The Effects Of Culturing Density Of Rice-crab Ecosystem On Rice、crab Growth

Rice-crab culture is the important pattern of the urban circular agriculture and themain direction of developing efficency agriculture in metropolis. However, there has beenlack of in-depth research on this pattern for a long time, especially short of understandingto the influence of the co-culturing density of rice-crab on rice and crab growth. This testmainly aims to select a optimal matching density for rice planting and crab culture in ricefields, through composite design of crab growing density and rice planting density tosynergistically optimize the interaction between these two farming practices, and throughcomparison of yield and quality between rice and crab in different density to explore theoptimal system of rice and crab polyculture, and to reach the double targets of high qualityand high yield of rice and crab. The major results are as follows:1.In the rice-crab co-culture system, the effects of rice planting and crab-culturingdensity on the incidence of larval crab and rice diseases and insect pest as well as grainyields were conducted.The three rice planting densities (spacing in the rows and spacingbetween rows were50cm×60cm、30cm×40cm、10cm×20cm designed for60%，70%，80%of growing area,respectively) and three juvenile crab culturing densities（15kg/hm2，18.75kg/hm2，22.5kg/hm2），each treatment is three replicates. The result showed thatincidence rate of rice diseases, insect pests and crab diseases in rice-crab co-culture systemis far lower than pure larval crab culturing and pure rice planting pattern at the same area.Meanwhile, rice grown in rice-crab co-culture is evaluated as high quality product withoutany chemical pesticide pollution since any chemical pesticides was not permitted to beapplied in the fields,therefore that brought in much higher economic benefitthan tradtionalmonoculture system.2. By comparing rice-crab co-culture with monoculture fields,the amount ofchemical fertilizer (NH4HCO3）applied is significantly reduced by375kg/hm2in the former system than latter during rice growth period since much base manure was applied,thus,only application of tillering fertilizer and panicle fertilizer were enough for rice growth.Meanwhile larval crab waste and crab bait was also able to enrich fertility of soil.3. The effects of rice planting density on the decrease of crab disease incidence andrice diseases and insect pests occurrence rate as well s on the improvement of yields wereinvestigated in rice-crab co-culture fields. In the year2012, the output value of rice-crabco-culture is111750yuan/hm2(profit is97440yuan/hm2); the output value of pure crabis93750yuan/hm2(profit is77085yuan/hm2); the output value of pure rice is15000yuan/hm2(profit is12075yuan/hm2).