Soil organic carbon dynamics under long-term fertilizations in arable land of northern China

Abstract

Abstract. Soil carbon sequestration is a complex process influenced by agricultural practices, climate and soil conditions. This paper reports a study of long-term fertilization impacts on soil organic carbon (SOC) dynamic from six long-term experiments. The experiment sites are located from warm-temperate zone with a double-cropping system of corn (Zea mays L.) -wheat (Triticum Aestivium L.) rotation, to mild-temperate zones with mono-cropping systems of continuous corn, or a three-year rotation of corn-wheatwheat. Mineral fertilizer applications result in an increasing trend in SOC except in the arid and semi-arid areas with the mono-cropping systems. Additional manure application is important to maintain SOC level in the arid and semi-arid areas. Carbon conversion rate is significant lower in the warmtemperate zone with double cropping system (6.8%-7.7%) than that in the mild-temperate areas with mono-cropping systems (15.8%-31.0%). The conversion rate is significantly correlated with annual precipitation and active accumulative temperature, i.e., higher conversion rate under lower precipitation and/or temperature conditions. Moreover, soil high in clay content has higher conversion rate than soils low in clay content. Soil carbon sequestration rate ranges from 0.07 to 1.461 t ha −1 year −1 in the upland of northern China. There is significantly linear correlation between soil carbon sequestration and carbon input at most sites, indicating that these soils are not carbon-saturated thus have potential to migrate more CO 2 from atmosphere.

Characteristics of soil C:N ratio and δ13C in wheat-maize cropping system of the North China Plain and influences of the Yellow River

“…Based on our study and other studies that were conducted in the wheat-maize cropland of the North China Plain, SOC content (<10.5 g kg −1 ) in the topsoil is relatively low, but TN value (0.7–1.6 g kg −1 ) is not so low 11,12,34 . For example, SOC level in the alluvial loess of the North China Plain is lower than in the deposited loess of the Loess Plateau (11.3–11.5 g kg −1 ), but TN is higher relative to those (0.9–1.0 g kg −1 ) in the Loess Plateau 18,34 . Similarly, SOC is lower in the North China Plain relative to Northeast and South China (8.9–25.4 g kg −1 ) with high yields, but TN is comparable (1.0–1.2 g kg −1 for Northeast and South China) 16,17 .…”

“…Our average C:N ratio is close to those (9.7–9.8) reported for the wheat-maize double cropping in Xuzhou, North China and the mono-cropping with maize-wheat-wheat of Urumqi, Northwest China, but slightly lower than those (10.2–10.8) reported for some other parts close to the North China Plain with a variety of cropping systems, e.g., the Yangze River Delta, East China (rice-wheat, rice-rape, wheat-maize cropping and so on), the Loess Plateau in North and Central China (mono-cropping with maize-wheat-wheat and other cropping systems) 18,34,35 . However, soil C:N ratio is considerably lower in our study than those in the black soil with maize cropping (12.3) in Songnen Plain (Northeast China) and red soil with wheat-maize cropping (11.3) in Qiyang (South China) 16,17 .…”

Changes in soil organic carbon in croplands subjected to fertilizer management: a global meta-analysis

“…Both the quantity and the quality of added OM significantly influenced the efficiency of C sequestration37. Both linear15383940 and nonlinear4142 relationships were found between changes in SOC and the amount of organic C added in long-term field experiments and meta-analyses. In this study, the ΔSOC increased linearly with C input in the 10–20 yr, 20–30 yr and 30–40 yr groups (Fig.…”

The impact of alternative cropping systems on global warming potential, grain yield and groundwater use

“…The increase in SOC might be due to the large carbon inputs from crop straw, roots and rhizo-deposition and the low initial SOC level (Huang and Sun, 2006;Yan et al, 2011). In addition to fertilization and straw management (Huang et al, 2013a), the changes in SOC are also dependent on the tillage intensity and cropping system (Tables S1 and S4) (Mosier et al, 2006;Zhang et al, 2010). Net soil carbon sequestration offset part of the positive CO 2 -eq in this study.…”