Effects of experiment duration on carbon mineralization and accumulation under no-till

Abstract

Conservation tillage incorporating no-till (NT) is often recommended to reduce soil organic carbon (SOC) mineralization and sequester SOC, thus mitigating carbon dioxide production. The rates of SOC accumulation and mineralization are significantly affected by the time since the introduction of NT, however, there is currently poor understanding of exactly how rates change over time under long-term NT. Thus, an 11-year field experiment, a 60-day laboratory incubation, and a meta-analysis were used to better understand the effects of NT, experiment duration, and their interaction on SOC accumulation and mineralization. Our field experiment showed that, compared with plow tillage (PT), NT had a higher proportion of more stable SOC fractions and significantly increased SOC concentration by 12.6 % in the 5th year of the field experiment, and 52.2 % in the 11th year. A significant interaction between tillage and experiment duration was observed for SOC mineralization using laboratory incubation. NT decreased bulk SOC mineralization by 20.1 % in the 5th year of the field experiment and by 44.8 % in the 11th year when compared with PT. This was associated with an increase in SOC concentration and a decrease in SOC mineralization from macro-aggregates (>2 mm) over time and thus the accumulation of SOC was attributed to the physical protection of SOC within macro-aggregates. Meta-analysis confirmed these results and found that, compared with PT, NT significantly decreased SOC mineralization by ∼11 % when experiment duration was ≤8 years and by ∼27 % when it was 8–16 years (P < 0.05). This indicated that SOC mineralization was reduced in NT to an increasing degree as experiment duration increased and additional SOC could be sequestered with an experiment duration of up to 16 years.