Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/1997
Publication Date: N/A
Interpretive Summary: Conservation of soil organic carbon is important for improving soil physical, chemical, and biological properties. Improvement in soil quality can lead to increased plant production, reduced energy inputs, and less runoff of chemicals from agricultural fields. Increasing the slow pool of particulate organic carbon with conservation tillage may be a critical step in improving soil quality. Standing stock of particulate organic carbon was greater under zero tillage than under conventional tillage at the soil surface. Particulate organic carbon was also of higher quality (i.e., mineralizable) relative to other pools of soil organic carbon under zero tillage. Soil texture may play an important role in sequestering particulate organic carbon by limiting interactions with the more highly-reactive clay surfaces that enhance particulate organic carbon decompostion. Particulate organic carbon content was a more sensitive indicator of tillage-induced changes in soil organic carbon than the total amount of organic carbon. Zero tillage in this cold semiarid climate may increase both the active and slow pools of soil organic carbon within several years.
Technical Abstract: Conservation of soil organic carbon (SOC) is important for improving soil quality. Increasing the slow pool of particulate organic carbon (POC) with conservation tillage may be a critical step in improving the quality of agricultural soils. We determined the standing stock and potential mineralization rate of POC (material >0.053 mm diam) at depths of 0-50, 50-125, and 125-200 mm in four Boralfs (loam, silt loam, clay loam, and clay) under conventional shallow tillage (CT) and zero tillage (ZT) in northern Alberta and British Columbia. Standing stock of POC was different between tillage regimes only at a depth of 0-50 mm, averaging 6.3 Mg/ha under CT and 7.6 Mg/ha under ZT. The ratio of specific POC mineralization-to-specific whole-SOC mineralization averaged 23% greater under ZT than under CT, suggesting that POC was also of higher quality (i.e., mineralizable) under ZT relative to other pools of SOC. With increasing clay content, the portion of SOC as POC decreased, but the potential mineralization rate of POC increased. This result suggests that soil texture may play an important role in sequestering this slow pool of SOC by limiting interactions with the more highly-reactive clay surfaces that enhance POC turnover.