Science develops practices that reduce greenhouse gas emissions in the cultivation of irrigated rice – Dourados agora

Embrapa has a temperate climate

Research is developed by Embrapa has a temperate climate Over the past 10 years, RS and educational and research institutions in southern Brazil have contributed to the mitigation of greenhouse gas (GHG) emissions from rice production. Several management practices are being implemented and adapted to lowland farming conditions in the Pampa biome, with the aim of balancing the carbon balance, in addition to contributing to increasing water use efficiency, diversifying the production system and identifying rice genotypes most adapted to climate change. The focus has been on the irrigated rice crop in Rio Grande do Sul, which accounts for more than 87% of the country’s total methane emissions in grain cultivation, not to mention the high demand for water.

Among the most relevant practices, alternative water management systems for rice stand out. Intermittent flood and sprinkler irrigation, which replaces continuous flooding, has the potential to mitigate greenhouse gas emissions by more than 70%, in addition to saving water.

The use of nitrogen fertilizers for irrigated rice, based on the use of controlled fertilizers, rather than the traditional soluble sources, is able to reduce emissions of nitrous oxide and ammonia from the rice crop. Ammonia emission factors from various nitrogen sources in irrigated rice cultivation in southern Brazil are significantly lower than the reference indices proposed by the Intergovernmental Panel on Climate Change (IPCC) which is 10%.

Another related result from the research conducted indicates crop diversification, i.e. the introduction of rain-fed crops, such as soybeans (Photo below) and maize, sorghum, and forage alternated with irrigated rice, significantly mitigating the global warming potential of rice monoculture.

One practice resulting from the research that is already fully integrated into the production system is the adequacy of soil and straw management for irrigated rice. Early fall tillage, successive rice harvesting, and soybean rotation reduces the annual global warming potential in the lowlands by more than fivefold. In addition, production systems that incorporate rainfed crop rotations have been established in no tilling Improved pastures, associated with rotational grazing, emit less methane, with a greater potential for soil carbon accumulation, and are therefore recommended as environmentally sustainable alternatives to the lowland environment.

Diversification of Lowland Production: Soybean Cultivation in Rice Areas. take photo: Walkyria Skivitaro

Directing genetic improvement programs and public policies

The R&D measures implemented are directing rice genetic improvement programs towards the development of new varieties that, in addition to grain yield and quality, resistance and tolerance to biotic and abiotic factors, nutritional quality and a lower potential for GHG emissions combine.

They also supported the formulation of public policies aimed at environmental sustainability and minimizing the impact of agriculture on climate change. In this sense, the inclusion of search results in the third and fourth editions of National inventory of anthropogenic emissions and greenhouse gas removalsspecifically in the sectoral report “Methane Emissions from Rice Cultivation”.

In both versions, for the state of Rio Grande do Sul, estimates of methane emissions from rice cultivation were computed using local factors, replacing the data proposed by the IPCC used in previous versions, allowing for a more realistic and positive estimate of the national emissions scenario with respect to irrigated rice crop.

The South and its importance in the national production of rice

Data from the Brazilian Grain Yield Survey made available by the national supply company (Konab) it was found that most Brazilian rice production comes from irrigated crops in Republika Srpska, which although they account for less than 2% of the national area under cereal cultivation, provide more than 70% of the national cereal production. Santa Catarina is another state that traditionally produces irrigated rice. More recently, Tocantins also increased the area under irrigated rice. The three states together account for almost all of the national irrigated rice cultivation.

On the one hand, if the area under irrigated rice cultivation in Brazil remains constant, but with increasing productivity over the years that guarantees national supply, on the other hand, the high rice production, traditionally developed in agricultural frontier areas, the area may decrease year by year, Which makes room for more profitable crops, such as soybeans and corn. This retrospective fact is reflected in national rice production statistics. In 1990, the area cultivated with upland rice in the country was close to 3.1 million hectares (74% of the total); Already in 2021, rain-fed agriculture accounted for 23% of the total area (less than 0.4 million hectares), while the irrigation system totaled 1.3 million hectares (77% of the total).

“These data demonstrate the importance of rice production in Rio Grande do Sul for grain supply and national food security, but also the need and urgency of efforts in research actions so that production is carried out in a sustainable manner, including contributing to the achievement of Brazil’s GHG emission reduction targets that it assumes.” Paris Climate Agreementwhich aims to strengthen the global response to the threat of climate change and strengthen the ability of countries to deal with the effects resulting from these changes, says the researcher.

For her, it is clear that the rotation of rice with rain-fed crops is highly beneficial to lowland production systems in the Republika Srpska, not only by reducing GHG emissions from the irrigated rice crop, but by enabling diversification of production on the property. , in favor of nutrient cycling and integrated pest management, particularly weed control. On the other hand, the introduction of rainfed crops alternating with irrigated rice in the lowlands in general is restricted in technical aspects, highlighting the stress caused by excess water, due to poor soil drainage, and also due to lack of water, which is common in the region during summer. Thus, the success of lowland crop diversification depends on the adoption of additional water management practices, such as soil softening and groove-ridge technologywhich revolutionizes the production of grain, forage and winter cereals in this environment, ”concludes Scivittaro.