In rice-growing regions of southern China, a flooded paddy is often more than a place to grow a single crop. In many rice-duck systems, ducklings are put into the paddy during the early growth stage of the rice and, as a 1999 trial reported in Livestock Research for Rural Development describes, forage between the rows for insects, weeds, and snails. These are called rice-duck and rice-fish co-cultivation systems. The principle behind these systems is straightforward: animals can perform some of the functions traditionally served by herbicides, pesticides, and fertilizers in conventional farming. In many rice-duck systems, the ducks are removed before harvest, so the crop remains intact and farmers get both rice and ducks from one plot of land. Researchers have tested how well the idea works, and the results are less clear-cut than they first appear, especially for pest control by ducks.A 2022 field trial in northern Zhejiang tested ducks against weedsA research team led by Ping Qian published a detailed assessment in 2022 in Biocontrol Science and Technology, based on a suburban farming area in northern Zhejiang. The study, titled Effects of integrated rice-duck farming on weed pressure, herbivore-predator interactions and economic benefits, aimed to evaluate whether conventional farming could be replaced by a farming system with lower chemical pollution. It examined rice-duck farms alongside control and conventional farms in the suburban zone of northern Zhejiang Province during the rice-growing season. The analysis showed that the ducks kept weeds at bay within the paddies. Overall, organic rice-duck technology yielded an economic profit 7.6 times higher than conventional cultivation and 1.4 times higher than the control.Planthoppers increased, and spiders and dragonflies declined in the duck paddiesThe same trial made the story of pest management even more complex. Planthoppers and leafhoppers, both significant rice pests, were more numerous in duck paddies than in either the conventional or control fields. The predators, in particular spiders and dragonflies, were less numerous in the same paddies. The authors suggested that the decline in predators created an “enemy-free space” for herbivores, which may explain the rise in pests. The above-mentioned study found that rice-duck farming was less effective against major insect pests. Nevertheless, the authors suggested the method as a high-return organic farming approach for modern farmers.Qingtian’s carp paddies reflect more than 1,000 years of practiceFish-based systems have a long record in the same region. The FAO’s Agroecology Knowledge Hub states that rice-fish co-culture across southern China dates back more than 1,000 years, and it lists the Qingtian system in Zhejiang Province among FAO’s Globally Important Agricultural Heritage Systems. The hub refers to the system as one that produces rice grain and aquatic protein from the same body of water. It further says that the system efficiently uses the land by producing carbohydrates and animal protein simultaneously.A 2011 field survey found rice-fish paddies used 68 percent less pesticideThe Qingtian tradition was examined in depth in Ecological mechanisms underlying the sustainability of the agricultural heritage rice-fish coculture system, a 2011 paper by Xie and colleagues in the Proceedings of the National Academy of Sciences. The authors describe a system that has persisted for more than 1,200 years, and in their field study the rice-fish plots yielded about the same as mono-cropped rice while using 68 percent less pesticide and 24 percent less chemical fertilizer. The study also found a reciprocal benefit: fish reduced rice pests, rice improved water quality for fish, and nitrogen use became more complementary.
Fish raised in rice paddies can provide an additional source of animal protein alongside the rice crop. Image credits: Wikimedia Commons
The field study done by the authors compared the rice-fish paddies to the rice monoculture and found that the yield and yield stability were the same for both systems. The authors also reported that yield stability matched that of rice monoculture, and that this complementarity in nitrogen use reduced nitrogen loss from the system.What the two studies suggest about sharing the paddy with animalsIn the Zhejiang trial, ducks suppressed weeds but did not control the main herbivore pests, while in the Qingtian field survey, rice-fish plots used substantially less pesticide and chemical fertilizer than rice monoculture, with similar yields. The two findings do not mean that every animal suits every paddy, since results depend on the animal, the pest, and the management practice. The income advantage in the duck trial applied only to paddies with organic certification.
