Carbon fractionation in a mine soil amended with compost and biochar and vegetated with Brassica juncea L

Journal of Geochemical Exploration

Volume 169, October 2016, Pages 137–143

http://dx.doi.org/10.1016/j.gexplo.2016.07.021

The aim of this study was to evaluate the effect of the application of compost and biochar as soil amendments and planting of Brassica juncea L. to improve soil carbon fractions in a copper mine soil. A greenhouse experiment was carried out for 3 months amending the mine soil with increasing proportions of compost and biochar mixture (20, 40, 80 and 100%) and planting Brassica juncea L. The results showed that the addition of amendments increased soil pH from 2.7 to 8.66, TC from undetectable levels to 149 g kg− 1, SOC from undetectable levels to 128 g kg− 1 and TN from undetectable levels to 11.13 g kg− 1. Organic amending also increased DOC (dissolved organic carbon) from undetectable levels to 25.56 g kg− 1, FOM (carbon in the free organic matter) from undetectable levels to 38.04 g kg− 1, FAP (carbon in fulvic acids removed with phosphoric acid) from undetectable levels to 15.57 g kg− 1, as well as increased the humification ratio, the humification index, the polymerisation rate and the organic carbon in the humified fractions (humic acids, fulvic acids and humin). Soils amended and vegetated with Brassica juncea showed lower values for FOM and FAP and higher values for humification ratio and polymerisation rate than the amended not-vegetated soils. Therefore, the combination of compost and biochar as soil amendment can be considered an efficient treatment to improve soil carbon fractions, making it suitable for a field scale application.

Build-up of carbon fractions in technosol-biochar amended partially reclaimed mine soil grown with Brassica juncea

Journal of Soils and Sediments

May 2016, Volume 16, Issue 5, pp 1529–1537

DOI: 10.1007/s11368-016-1358-9

Soil organic carbon (SOC) and its labile fractions are strong determinants of physical, chemical and biological properties. The objective of the present work was to evaluate the effects of organic amendments (technosol made of wastes and biochar) and Brassica juncea L. on the soil C fractions in a reclaimed mine soil.

The studied soil was from a former copper mine that was subsequently partially reclaimed with vegetation and wastes. A greenhouse experiment was carried out to amend the mine soil with different proportions of technosol and biochar mixture and planting B. juncea. B. juncea plants can tolerate high levels of metals and can produce a large amount of biomass in relatively short periods of time.

The results showed that with the addition of biochar and wastes, soil pH increased from 2.7 to 6.18, SOC from undetectable to 105 g kg−1 and soil total nitrogen (TN) from undetectable to 11.4 g kg−1. Amending with wastes and biochar also increased dissolved organic carbon (DOC) from undetectable to 5.82 g kg−1, carbon in the free organic matter (FOM) from undetectable to 30.42 g kg−1, FAP (carbon in fulvic acids removed with phosphoric acid) from undetectable to 24.14 g kg−1 and also increased the humification ratio, the humification index, the polymerisation rate and the organic carbon in the humified fractions (humic acids, fulvic acids and humin). Soils amended and vegetated with B. juncea showed lower FOM values and higher humification index values than the soils amended only with biochar and wastes.

This study concludes that the combined addition of wastes and biochar has a greater potential for both increasing and improving organic carbon fractions in mine soils. The authors recommend the application of biochar and technosol made of wastes as a soil amendment combined with B. juncea on soils that are deficient in organic matter, since they increased all of the SOC fractions in the studied copper mine soil.