Changes of soil organic carbon in paddy soils from sixty-five years fertilization experiments

Dr Myung-sook Kim1, Dr Seong-Jin Park1, Dr Sung-Hyun Kim, Dr Hyun-Young Hwang

1National Institute Of Agricultural Sciences, Rural Development Administration(rda), Iseo-myeon, South Korea

Soil organic carbon(SOC) are important for production and quality of rice in paddy soils. Objectives of this study were to assess the changes of soil organic carbon contents during a long-term fertilization experiment on which to base a proper use of fertilizer and soil amendment for a sustainable agriculture in rice production. The changes of organic carbon (SOC) contents in paddy soils (sandy loam) were assessed from data of the 65 years fertilization plots in which the continuous rice cropping experiment started in 1954 at the National Academy of Agricultural Science, Suwon, Korea. The treatments were no fertilization(No fert.), inorganic fertilization (NPK), inorganic fertilizer plus rice straw compost (NPK+C) and inorganic fertilizer plus rice straw compost and silicate fertilizer (NPK+CS). After 33~35 years, SOC content in NPK+C treatment in surface soils (0-15cm) reached at the highest (19 g kg-1), followed by maintaining a plateau level for 8 years. This level was about 1.9 times higher than that (9 g kg-1) of the first 4 years (’54-‘57). The SOC content in No fert. and NPK treatments increased steadily to 13 g kg-1, respectively, which were about 1.3 and 1.4 times higher than those of the first 4 years. After 50 years, however, SOC contents in all treatments tended to decrease and reached in 2018 at 10 g kg-1 in no fert., 12 g kg-1 in NPK and 16 g kg-1 in NPK+C and NPK+CS treatments. Continuous application of rice straw compost and silicate fertilizer affected significantly on the levels of SOC in surface soils. The combined applications of inorganic fertilizers with organic compost and silicate are recommended as the best fertilization practice for fertilizer use efficiency and enhancement of soil fertility status in the continuous rice cropping system in Korea.


I have worked as an agricultural researcher at the National Institute of Agricultural Science in South Korea. Recently I am studying to interpret the changes of soil organic matter in long-term experiment that has been in operation for 65 years in Korea. Attending the SOM Symposium, I hope to share the changes of soil organic matter and broaden the interpretation through different views of other researchers.

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