Abstract:
Home gardens are an integral component of dry zone agroecosystems of Sri Lanka.
These sequester atmospheric CO2 and thereby contribute to mitigate global warming,
but agricultural practices performed in these are believed to be disturbing the soil,
resulting the release of stored soil carbon to the atmosphere. Further, soil organic
matter affects the retention of soil nutrients. Thus, the amount of soil carbon, and the
available nitrogen and phosphorous contents in the soils of home gardens could vary
with the management inputs. Therefore, the C sequestration capacity in the soils (0–
15 and 15–30 cm depths) from three types of dry zone home gardens (intensely
managed over a long period of time, poorly managed over a long time and intensely
managed but recently established) in Anuradhapura District in the North Central
province of Sri Lanka were studied in relation to major management interventions
operated in these. The total organic carbon (TOC), Labile soil organic carbon (LC),
Microbial Biomass carbon (MBC) Water soluble carbon (WSC), available phosphorus,
NH4
+ nitrogen and NO3
- nitrogen contents in 108 randomly selected pooled soil
samples (a composite of three) were detected by performing standard protocols, and
the soil carbon stocks (SCS) in these three home gardens were estimated. TOC, LC,
WSC and MBC contents in upper soil layers of more intensely and less intensely
managed home gardens did not vary significantly (p >0.05). Also, the SCSs do not vary
significantly with the intensity of agricultural practices in these home gardens.
However, the examined home gardens appear to be sequestering carbon at a
substantial level, ranging from 21.17–23.81 Mg ha-1
in the top-soil, but compared with
this, the carbon stock is lower at the 15-30 cm soil depth (14.27–18.82 Mg ha-1
). The
available phosphorous content at 0–15 cm soil depth, and the available phosphorous,
NH4
+ nitrogen and NO3
- nitrogen contents at 15–30 cm soil depth in intensely managed
home gardens were higher (p <0.05) than that in less intensively managed home
garden, and this can be attributed to the addition of chemical and organic fertilizers
to the top-soil and subsequent leaching of nutrients to the subsoil.
