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Abstract:
Soil amendment with hydrochar produced by
hydrothermal carbonization of biomass is suggested as a simple, cheap, and effective method for increasing soil C. We
traced C derived from corn silage hydrochar (δ13C of −13‰)
added to “coarse” and “fine” textured soils (δ13C of −27‰for
native soil C (SOC)) over two cropping seasons. Respiration
rates increased in both soils (p<0.001) following hydrochar
addition, and most of this extra respiration was derived from
hydrochar C. Dissolved losses accounted for ~5 % of added
hydrochar C (p<0.001). After 1 year, 33±8 % of the added
hydrochar C was lost from both soils. Decomposition rates for
the roughly two thirds of hydrochar that remained were very
low, with half-life for less estimated at 19 years. In addition,
hydrochar-amended soils preserved 15±4 % more native SOC
compared to controls (negative priming). Hydrochar negatively
affected plant height (p<0.01) and biomass (p<0.05) in the
first but not the second crop grown on both soils. Our results
confirm previous laboratory studies showing that initially,
hydrochar decomposes rapidly and limits plant growth.
However, the negative priming effect and persistence of added
hydrochar C after 1 year highlight its soil C sequestration potential, at least on decadal timescales.
