Abstract
Crop straw is widely used to manage soil organic carbon (SOC) sequestration as an environmentally friendly practice in the North China Plain. However, little is known about the effects of straw returning modes on SOC sequestration in this region. Thus, a field experiment was conducted to study SOC accumulation and mineralization as well as aggregate stability and aggregate-associated SOC for the following three straw returning modes: no straw returning (NSR), only wheat straw returning (WR), and both wheat and maize straw returning (WR-MR). SOC concentration and storage were higher for WR and WR-MR than for NSR in the 0–20 cm soil layer, respectively (p < 0.05). Although WR and WR-MR resulted in higher mineralization per unit of soil than NSR, no significant difference in mineralization per unit of soil carbon was observed among straw returning modes in the upper soil layer. The mean weight diameters of aggregates at 0–5 cm were higher under treatments with crop retention than under NSR. At this soil depth, the aggregate-associated C concentration and stock for each soil size were significantly decreased by NSR. These findings suggest that WR-MR and WR are effective residue management practices. In particular, WR is the optimal strategy to enhance SOC sequestration, considering other applications of straw (e.g., forage, fuel, or biomass).
Highlights
Soil organic carbon (SOC) plays an important role in carbon sequestration and the mitigation of climate change; the amount of carbon (C) stored in soil (1580 Gt C) is two to three times higher than that in the global atmosphere [1,2,3]
Significant differences in the SOC concentration were observed under different straw returning modes in the upper 20 cm soil layer compared with the 20–50 cm layer (Table 2)
This study investigated SOC accumulation and mineralization as well as aggregate stability and associated SOC under different straw returning modes
Summary
Soil organic carbon (SOC) plays an important role in carbon sequestration and the mitigation of climate change; the amount of carbon (C) stored in soil (1580 Gt C) is two to three times higher than that in the global atmosphere [1,2,3]. SOC accumulation and sequestration in agro-ecosystems rely on the C input from crop straw (shoot, root, and root exudates) and C output from SOC mineralization by soil microbes [4]. Crop straw provides a source of fresh organic matter, and increases crop yield [6]. Any increase (decline) in agronomic yield per unit area leads to high (low) input of biomass C, further increasing (decreasing) soil quality and crop productivity [7]. Long-term field experiments showed that straw returning improves the SOC stock by 0.07–1.46 Mg ha−1 year−1 of carbon in northern China [8,9]. Zhao et al [10] evaluated SOC improvement from 1980 to 2011 in China and found that only 16.3% of the C input derived from crop straw was converted to SOC
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