Many traditional agricultural systems have been created, shaped, and maintained by generations of farmers and herdsmen who have used locally adapted practices to manage diverse natural resources. Recognizing the ecological legacy in these traditional agricultural systems may help us develop novel sustainable agriculture. Here, we describe how a traditional rice-fish system, which has been designated a “globally important agricultural heritage system”, has been maintained for over 1200 years in southern China.
We first conducted a 6-year study to examine how the rice-fish system can maintain the same rice yield stability as rice monoculture with a low input of pesticides and chemical fertilizers through a long-term experiment with three treatments: rice monoculture (RM), rice-fish co-culture (RF), and fish monoculture (FM). We then conducted another 5-year study to determine how this rice-fish system preserves high genetic diversity of a local common carp, which is locally referred to as “paddy field carp” (PF-carp), and how genetic diversity benefits the whole system.
Results/Conclusions
In the first study, field survey showed that RF maintained the same rice yield and stability as RM but required 68% less pesticide and 24% less chemical fertilizer than RM. The experiment further confirmed that the temporal stability of rice yield is higher in RF than in RM in the absence of pesticide application. We found that this higher stability of rice yield with low pesticides and chemical fertilizers in RF is associated with positive interactions between rice and fish. On the one hand, fish benefitted rice by reducing insect pests by 45%, diseases by 38%, and weeds by 90%. On the other hand, the reduced input of N fertilizer in RF can be explained by complementary N use by rice and fish. In the second study, molecular analysis showed that the PF-carp has high genetic diversity and diverse color-phenotypes. Video-recording technology showed that the color-phenotypes differed in feeding activity. Stable isotope analysis (SIA) of 13C and 15N showed that the color-phenotypes had different values of δ15N and δ13C. The analysis of Stable Isotope Bayesian Ellipses in R (SIBER) also showed a separation of isotope niche, indicating that the color-phenotypes differed in using food resources. Field experiment further showed the mixed culture of color-phenotypes within a field resulted in an over-yielding of PF carp population. Study of the rice-fish system suggests that ecological principles used in traditional agricultural systems could be referred in the design of modern agriculture.