Abstract:
The interactive effect of biochar, cattle manure and nitrogen (N) fertilizer on
the dynamics of carbon (C) mineralization and stabilization was investigated
in a sandy soil amended with three sole biochar (0, 20 or 40 t ha−1) or
manure (0, 13 or 26 t ha−1) and four combined biochar-manure levels (20 or
40 t ha−1 biochar plus 13 or 26 t ha−1 manure) with or without N fertilizer (0
or 90 kg ha−1) and CO2-C evolution measured over 54-d incubation period.
Biochar application, solely or combined with manure resulted in lower
applied C mineralized (ACM), indicating C sequestration in the soils.
Negative attributable effect (AE) of co-application of biochar and manure
on C mineralization was observed relative to the sole treatments. Both ACM
and AE were negatively correlated with C/N ratio and mineral N content of
the soil-mixtures (r ≥ – 0.573; p ≤ 0.01), indicating microbial N limitation.
The double first-order exponential model described CO2-C efflux very well
and indicated that ≥94% of C applied was apportioned to stable C pools
with slower mineralization rate constant and longer half-life. Cumulative
C mineralized and modeled C pools were positively correlated with each
other (r ≥ 0.853; p ≤ 0.001) and with readily oxidizable C of soil-amendment
mixtures (r ≥ 0.861; p ≤ 0.001). The results suggested that co-application of
biochar and manure can promote initial rapid mineralization to release
plant nutrients but sequester larger amounts of applied C in refractive
C pool, resulting in larger C sequestration in sandy soils.
