Co-culturing rice with aquatic animals enhances soil organic carbon, according to a comprehensive analysis of research to date.
A team of Chinese scientists examined work looking at the farming approach, which is commonly seen across Asia and includes co-culturing rice with fish, amphibians, shrimp and waterfowl. It maximises use of land, water and nutrients, and studies have also shown major added benefits such as improved rice yield and quality, and control of pests and diseases.
With difficulties in assessing its impact on soil carbon from individual trials, the researchers compiled data from 200 papers into a database, which was used to model and analyse the overall effect of this farming technique.
Rice–livestock integration improves soil carbon storage
They found that when compared to rice monocultures, rice-animal co-cultures increased soil organic carbon by an average of 11.6%. However, this varied widely according to what animals were being reared alongside the rice. Amphibians (frogs) had the biggest impact, with a 23.6% increase, with waterfowl, crustaceans and fish at 11.2, 11.1 and 6.8%, respectively.
The growing region and soil type also plays a big role in the level of soil carbon increase, they reported in the journal Science of the Total Environment. Soil organic carbon significantly increased in temperate zones compared to tropical, while there was also a bigger effect in alkaline soils than acidic or neutral.
The type of rice farmed also seems to be crucial. Co-culturing with Japonica rice resulted in 17.5% greater soil organic carbon than with Indica, and indeed, when Indica was cultured with frogs and crustaceans, there was no significant effect on carbon.
A regenerative path for rice production
With paddy fields covering 167 million hectares worldwide, and soil organic carbon representing the world’s biggest carbon pool, changes in practises stand to make a significant contribution to agriculture mitigating climate change. As it stands, two million hectares of farms produce rice alongside animals.
“Given the pressing challenges posed by climate change to agricultural productivity, co-cultures or rice and aquatic animals stand out as a green and efficient agricultural approach,” they said. “Hence, our findings may help design practices that can optimize soil organic carbon accumulation.”
Key takeaways
- New research in southern Brazil shows that integrating livestock into irrigated rice systems increases soil carbon stocks.
- The integrated system added up to 2.6 tonnes more carbon per hectare over 18 years compared to rice monoculture.
- Carbon increases were found across soil layers, with the most significant gains in the top 30 cm.
- Combining crops and livestock could offer climate mitigation benefits while maintaining food production.
- Study supports calls for more regenerative, circular farming practices in paddy systems.
