Success Stories In Asian Aquaculture - Library - Network of ...

32 M. Weimin2.9.3 Contribution to Environmental IntegrityEnvironmental sustainability is attracting increasing concern worldwide in the newmillennium. Development of rice–fish culture in China has contributed significantlyto the environmental integrity.2.9.4 Minimizing Environment Impacts Through Least Useof Chemicals and DrugsOrdinary rice cultivation and intensive fish culture often involve use of a range ofchemicals and drugs for the control of diseases, pests/parasites, and weeds. Theuse of large quantities of chemicals and drugs not only affect the quality of theproduct, but also cause adverse impacts on the environment with residues addedto water and soil. Rice–fish culture creates a symbiotic system where fish play aneffective role in the control of pests and diseases of rice in the system. Experimentsand production practices have shown that incidence of rice diseases/pests is significantlyreduced in rice–fish culture systems (Table 2.2 ). The application ofpesticides can be lowered by 50% of that of modern high-input rice production;sometimes, no pesticide application is required ( Lu and Li 2006) . Fish and otheraquatic animals also help in weed control of the system. For example, when 1 kgof grass carp is produced in a rice field, about 80 kg of weed is consumed by fish(Zeng and Wang 2006) . As a result, the use of pesticides and herbicides is significantlyreduced in rice–fish culture system. Herbicide is only used before thetransplantation of rice and weeding throughout the rice growing period is notnecessary.On the other hand, incidence of fish diseases is also considerably reducedcompared with other aquaculture systems, particularly in pond culture. This islargely due the feature of the rice system.Hence, the environment impacts involved in rice and fish production are minimal ifnot zero, while producing high quality rice and fishery products. Hardly any other foodproduction system can be compared with rice–fish system in this regard.Table 2.2 The effect of bio-control of rice pests and disease in rice–fish ecosystemsRice treatmentRice planthopperNarangaaenescensMoore parnaraguttataRice leafrollerRice leafhopperSheathrot (%)Monoculture 237 534 20 11 839 37.7Rice–fish 75 107 10 6 227 4.9Unit: head/patch −1 (number of pest in one testing patch) (Lu and Li 2006)