~10 µg DNA/g soil
||Landenmark HK, Forgan DH, Cockell CS. An Estimate of the Total DNA in the Biosphere. PLoS Biol. 2015 Jun 11 13(6):e1002168. doi: 10.1371/journal.pbio.1002168. p.3/10 bottom paragraphPubMed ID26066900
|| Zhou J, Bruns MA, Tiedje JM. DNA recovery from soils of diverse composition. Appl Environ Microbiol 1996 62(2) 316–322.  Plassart P, Terrat S, Thomson B, Griffiths R, Dequiedt S, Lelievre M, et al. Evaluation of the ISO Standard 11063 DNA extraction procedure for assessing soil microbial abundance and community structure. PLoS ONE 2012 7(9): e44279. doi: 10.1371/journal.pone.0044279PubMed ID8593035, 22984486
||p.3/10 bottom paragraph:"[Investigators] utilised data on DNA concentrations in soil and water to achieve a much coarser-grained global estimate of the quantity of DNA in the environment. The quantity of dissolved DNA in aquatic environments is of the order of 10 µg/l [BNID 111598] and the total volume of aquatic habitats on Earth is 1.4 × 10^21 l [refs 5,27], giving a total quantity of DNA of approximately 1.4 × 10^31 Mb. Similarly, the concentration of DNA in soil is about 10 µg DNA/g soil [primary sources]."