稻-鱼种养减控镉及米、鱼性状研究

Effects on rice grains cadmium reduction and the characteristics of rice and fish in rice-fish coculture system

如何在重金属镉(Cd)超标的土壤中生产出质量达标米已成为亟需解决的问题。为探讨稻-鱼种养对大米Cd积累的减控效果,本研究建立了稻(喜两优超占)-鱼(合方鲫2号)种养系统,比较了稻-鱼共作系统和水稻单作系统中环境介质、米、鱼等Cd含量,以及米、鱼的生物学性状。结果显示,稻-鱼共作合方鲫2号平均体重为331.7 g,相比鱼种增重1.7倍。不同种养系统大米的营养品质无显著差异。稻田土壤总Cd平均含量为0.472 mg/kg(pH=5.5),略高于污染临界值0.40 mg/kg(5.5≤pH≤6.5),不同种养系统土壤总Cd含量与土壤pH无显著差异。合方鲫2号内脏虽有少量Cd积累[(0.060±0.032)mg/kg],但肌肉Cd含量很低(<0.003 mg/kg)。水稻单作大米Cd平均含量为0.311 mg/kg,达到国家粮食安全标准限定值的1.6倍。稻-鱼共作大米Cd平均含量仅0.034 mg/kg,较水稻单作大米Cd含量下降89.1%,水稻单作大米Cd含量与土壤总Cd含量呈极显著正相关(r=0.802),而稻-鱼共作系统则无该显著相关性。研究表明,合方鲫2号是适合稻-鱼种养的好品种,以此为养殖品种可以建立完善的稻-鱼综合种养模式,该种模式能有效抑制土壤Cd的生物活性,对大米Cd积累有显著的减控效能,且经济效益显著。本研究为稻-鱼等生态种养综合生产模式的推广应用提供了重要数据支撑和参考。

It is urgently necessary to produce low-cadmium(Cd)rice in Cd-polluted paddy soil.Integrated rice-fishing culture is an efficient complex ecological agricultural production mode,which combines the culture of rice with culture of economic aquatic animals,owning both economical and ecological benefit.In order to investigate the control efficiency on Cd accumulation in rice in the rice-fish coculture system,the newly hybrid crucian carp WR-Ⅱ{[Carassius cuvieri(♀)×C.auratus var.red(♂)](♀)×C.cuvieri(♂)}was used as an example in the rice-fish coculture system,and the cadmium(Cd)concentration in rice grains,WR-Ⅱand environmental medium were compared between the rice-fish coculture system and the rice monoculture system,as well as the quality traits of rice grains and the characteristics of WR-Ⅱwere analyzed.The results showed that the average weight of WR-Ⅱ(331.4±74.3)g in the rice-fish coculture system increased by 1.7 times compared to the fingerling(133.1±22.4)g;there existed no significant difference in the nutrient quality traits of rice grains between the two culture systems;the average value of total soil Cd concentration(0.472 mg/kg,pH=5.5)was a little higher than the pollution threshold(0.40 mg/kg,5.5≤pH≤6.5),and there was no significant difference observed in the total Cd concentration in paddy soil and in the soil pH between the two culture systems;a low level of Cd accumulation(0.060±0.032)mg/kg was found in viscera of the WR-Ⅱ,while this value in fish muscle was lower than the minimum detection limit value(0.003)mg/kg for Cd;the average Cd concentration in rice grains in the rice monoculture system was 0.311 mg/kg(0.239-0.381)mg/kg,reaching 1.6 times of National Food Safety Standards Limits of Cd for Foods in China(0.2)mg/kg;while this value(0.034)mg/kg in rice grains in the rice-fish coculture system was much lower than 0.2 mg/kg,and was down 89.1%compared to that in rice monoculture system;there was significantly positive correlation(P<0.01,r=0.802)between the Cd concentration in rice grains and total soil Cd concentration in rice monoculture system,but not in rice-fish coculture system.Our results indicated that the WR-Ⅱwas a great species for rice-fish coculture system,which can inhibit the biological activity of Cd in soil,and in turn effectively reduced the rice in Cd uptake in this system,yielding low Cd and quality rice grains and fish,as well as outstanding economic benefits.The results of this study provide useful guidance and important data on Cd accumulation in rice for the promotion and development of integrated farming of rice and fish.