Effects of fertilization on soil organic carbon and distribution of SOC in aggregates in tidal flat polders
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    Abstract:

    Soil organic carbon (SOC) content has long been recognized as an important indicator of soil quality. Soil aggregates are considered as the basic structure of soil. Soil aggregation and SOC accumulation are interrelated: SOC or its fractions are basic to aggregation process, whereas SOC sequestered within aggregates is protected against decomposition. This relationship between aggregates and SOC is considered as an important mechanism of physical protection of SOC. A number of studies have been conducted by scientists at home and abroad, focusing on distribution of SOC in aggregates in paddy soils, black soils, and degraded soils. However, few have reported about effect of fertilization on SOC distribution in aggregates in coastal saline soil. In this paper, an experiment was carried out in a field of coastal saline soil in North Jiangsu, to study effects of fertilization on soil organic carbon and SOC distribution in aggregates various in size. The experiment was designed to have four treatments: no fertilizer (CK), farm yard manure (FYM), commercial organic fertilizer (COF) and inorganic fertilizer (IF), and three replicates for each treatment. Soil samples were collected from the 0~10, 10~20, 20~30, 30~40, 40~60, 60~80, 80~100 cm soil layers, and then air-dried, and ground to pass a 0.15 mm sieve for determination of soil organic carbon with the oxidation method using potassium dichromate in 0.4 mol L-1 K2CrO7-H2SO4 solution. Distribution of water-stable aggregates was measured according to Haynes (1993). Analysis of variance producers were conducted using the SPSS statistical procedures. Results show that all the treatments were obviously higher than CK in content and density of soil organic carbon in the 0~30 cm soil layer, with Treatment FYM, in particular, which increased the content and density by 0.66 g kg-2and 0.07kg m-2, respectively. The water-stable aggregates in the studied field were dominated by those >5 mm and 0.25~0.5 mm, in particle size, which accounted for 37%~57% and 13%~20%, respectively. The fraction of >5 mm decreased in content, while the fraction of 0.25~0.5 mm increased along with soil depth in all the treatments. Treatment FYM significantly increased the content of the fraction of >5 mm, but decreased that of the fraction of 0.25~5 mm significantly. Distribution of SOC in aggregates was found to be that in aggregates varying from 0.5~1 mm to >5 mm in particle size, the smaller the aggregates, the higher the SOC content therein. The fraction of 0.5~1 mm size was the highest (6.83 g kg-1) in SOC content. Compared with all the other treatments, Treatment FYM increased SOC content in all the fractions of aggregates. In the experiment field, SOC content in the soil was a positively related to that in the fraction of >5 mm (p <0.01), and negatively to that in the fraction of 0.25~5 mm (p <0.01 or p >0.05).

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Hou Xiaojing, Yang Jingsong, Wang Xiangping, Jin Wenhui, Yao Rongjiang, Yu Shipeng. Effects of fertilization on soil organic carbon and distribution of SOC in aggregates in tidal flat polders[J]. Acta Pedologica Sinica,2015,52(4):818-827.

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History
  • Received:October 14,2014
  • Revised:March 04,2015
  • Adopted:March 12,2015
  • Online: April 24,2015
  • Published: