Text: Editorial*
Rice is one of the most widely consumed foods in the world, and it is essential for the food security of millions of people. However, traditional rice growing in constantly flooded areas is associated with high emissions of methane (CH4), a greenhouse gas that contributes significantly to global warming. Now, a pioneering study led by researchers from USP’s School of Agriculture, “Luiz de Queiroz” (Esalq), in partnership with Embrapa and with international support from the University of Florida, is changing this scenario.
Using the world’s most widely used agricultural model, DSSAT, a team of Brazilian scientists explored irrigation management alternatives that could optimize rice cultivation. For the first time, the DSSAT model was tested to simulate methane emissions in rice systems under different irrigation practices in subtropical conditions in Brazil. In addition, the researchers improved the model’s code, adjusting parameters related to the soil and the water cycle. This allowed for greater precision in the simulation of emissions under specific conditions, such as intermittent and sprinkler irrigation.
Sustainable alternatives for growing rice
Embrapa performed the field study over four consecutive growing seasons (2019-2023) in the Capão do Leão region of Rio Grande do Sul. During this period, the scientists tested two main water management practices: flood irrigation or intermittent irrigation.
The results showed that intermittent irrigation can reduce methane emissions by up to 80%, depending on soil conditions, without harming rice productivity. This technique, widely studied in other countries, was adapted to the specific conditions of Brazil’s subtropical areas, with soils characterized by high density and low natural drainage.
This study also evaluated sprinkler irrigation as an even more sustainable alternative. In long-term scenarios, simulating 30 years of historical climate data, the researchers found that sprinkler irrigation, triggered when the soil reaches 50% of its available water capacity, showed the best results. This practice not only significantly reduced methane emissions but also saved water and maintained high levels of productivity.
The water-methane productivity index (CWMP), developed by researchers to measure water use efficiency, productivity, and emissions, showed that sprinkler irrigation was 52% more efficient than traditional systems. This represents a considerable step forward for sustainable rice production, especially given climate change and scarce water resources.
In addition to the practical results, the study was a scientific milestone. The team of scientists used DSSAT to explore these issues and made fundamental adjustments to the model’s code, including calibrating it to simulate methane emissions in non-flooded conditions, something that had never been done before. These adjustments included optimizing parameters such as soil regeneration after drainage and the fraction of pores filled with water that activates methane production.
These scientific results have global implications, as they provide a solid scientific basis for using agricultural models as a tool for managing the impact of management practices on the sustainability of agricultural systems, not only in Brazil but also in other subtropical and tropical regions. Collaboration with international institutions, such as the University of Florida, reinforces the study’s relevance on the global stage. This study was funded by the São Paulo Research Foundation (Fapesp).
To read the full article, visit this link.
*Evandro H. Figueiredo Moura da Silva, via Esalq’s Communications Office
English version: Nexus Traduções
