months after compost application, but declined at 16
months corresponding to similar declines in SOC (Fig. 4).
The significant increases preceding 11 months occurred
for all compost application rates and for unamended soil.
Dissolved organic C significantly increased again from 16
to 23 months for all treatments, but did not decline at 29
months. In contrast to the relative stability of SOC for unamended soil after compost application, DOC was signifi-
cantly greater at successive sampling times from 0 to 29
months, with the exception of the 16 month sampling time
during winter dormancy. Since no compost was added to
unamended soil, the increases in DOC were attributed to
C contribution by St. Augustinegrass. Application rate
had less effect on DOC than SOC. On average, composts
resulted in 11% higher DOC at 160 Mg ha1 than at
80 Mg ha1
, and 13% higher DOC than in unamended soil.
The highest DOC for all sampling times occurred with St.
Augustinegrass receiving 160 Mg ha1
, while the unamended
soil had the lowest DOC. The 80 Mg ha1 rate
produced significantly lower DOC than 160 Mg ha1
, yet
exhibited higher DOC than unamended soil.
Dis