Influences of 13 Years New Conservation Management on Labile Soil Organic Carbon and Carbon Sequestration in Aggregates in Northeast China.

New conservation management (NCM) for summer maize monocultures might cause changes in the organic carbon composition when compared with conventional tillage (CT). To investigate the difference, the soil organic carbon (SOC) under 13 years of NCM and CT was studied in Northeast China. The NCM involved the use of a 40 cm and 160 cm narrow-wide row (maize was planted in the narrow row in two lines) with straw retained, but with no tillage and change in ridge direction. SOC in different soil aggregate size classes and labile organic carbon fractions at 0–10 cm, 10–20 cm and 20–40 cm depths were evaluated. The results showed that there was no significant difference in SOC content at a 0–10 cm depth, with values ranging from 19.9 to 21.1 g·kg−1 between two management systems. The contents of microbial biomass carbon (MBC) and light fraction organic carbon (LFOC) were significantly higher in NCM than in CT in the upper 10 cm. Among the labile organic carbon fractions, the light fraction organic C (LFOC) was the most sensitive to management change. The portion of macroaggregates (>0.25 mm) was higher under NCM than under CT and decreased with the increase in soil depth. NCM improved the organic carbon storage in aggregates 1–0.5 mm and reduced the organic carbon storage in microaggregates. It was concluded that NCM would be an effective and useful management choice for the enhancement of soil C sequestration in maize field systems in Northeast China. [ABSTRACT FROM AUTHOR]