Abstract
Soil type and fertility level influence straw carbon dynamics in the agroecosystems. However, there is a limited understanding of the dynamic processes of straw-derived and soil-derived carbon and the influence of the addition of straw carbon on soil-derived organic carbon in different soils associated with different fertility levels. In this study, we applied the in-situ carborundum tube method and 13C-labeled maize straw (with and without maize straw) at two cropland (Phaeozem and Luvisol soils) experimental sites in northeast China to quantify the dynamics of maize-derived and soil-derived carbon in soils associated with high and low fertility, and to examine how the addition of maize carbon influences soil-derived organic carbon and the interactions of soil type and fertility level with maize-derived and soil-derived carbon. We found that, on average, the contributions of maize-derived carbon to total organic carbon in maize-soil systems during the experimental period were differentiated among low fertility Luvisol (from 62.82% to 42.90), high fertility Luvisol (from 53.15% to 30.00%), low fertility Phaeozem (from 58.69% to 36.29%) and high fertility Phaeozem (from 41.06% to 16.60%). Furthermore, the addition of maize carbon significantly decreased the remaining soil-derived organic carbon in low and high fertility Luvisols and low fertility Phaeozem before two months. However, the increasing differences in soil-derived organic carbon between both soils with and without maize straw after two months suggested that maize-derived carbon was incorporated into soil-derived organic carbon, thereby potentially offsetting the loss of soil-derived organic carbon. These results suggested that Phaeozem and high fertility level soils would fix more maize carbon over time and thus were more beneficial for protecting soil-derived organic carbon from maize carbon decomposition.
Highlights
Soil organic carbon (SOC) is important to cropland soil, and it influences carbon balance and soil fertility in agroecosystems [1,2]
Total organic carbon content in the treatment with maize straw during the experimental period was in the order of high fertility Phaeozem > high fertility Luvisol > low fertility Phaeozem > low fertility Luvisol, while δ13C was in the order of low fertility Luvisol > low fertility Phaeozem > high fertility Luvisol > high fertility Phaeozem
The order of total organic carbon content showed that high fertility Phaeozem > high fertility Luvisol > low fertility Phaeozem > low fertility Luvisol, while the δ13C followed the order of low fertility Luvisol > high fertility Luvisol > high fertility Phaeozem > low fertility Phaeozem
Summary
Soil organic carbon (SOC) is important to cropland soil, and it influences carbon balance and soil fertility in agroecosystems [1,2]. The application of organic material (e.g., crop residues) is one of the major sustainable management practices of cropland soils, and it increases or reduces the amounts of carbon inputs or outputs; improves soil physical, chemical and biological properties; potentially accomplishes the restoration of SOC and improves soil fertility [4,5,6,7]. It is important for carbon transformation for conventional agriculture cropping systems in northeast China by transferring organic matter and nutrients to the soil [8,9,10,11]. Few studies have compared organic material decomposition between different soil types or different soil fertility levels [15,16,17]; even fewer studies have quantified the process of external carbon transformation and its contribution to SOC in different cropland soils associated with different fertility levels to examine the interactions of soil type and soil fertility level with external carbon transformation
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