Coculturing rice with aquatic animals promotes ecological intensification of paddy ecosystem: a review

Species coculture can increase agro-biodiversity and therefore constitutes an ecological intensification measure for agriculture. Rice-aquatic animal coculture, one type of species coculture, has been practiced and researched widely. Here, we review recent studies and present results of a quantitative analysis of literature on rice–aquatic animal coculture systems. We address three questions: (i) can rice yield and soil fertility be maintained or increased with less chemical input through rice-aquatic animal coculture? (ii) how do aquatic animals benefit the paddy ecosystem? (iii) how can coculture be implemented for ecological intensification? Meta-analysis based on published papers showed that rice-aquatic animal cocultures increased rice yield, soil organic carbon, and total nitrogen and decreased insect pests and weeds compared to rice monocultures. Studies also showed that rice-aquatic animal cocultures reduced pesticide and fertilizer application compared to rice monocultures. Rice plants provide a beneficial environment for aquatic animals, leading to high animal activities in the field. Aquatic animals, in turn, help remove rice pests and act as ecological engineers that affect soil conditions, which favor the growth of rice plants. Aquatic animals promote nutrient cycling and the complementary use of nutrients between rice and aquatic animals, which enhances nutrient-use efficiency in the coculture. To generate beneficial outcomes, how to develop compatible partnerships between rice and aquatic animals, and compatible culturing strategies for coculture systems are the key points. Investigating which traits of aquatic animals and rice varieties could best match to create productive and sustainable coculture systems could be one of the future focuses.