Abstract
Soil organic carbon and nitrogen are used as indexes of soil quality assessment and sustainable land use management. At the same time, soil C/N ratio is a sensitive indicator of soil quality and for assessing the carbon and nitrogen nutrition balance of soils. We studied the characteristics of soil organic carbon and total nitrogen by investigating a large number of apple orchards in major apple production areas in China. High apple orchard soil organic carbon content was observed in the provinces of Heilongjiang, Xinjiang, and Yunnan, whereas low content was found in the provinces of Shandong, Henan, Hebei, and Shaanxi, with the values ranging between 6.44 and 7.76 g·kg-1. Similar to soil organic carbon, soil total nitrogen content also exhibited obvious differences in the 12 major apple producing provinces. Shandong apple orchard soil had the highest total nitrogen content (1.26 g·kg-1), followed by Beijing (1.23 g·kg-1). No significant difference was noted between these two regions, but their total nitrogen content was significantly higher than the other nine provinces, excluding Yunnan. The soil total nitrogen content for Xinjiang, Heilongjiang, Hebei, Henan, and Gansu was between 0.87 and 1.03 g·kg-1, which was significantly lower than that in Shandong and Beijing, but significantly higher than that in Liaoning, Shanxi, and Shaanxi. Six provinces exhibited apple orchard soil C/N ratio higher than 10, including Heilongjiang (15.42), Xinjiang (13.38), Ningxia (14.45), Liaoning (12.24), Yunnan (11.03), and Gansu (10.63). The soil C/N ratio was below 10 in the remaining six provinces, in which the highest was found in Shaanxi (9.47), followed by Beijing (8.98), Henan (7.99), and Shanxi (7.62), and the lowest was found in Hebei (6.80) and Shandong (6.05). Therefore, the improvement of soil organic carbon should be given more attention to increase the steady growth of soil C/N ratio.
Highlights
China currently has the largest apple cultivation area and production in the world, with 1.99 × 106 ha and 35 × 106 t in the 2011/2012 season [1]
We studied the characteristics of soil organic carbon and total nitrogen by investigating a large number of apple orchards in major apple production areas in China
High apple orchard soil organic carbon content was observed in the provinces of Heilongjiang, Xinjiang, and Yunnan, whereas low content was found in the provinces of Shandong, Henan, Hebei, and Shaanxi, with the values ranging between 6.44 and 7.76 g·kg−1
Summary
China currently has the largest apple cultivation area and production in the world, with 1.99 × 106 ha and 35 × 106 t in the 2011/2012 season [1]. An increasing amount of nitrogen (N) fertilizers are used to improve yield with the corresponding intensive production of fruits. N utilization has already reached 400 kg·hm−2 to 600 kg·hm−2 in Chinese apple orchards, which is four to five times more than that in other countries, and is showing an annual increasing trend [2,3]. Excessive use of N fertilizers cuts down utilization rate and decreases agricultural production benefits, and leads to negative consequences, such as aggravated physiological fruit disease and environmental pollution [4,5,6]. Soil organic carbon and nitrogen are the main nutrition used for vegetation growth, and are used as indexes of soil quality assessment and sustainable land use management [7,8,9]. The superior apple production areas are concentrated in Bohai coast area (Shandong, Hebei, Liaoning, Beijing, Tianjin), OJSS
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