Effects of long-term tillage on carbon partitioning of nematode metabolism in a Black soil of Northeast China

Conservation tillage is one of the major strategies for maintaining agricultural sustainability and has significant beneficial effects on soil organic carbon (C) retention and soil organism diversity. However, how changes in soil organism populations and/or community structure under different tillage practices contribute to C sequestration in soil is not well documented. In this paper, soil nematode assemblages were used as a model to quantify C allocation in production and respiration of soil organisms in a long-term tillage trial initiated in 2001 on a Black soil (Typic Hapludoll) of Northeastern China. Soils were sampled from no tillage (NT), ridge tillage (RT) and conventional tillage (CT) practices in the soybean (Glycine max Merr.) phase of the maize (Zea mays L.) -soybean rotation. In comparison with CT, RT and NT significantly increased production and respiration C of nematodes as a consequence of more basal C flowing into soil food web. The significantly increased bacterivore metabolic C in both production and respiration under RT and NT suggests that a bacterial-channel was the predominant pathway for C entering the food web. However, the efficiency of C allocation into soil nematodes, as indicated by the ratio of respiration C to production C (R/P), varied widely between RT and NT. NT significantly improved the C storage capacity of almost all nematode trophic groups while RT predominantly promoted the C storage capacity of bacterivores. Our results suggest that NT is more favorable than RT for allocating C into soil organisms under long-term application in the Black soil of Northeast China.