Growing Rice with Aquatic Animals Increases Output & Reduce Chemical Use

Growing rice alongside aquatic animals can reduce the need for chemical fertilizers and pesticides while increasing farmer yields, according to a study published today in the journal eLife. The findings point to a method for reducing the environmental harms associated with rice production, as well as potential economic benefits for rice farmers.

Findings of Study:

Modern farms frequently grow only one type of crop, necessitating large amounts of fertilizer and pesticides. This has aided crop production but at the expense of greater environmental degradation. Some farmers are experimenting with growing a mix of crops and animals in order to reduce the need for agricultural chemicals by taking advantage of beneficial plant-animal interactions.

"One example is farmers experimenting with growing aquatic animals in rice paddies," says co-first author Liang Guo, Postdoctoral Fellow at Zhejiang University's College of Life Sciences in Hangzhou, China. "Learning more about how these animals contribute to rice paddy ecosystems could help with more sustainable rice production."

Guo and colleagues conducted three four-year experiments to compare rice growth with carp, mitten crabs, or softshell turtles to rice growth alone. They discovered that aquatic animals reduced weeds, increased organic matter decomposition, and increased rice yields when compared to rice grown alone.

"We also found that nitrogen levels in the soil remained stable in rice paddies with aquatic animals, reducing the need for nitrogen-based fertilizers," says co-first author Lufeng Zhao, a Ph.D. student at Zhejiang University's College of Life Sciences.

The researchers then looked into what the animals ate in the rice paddies. They discovered that plants and other materials they scavenged made up 16-50 percent of their diet, rather than their feed. They also discovered that rice plants used approximately 13-35 percent of the nitrogen from leftover feed that was not consumed by the animals.

Growing rice with aquatic animals resulted in yields that were 8.7 to 12.1 percent higher than yields from rice grown alone. Farmers were also able to grow between 0.5 and 2.5 tonnes of crabs, carp, or turtles per hectare in addition to rice.

"These findings improve our understanding of the roles of animals in agricultural ecosystems and support the view that growing crops alongside animals have a number of advantages," says Xin Chen, Professor of Ecology at Zhejiang University's College of Life Sciences and co-senior author of the study with Dr. Liangliang Hu and Professor Jianjun Tang.

"In terms of rice production, adding aquatic animals to paddies may increase farmers' profits because they can sell both the animals and the rice, allowing them to spend less on fertilizer and pesticides, and charge more for sustainably grown products."

(Source: eLife)