Objective To explore the change of soil quality under long-term low input rice-fish co-culture mode.

Method After constructing the minimum data set (MDS) and scoring linearly the indexes, the soil quality of rice-fish co-culture for 15 years (FR15) or 50 years (FR50) was evaluated using soil quality index (SQI).

Result The results of descriptive statistics showed that the contents of total nitrogen and organic matter were rich, the contents of total phosphorus, available phosphorus and available potassium were moderate, and the content of total potassium was insufficient. The indexes of total nitrogen, total potassium, total copper and total magnesium contents and pH were selected to construct the MDS. The SQI value of MDS had a significant linear positive correlation with that of the whole dataset, and could be used to evaluate soil quality. Total nitrogen content contributed the most to soil quality evaluation (The contribution percentage was 26.50%), followed by total copper (23.01%), total potassium (19.23%), total magnesium (16.50%) and pH value (14.76%). Compared with rice monoculture, the SQI value of FR15 significantly decreased by 27.90% and FR50 increased by 18.23%.

Conclusion Although soil quality of the long-term low-input rice-fish co-culture model will be reduced due to material input, with the continuous extension of the system maintenance time, the nutrient utilization rate will be improved, and soil quality can be significantly improved and maintained stable.