[Soil organic carbon sequestration rate and its influencing factors in farmland of Guanzhong Plain: a case study in Wugong County, Shannxi Province].

Take Wugong County as an example, soil carbon storage and soil carbon sequestration rate were calculated, the change law of farmland soil organic carbon was explored, and the relationship of farmland soil organic carbon and natural factors, human factors was further revealed. The results of the study showed that: (1) The soil organic carbon contents in 80% of the sampling sites were in the range of 8.0-12.0 g x kg(-1), and the organic carbon contents in 0-20 cm soils showed a normal distribution. (2) In 2011, the organic carbon density of the 0-20 cm farmland soil was 26.3 t x hm(-2), below the national average soil organic carbon density (33.45 t x hm(-2)) of the arable layer. In the last 30 years, the soil carbon sequestration rate in the 0-20 cm layer was 71.3 kg x (hm2 x a)(-1), and in the past five years, the carbon sequestration rate was 480 kg x (hm x a)(-1). The recent carbon sequestration rate was higher than the national average soil carbon sequestration rate of the arable layer [380.78 kg x (hm2 x a)(-1)]. (3) In the semi-humid plain region, soil organic carbon was mainly affected by soil types, landform types, organic fertilizer. Soil types accounted for 30.2% of the organic carbon variability; the landform types and the organic fertilizer could explain 37.7% and 32.1%, respectively. The results of the comprehensive analysis showed that the farmland soil organic carbon density of Wugong County in the past 30 years is increasing, and this probably relies on the utilization of chemical fertilizer and the returning straw. Further study should be conducted on the impact of the chemical fertilizer and returning straw.