Rice polyculture is the cultivation of rice and another crop simultaneously on the same land. The practice exploits the mutual benefit between rice and organisms such as fish and ducks: the rice supports pests which serve as food for the fish and ducks, while the animals' excrement serves as fertilizer for the rice. The result is an additional crop, with reduced need for inputs of fertilizer and pesticides. In addition, the reduction of pests such as mosquito larvae and snails may reduce mosquito-borne diseases such as malaria and dengue fever, and snail-born parasites such as the trematodes which cause schistosomiasis. The reduction in chemical inputs may reduce environmental harms caused by their release into the environment. The increased biodiversity may reduce methane emissions from rice fields.
Common carp may have been the first fish in rice-fish systems.
Indian Runner ducks with free access to rice paddies in Bali, Indonesia provide additional income and manure the fields, reducing the need for fertilizer.
In agriculture, polyculture is the practice of growing more than one crop species together in the same place at the same time, in contrast to monoculture, which had become the dominant approach in developed countries by 1950. Traditional examples include the intercropping of the Three Sisters, namely maize, beans, and squashes, by indigenous peoples of Central and North America, the rice-fish systems of Asia, and the complex mixed cropping systems of Nigeria.
Pawpaw trees growing under mulberry trees, a forest gardening style of polyculture
A Central American polycultural "milpa" in 2011. Beans are growing among the drying maize; banana trees are in the background.
Excellent soil structure in land in South Dakota farmed without tillage using a crop rotation of maize, soybeans, and wheat accompanied by cover crops. The main crop has been harvested but roots of the cover crop are still visible in autumn.
Applying pesticides to crops in a monoculture: polycultures need lower inputs, reducing environmental harms.