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In long run whether the use of chemical fertilizers could be reduced and soil fertility could be maintained through rice-fish co-culture is less well known.At pilot site of the rice-fish co-culture system which is one the five "globally important agricultural heritage systems" (GIAHS), we conducted a 4-y study to compare fertilizer use, rice yield, and soil fertility in rice-fish co-culture and rice monoculture.Based on survey data from 21 villages, rice yield did not differ between rice monoculture and rice-fish co-culture but less chemical fertilizers was used in rice-fish co-culture than in rice monoculture.Survey data from 145 farms also showed that rice-fish co-culture farms with high input of feed for fish used less chemical fertilizers for rice production than farms with low input of feed for fish.In the 4-y field experiment, although less fertilizer was used in rice-fish co-culture, rice yield, soil organic matter, soil total nitrogen, and soluble phosphorus did not differ between rice-fish co-culture and rice monoculture.Our results suggest that rice-fish co-culture can reduce chemical fertilizers application, enhance productivity of the land, and maintain soil fertility.Our results also suggest that rice-fish co-culture could reduce the risk of non-point source pollution by reducing the input of chemical fertilizers.