Changes in topsoil organic carbon of croplands in mainland China over the last two decades

Abstract

By searching literature databases, we obtained more than 200 articles published since 1993 that related to the measurements of topsoil organic carbon (SOC) in different regions. To objectively evaluate the changes in the SOC over the last two decades, we selected 132 representative articles from these documented articles. More than sixty thousand soil samples and/or sampling sites were included in the selected articles. Results from analyzing these data sets indicated that the concentration of SOC increased in 53%-59%, decreased in 30%-31% and stabilized in 4%-6% of the national croplands, respectively. A further investigation showed that the total increment of SOC in Chinese croplands ranged from 311.3 Tg to 401.4 Tg. In terms of administrative region, significant increase occurred in eastern and northern China and decrease in northeastern China, respectively. When evaluated by soil great groups, the SOC increased considerably in paddy soils and fluvo-aquic soils and reduced conspicuously in black soils. The increase of SOC is attributed to the amendments of crop residues and organic manure, the augment of synthetic fertilizer application and the optimal combination of nutrients, and the development of no-tillage and reduced-tillage practice. Water loss and soil erosion and low input induced a great decrease of the SOC in black soils. In order to effectively enhance soil C sequestrations and to greatly control the SOC reduction in northeastern China, future efforts should be made in developing new techniques, training farmers and consummating the policy of governmental compensation, by which the application of crop straw, the improvement of fertilization, the practice of no-tillage and reduced-tillage, and the control of water loss and soil erosion could be further realized. To respond to the increasing pressure from the Kyoto Protocol thenceforward, four aspects were further addressed for future research needs, including the quantification of SOC storage in the Second State Soil Survey and at present, the understanding of control mechanisms in both anthropogenic and non-anthropogenic causes that determine SOC dynamics, the investigation of options that can effectively enhance SOC sequestration and/or reduce SOC loss, and the assessments of potentials and the likely SOC dynamics in the future on a national scale.

Effects of enhancing soil organic carbon sequestration in the topsoil by fertilization on crop productivity and stability: Evidence from long-term experiments with wheat-maize cropping systems in China

“…Low SOC stocks could reduce crop yield through effects on soil fertility and significant nutrient loss may also occur as a result of low nutrient buffer or retention capacity. Changes in SOC stocks have been reported extensively on the global (FAO, 2001), regional (Huang and Sun, 2006;Smith, 2004) and plot scales , which suggests that society has paid increasing attention to the potential for sequestering organic carbon in soils in an effort to mitigate climate change and promote crop productivity. For example, it has been reported that a 1% increase in SOC content of the topsoil (0-20 cm) could increase cereal yield by 430 kg ha −1 and reduce yield variability by 3.5% (Pan et al, 2009).…”

“…Furthermore, SOC losses from China's croplands have been widely reported (Huang and Sun, 2006;Qin et al, 2013;Sun et al, 2010). SOC stocks of agro-ecosystems may be increased by improving agronomic practices.…”

Increasing Soil Organic Matter Enhances Inherent Soil Productivity while Offsetting Fertilization Effect under a Rice Cropping System

“…On the other hand, SOM accumulation is an important option, not only to mitigate climate change, but also to improve soil quality because of its extensive impacts on soil physical, chemical, and biological properties [3,4]. In previous studies, changes of SOM in croplands have been quantified using different scales in China [5,6], however, the potential influence of the SOM change on crop yields and input requirements in the farmland systems is unclear because great uncertainty about the relationship between SOM and crop yield still remains.…”

Net global warming potential and greenhouse gas intensity in a double-cropping cereal rotation as affected by nitrogen and straw management

“…Many long-term field experiments have indicated that proper fertilization together with straw return can increase soil organic carbon (SOC) content (Huang and Sun, 2006;Mosier et al, 2006;Zhang et al, 2010;Shang et al, 2011). However, these practices may also stimulate N 2 O emissions by increasing the supply of substrates for soil nitrifiers and denitrifiers, and the resulting increase in microbial activity may offset the SOC sequestration effects (Pathak et al, 2005).…”