly correspond to the size and position of the buried human remains. This patterning needs to be corroborated contextually because isolated phosphate increases can be caused by any number of contributors. At this site, the interpretation of this pattern as a burial site is corroborated by the presence of the associated altar stone and cemetery within the early Christian ecclesiastical enclosure at Dun Kilmore.