Raising lobsters in paddy fields eliminates the concern of excessive pesticide residues

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In people’s minds, the season when crayfish are widely available is usually in May and June. But in the golden autumn, the crayfish raised by farmers in Xuyi County, Jiangsu Province, in their paddy fields enjoy a bountiful harvest. “\"Rice-shrimp integration\" allows farmers to grow rice while also reaping shrimp, which is a true win-win situation; in some areas, farmers have seen an increase in income of 2,200 yuan per mu as a result. However, many people have expressed concerns about this model that combines planting and breeding. 　　Liu Qiangdong, the founder of JD.com, questioned on his personal Toutiao account: \"There are countless pesticides and fertilizers in paddy fields – can crayfish be eaten?\" ”Many fans also expressed strong agreement in their comments. 　　So, what is the truth? 　　Why are crayfish raised in paddy fields? “Integrated rice-crayfish farming” is an agricultural production method in which crayfish rearing and rice cultivation take place in the same paddy field, enabling a mutually beneficial symbiosis between the two and resulting in a good harvest for both rice and crayfish. ”said Gao Zideng, a Ph.D. from China Agricultural University. 　　Simply put, \"rice-shrimp integrated farming\" involves digging circular ditches about 3 meters wide and 1.2 meters deep around the rice fields. Inside the fields, ditches in the shape of a \"square\" or \"well\" are dug, about 1.5 meters wide and 0.6 meters deep, and these are connected to the circular ditches. After filling these ditches with water, shrimp larvae are placed in them for breeding. 　　In fact, shrimps don’t necessarily have to be raised together with rice. “Crayfish are generally raised in ponds, where aquatic plants need to be planted; the coverage rate of these plants should be no less than 60%. They can also be raised together with a small number of fish. ”Gao Zideng said. 　　However, due to the low profitability of rice cultivation and the high profitability of shrimp farming, integrated farming models such as shrimp farming in paddy fields have emerged to increase the output per unit area of paddy fields. “In this pattern, rice and lobsters benefit from each other: the dense stalks and leaves of the rice plants serve as natural cover for the lobsters, providing them with a suitable environment for shelter, feeding, and growth, while also protecting them from predators such as birds. At the same time, crayfish can help remove weeds from rice fields and provide organic fertilizer. ”Gao Zideng said. 　　Can the shrimp raised in fields be eaten safely? Many people share Liu Qiangdong’s concerns: could these farmed crayfish contain pesticide residues, excessive levels of heavy metals, and other issues? Are they still safe to eat? 　　“Shrimp farming ponds are primarily used for raising shrimp; pesticides that are harmful to the shrimp should not be used, while fertilizers can be applied in moderation. As long as the paddy fields were not contaminated originally, raising shrimp in paddy fields is similar to raising them in ordinary ponds; the shrimp produced do not have excessive levels of heavy metals, so they are definitely safe to eat. ” Xiao Guoying, a researcher at the Institute of Subtropical Agricultural Ecology of the Chinese Academy of Sciences, said. 　　Yan Libo, a senior economist at the Institute of Genetics and Physiology of the Hebei Academy of Agriculture and Forestry Sciences, also believes that since most crayfish are highly sensitive to pesticides, it is not possible to use large amounts of pesticides in paddy fields to control pests, otherwise all the crayfish will die ； Excessive fertilizers that increase rice yields can also destroy the living conditions for lobsters. Therefore, in order to earn the high incomes brought by lobsters, farmers refrain from using pesticides and fertilizers. According to statistics, under the ecological agriculture model of integrated rice and shrimp farming, pesticide use can be reduced by more than 50%, while fertilizer use can be reduced by more than 30%. 　　Gao Zideng pointed out that in the scientific \"rice-shrimp integrated farming\" model, shrimp larvae should be introduced about 10 days after the rice seedlings begin to turn green. If the use of herbicides and bottom fertilizers is properly controlled during this period, their impact on the water quality of the paddy fields can theoretically be reduced to a very low level. Even when pesticides are used in paddy fields, a safety period of over 1 month should be maintained until the crayfish harvesting season, so as to minimize the impact of pesticide residues on the crayfish. In his view, the issue of excessive heavy metals is largely related to the local soil and water resources, and has little to do with the \"rice-shrimp integration\" farming method. 　　Should all paddy fields be used for raising shrimp? According to statistics, the \"rice-shrimp integration\" approach, by creating systems for sequential and simultaneous cultivation of rice and shrimp, can increase rice yields by 5%–8%, while boosting the overall economic benefits per mu by 258%. 　　Since raising shrimp in paddy fields can lead to high yields of rice and ensure a safe source of lobster, should all paddy fields be used for raising shrimp? 　　“The large-scale transfer of land for shrimp farming in paddy fields may lead to an oversupply on one hand, and it undermines the protection of prime farmland as well as reduces the rice production capacity; therefore, widespread adoption should be approached with caution. ”Xiao Guoying further explained that keeping shrimp ponds flooded with deep water for a long time is detrimental to the growth of rice; it often results in underdeveloped root systems, thin stems, few tillers, and lodging at later stages, leading to lower rice yields compared to paddy fields managed normally. At the same time, deep ditches need to be dug around and in the middle of the paddy fields, which is not conducive to their cultivation. 　　Gao Zideng said, “Since the profitability of crayfish farming is 2–3 times that of rice farming, and the field management practices involved in rice production are relatively complex, if those who operate under this model prioritize crayfish over rice, it will lead to a decline in rice yields and quality in some areas, thereby undermining the purpose of integrating rice and crayfish farming to ensure stable rice production and improved efficiency.” ”