Objective   Organic matter contents in the latosolic red soils under various long-term fertilization practices were measured to analyze the effects and to establish a prediction model for efficient management.

  Method   Two long-term experiments were conducted on separate uplands in Fujian of peanut-sweet potato rotating cultivation fields with latosolic red soil. The designated lots were under either a continuous application of different chemical fertilizers for 16 years or of chemical/organic fertilizations for 14 years. Content of soil organic matters (SOM) was monitored, and a grey prediction model constructed based on the collected data.

  Result  The fertilizations boosted SOM content in the soils in comparison to the lot without fertilizer application. The use of the Recommended Fertilizer (RF) increased the average SOM to (19.83±0.77) g·kg⁻¹, which was significantly higher than the applications of other chemical fertilizers. The content further increased to (22.53±1.69) g·kg⁻¹, i.e., 2.8 times of RF treatment on an annual basis, when the chemical/organic manure combination (RF+OM), especially the decomposed pig manure (RF+PM), was applied. The grey prediction model on SOM yielded fitting errors ranging from 1.226% to 3.307% for all fertilizations. While the predicted result of the non-fertilization was on a continuously downward trend, and the RF treatment increased to (20.220±0.002) g·kg⁻¹, which was superior to all other fertilizations using chemicals. More important, the long-term SOM would be on a increasing trend under chemical/organic fertilization, especially RF+PM that ranked the top among all treatments reaching the significantly higher level than RF at (23.777±0.017) g·kg⁻¹.

  Conclusion  Based on the past records and the predicted trend on SOM, RF undoubtedly improved the fertility of the latosolic red soil. However, RF+OM, especially RF+PM, would bring even more impressive results, and thus deserved serious consideration for the agricultural practice in the area.