Rice fields are ecosystems that support the growth and production of aquatic organisms. The integrated cultivation of rice and fish can be likened to symbiosis in which the fish increase rice production by providing access to nutrients (bioturbation, faeces, pest control) and the rice provides food for the fish.
In combination with rice cultivation, fish farming allows agricultural intensification by improving labour productivity and overall yield. In rice fields, fish farming optimizes the use of land and water resources and improves the fertility of plots. In addition, by consuming algae and weeds (parasitic plants), fish help to reduce competition with rice and can greatly reduce, if not eliminate, the need for chemical pesticides such as herbicides, insecticides and molluscicides. The need for supplementary feeds for the fish is reduced by the natural richness of the rice ecosystem in phytoplankton, zooplankton, macrophytes, benthos, detritus and bacteria, also limiting the risk of disease (Halwart et al., 2014).
Despite the advantages of this production system, this aquaculture practice is still very little developed in Cambodia. A survey will be carried out, on the one hand, to clarify the perception and representations that this activity generates among stakeholders and, on the other hand, to identify the factors mentioned by rice farmers as the reason for the low appropriation of rice-fish farming.
The AquaCAM project also proposes to carry out production pilots at volunteer farmers’ sites, financing, in particular, the scientific component of the studies (nutrient flows, stable isotopes, water analyses). The natural abundances of stable isotopes of carbon and nitrogen (δ13C and δ15N) commonly used in ecology, will allow characterizing the trophic functioning of these rice fields
Pilots at A Siem Reap
Within the framework of AquaCAM and with the new project partner APDRA, the objective of the pilots conducted with fish farmers in this province is to promote ecological intensification of rice cropping systems towards more diversified and productive rice-aquaculture systems.
This innovation could double rice yields and of course, guarantee improved fish production, which will be produced in association with rice or rotation. In the dry season, the rice fields-which are not yet in production-are swarmed with climbing perch (Anabas testudineous) fry. This fish was selected for its rapid growth and its ability to breathe atmospheric air, allowing it to survive and grow in low oxygen environments. The production of this fish, without any exogenous feeding, could reach 3 tons/hectare per cycle. Moreover, this fish is appreciated by the consumer and the systematic harvesting of this fish also allows valorizing at best the collection of wild fish which also have a very high nutritional value.
From April to July, during the rainy season, traditionally produced rainfed rice (Romdoul) will be combined with silver barb (Barbonimus gonionotus). These fish will be stocked and cohabit with wild fish recruited spontaneously in the rice fields. The fish are grown in the rice field during the flood period and then in the prepared refuge ditches on one side of the rice field. Without further communication, the rice field will be sown with high-yielding, fast-growing rice (HVY), which will be harvested with the fish two months after sowing. This innovation could produce up to 3 tons per hectare per cycle of silver barb, two tons of Romdoul rice, and 4 tons of HYV rice without further inputs.
Pilots in Takeo
In Takeo Province, where rice farmers have more favourable agronomic conditions, the objective of the trials set up is to increase the economic gain from fish farming by integrating high-value freshwater shrimp (Macrobrachium spp.) into the traditional rice-wild fish system. The integration of freshwater shrimp into the rice-fish farming system is expected to increase rice production yields and farm profitability, but also to have a positive impact on soil nutrient release.
In addition, the introduction of this economically valuable species will encourage more rational use of chemicals and promote integrated pest management (IPM) approach, with economic and environmental gain by enhancing the beneficial effects of ecosystem services. Expected yields are in the order of 1.5 tons/ha/cycle for shrimp and 1.5 tons/ha/cycle for rainfed rice. These trials will be coordinated by FiA.
To verify the success of these trials, the pilots in Siem Reap and Takeo will all be carried out with rice field controls and are scientifically coordinated by CIRAD experts, notably in the field by Dr Kazi Kabir.