Eg. Gregorich et al., FERTILIZATION EFFECTS ON SOIL ORGANIC-MATTER TURNOVER AND CORN RESIDUE C STORAGE, Soil Science Society of America journal, 60(2), 1996, pp. 472-476
Soil organic matter turnover is influenced by N; thus long-term fertil
ization of corn (Zea mays L,) may significantly affect soil organic ma
tter levels. Effects of fertilization on soil organic matter turnover
and storage of residue C under continuous corn were evaluated using so
ils from a long-term field experiment in Ontario, Total organic C and
natural C-13 abundance measurements indicated that fertilized soils ha
d more organic C than unfertilized soils, the difference accounted for
by more C-4-derived C in the fertilized soils. About 22 to 30% of the
soil C in the plow layer had turned over and was derived from corn in
the fertilized soils; in unfertilized soils only 15 to 20% was derive
d from corn. Assuming that organic matter turnover follows first-order
kinetics, the half-life of C-4-derived C in the surface 10 cm of both
soils was the same, about 19 yr. Natural C-13 abundance measurements
and estimates from a soil organic matter model indicate that 10 to 20%
of the added residue C was retained in the soil. Fertilized soils had
more light fraction (LF) C than unfertilized soils. More than 70% of
the C in the LF of fertilized soils was derived from corn; in unfertil
ized soils only 41% was derived from corn. The half-life of C-3-derive
d C in the LF was shorter than 10 yr, These results indicate that adeq
uate fertilization increases crop yields, in turn leading to greater C
storage, and that fertilization does not significantly alter the rate
of turnover of native soil organic matter.