Abstract
Abstract. Agricultural intensification has contributed greatly to the sustained food supply of China's population of 1.3 billion over the 30-year period from 1982 to 2011. Intensification has several and widely recognized negative environmental impacts including depletion of water resources, pollution of water bodies, greenhouse gas emissions and soil acidification. However, there have been few studies over this period on the impacts of intensification on soil organic carbon (SOC) at the regional level. The present study was conducted in Huantai County, a typical intensive farming region in northern China, to analyze the temporal dynamics of SOC influenced by climate and farming practices. The results indicate that from 1982 to 2011, SOC content and density in the 0–20 cm layer of the cropland increased from 7.8 ± 1.6 to 11.0 ± 2.3 g kg−1 (41%) and from 21.4 ± 4.3 to 33.0 ± 7.0 Mg ha−1 (54%), respectively. The SOC stock (0–20 cm) of the farmland for the entire county increased from 0.75 to 1.2 Tg (59%). Correlation analysis revealed that incorporation of crop residues significantly increased SOC, while an increase in the mean annual temperature decreased the SOC level. Therefore, agricultural intensification has increased crop productivity and contributed to SOC sequestration in northern China. In the near future, more appropriate technologies and practices must be developed and implemented for a maintenance or enhancement of SOC in this region and elsewhere in northern China, which also reduce non-CO2 greenhouse gas emissions, since the climate benefit from the additional SOC storage is estimated to be smaller than the negative climate impacts of N2O from N fertilizer additions.
Highlights
Increasing soil organic matter (SOM) storage in arable lands can ensure the sustained supply of nitrogen (N) and other nutrients to crop growth and maintain appropriate soil quality such as aeration, permeability, water-holding capacity and nutrient preserving capacity (Smith et al, 2012)
The mean soil organic carbon (SOC) content of land used for vegetable cultivation increased to cropland, i.e., from 7.8 ± 1.6 to 11.0 ± 2.8 g kg−1
This trend indicates that the rate of increase in SOC content and density of cropland (0–20 cm) in Huantai County since the early 1980s has been 0.11 g kg−1 yr−1 and 0.40 Mg ha−1 yr−1, respectively
Summary
Increasing soil organic matter (SOM) storage in arable lands can ensure the sustained supply of nitrogen (N) and other nutrients to crop growth and maintain appropriate soil quality such as aeration, permeability, water-holding capacity and nutrient preserving capacity (Smith et al, 2012). Accumulation of SOM or soil organic carbon (SOC) stock in arable lands, which contribute to the mitigation of greenhouse effect and a concomitant improvement in soil fertility (Matson et al, 1997; Sainju et al, 2009), may be achieved by a range of improved farming practices. These practices include adoption of high-yielding crop varieties, balanced fertilization, crop residue incorporation, no-till (NT) or reduced tillage, optimal irrigation, high cropping intensity (Matson et al, 1997; Kucharik, et al, 2001). In the Netherlands, the SOC content of arable land increased by about 0.08 g kg−1 yr−1 between 1984 and 2004 (Reijneveld et al, 2009). Benbi and Brar (2009) reported that SOC in the Punjab state of India increased from 2.9 to 4.0 g kg−1 (38 %) between 1981 and 2006, largely resulting from irrigation, optimal fertilization, and an increase in crop productivity
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