عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Fish culture in rice field is an ancient activity in Asia and probably it has been a routine activity in China since decades ago. Countries are now gradually finding out the advantages of the activity putting more and more land under the integrated culture. The integrated culture was first conducted in 1983 in Iran. Since then, the activity has been extended in the rice fields of 11 provinces of the country. In an experimental project in 2003, 13 rice fields totally covering 8.2 hectares and 13 control fields with the same size, physical and chemical conditions were chosen to investigate the outcomes of the integrated culture. For this, 1400 specimens of juvenile fish each weighting on average 35-45 grams and composed of 57% common carp, 29 % grass carp, 14% silver carp and big head carp were stocked per hectare of each field. The average weight for grass carp individuals was 25-35 grams. Feeding rate was based on the fish biomass. In harvesting time, characteristics of the rice were compared between experimental and control fields in order to determine the quality and quantity changes in the product. At the same time, usage of fertilizer, pesticides and herbicides were measured in both experimental and control fields. The pesticide usage in control fields was 15 kg per hectare, but in experimental fields it was only 5kg per hectare. This showed 66% reduction in pesticide use. In each control field, 2 liters of herbicides was used, as compared to only 0.3 liter per hectare in the experimental fields, showing an 85% percent reduction. The chemical fertilizer (urea, phosphate, potassium) used in the control fields was 169 kg per hectare, translating into a 23% reduction in each experimental field. Overall, rice production increased302 kg per hectare in the control fields. In this experiment, the profit of fish and rice integrated farming was estimated to be 4,300,000 Rials (US$505). The results showed that enhancing fish and rice integrated farming might increase farmers' profits; while reducing the need to apply fertilizers and pesticides.