Nutrient removal ability and economical benefit of a rice-fish co-culture system in aquaculture pond.

Integrated culture of fish with crops has gained increasing attention to remediate the nutrients pollution of aquaculture. However, rice-fish co-culture system has rarely been investigated. In this study, we constructed a rice-fish co-culture system in the pond by using a new high-stalk rice variety, and conducted an on-farm experiment to examine the nutrients removal efficiency and economical benefit of this system. The results showed that this system significantly reduced the nutrients levels in the water and bottom soil in pond comparing with fish monoculture. The contents of total nitrogen (TN), ammonia-N, nitrate-N, nitrite-N, total phosphorus (TP) and orthophosphate (OP) were 70.63%, 60.27%, 54.86%, 71.54%, 85.05% and 78.54% lower in the water of rice-fish co-culture than fish monoculture pond, respectively. And the contents of ammonia-N, TP and OP in the bottom soil were also respectively reduced by 91.14%, 36.99% and 58.57% under rice-fish co-culture system. The total cost was only increased by 2.88%, but the net income was enhanced by 114.48% for rice-fish co-culture than fish monoculture, which was primarily attributed to extensive rice cultivation. These results suggested that rice-fish co-culture in pond was an efficient method to mitigate the eutrophication in an intensive culture pond, and also a potential new way to increase rice production for food security and extra income for fish farmers.