Abstract: A long-term (1982-2010) field experiment was conducted in the Red Soil Experiment Station of Chinese Academy of Agricultural Sciences in Qiyang County of Hunan Province, South-central China to investigate the dynamic changes of rice yield and soil organic matter (OM) and nitrogen contents under different fertilization treatments. The treatments included NPK, NPKM (M: manure), NPM, NKM, PKM, M, and CK. Fertilization increased the soil OM, total N, and alkaline-hydrolysable N contents and the rice yield. In treatment NPKM, the rice yield across the 28 years maintained at the highest level; while in treatment NPK, the yield showed a decreasing trend, being lower than that in other fertilization treatments. In the treatments applied with manure only or in combining with chemical fertilizers, the soil OM content increased rapidly in the first 16 years, and then fluctuated around a constant level (29.42-39.32 g·kg^-1). In the treatments of chemical fertilization, the soil OM content only had a quicker increase in the first 8 years, and then fluctuated within a relatively stable range. Fertilization with manure increased the soil OM significantly, as compared to fertilization with chemical fertilizers only. The soil total N content in all fertilization treatments showed a rapid increase in the first 8 years, and the increment was the highest in treatment NPKM. The soil alkalinehydrolysable N content in all fertilization treatments had a slower increase in the first 12 years, with an average annual increment of 0.66-2.25 mg·kg^-1·a^-1. In 1994-1998, the soil alkalinehydrolysable N content in fertilization treatments had a quicker increase, with an average annual increment of 6.45-32.45 mg·kg^-1·a^-1; but after 1998, the soil alkalinehydrolysable N content had a slight decrease. It was concluded that organic fertilization was the key measure to stably improve the physical and chemical properties and the productivity of red paddy soils by increasing their OM and nitrogen contents, and to sustain the rice production in red soil region in subtropical China.

Key words: long-term fertilization, rice yield, soil organic matter, soil nitrogen, dynamic change.