Agricultural climate risk zoning for sunflower is updated in Brazil

The Ministry of Agriculture, Livestock and Supply (Mapa) published this Wednesday (16/06) Ordinances No. 176 a 202, which update the Agricultural Climate Risk Zoning (Zarc) for sunflower cultivation in Brazil. Zarc is a risk analysis tool derived from climate variability that takes into account crop and soil characteristics.

“In the case of sunflower, we defined the areas and sowing periods for its cultivation with probabilities of yield losses of less than 20%, 30% and 40%, due to the occurrence of adverse weather events”, explains researcher José Renato Bouças Farias, from Embrapa Soja. 

Studies for the development of the new version of Zarc for sunflowers began in 2020 and were validated in meetings held with the main actors in the sunflower production chain in May 2021. To update Zarc, Embrapa researchers employed new methodologies, expanding the climate risk zoning of sunflower for all of Brazil. New risk factors were considered, associating water, thermal and phytosanitary issues.

“A new methodology for addressing risks associated with water available in the soil was also introduced, leaving it ready to incorporate new concepts of soil management and production systems to be associated with climate risk in future zoning work”, explains Farias .

According to the researcher, the sunflower is little influenced by variations in latitude and altitude, has tolerance to low temperatures and is relatively resistant to drought. Regarding the water needs for sunflower cultivation, Farias states that the ideal would be around 500 to 700 mm of water available, well distributed throughout the cycle. “The phases most sensitive to water deficit occur during sowing and plant emergence and, mainly, from the beginning of bud formation to the beginning of flowering followed by the formation and filling of grains”, highlights Farias.

Another factor considered as one of the parameters in Zarc was the association of climatic conditions with phytosanitary risk, since the climate may or may not favor the development of important diseases that are difficult to control. White rot, caused by the fungus Sclerotinia sclerotiorum, for example, it is associated with cold, wet conditions. On the other hand, alternaria spot, caused by the fungus alternaria helianthi, is due to high temperatures and excessive rainfall. “Our study also sought to delimit areas and identify periods of lower climatic risk for the occurrence of phytosanitary problems and, thus, favor the exploration of sunflower cultivation in Brazil”, he highlights. 

Data base

The meteorological database used in the Zarc update is made up of historical series of approximately 30 years, obtained from the networks of terrestrial, meteorological and pluviometric stations, conventional and automatic, of the National Institute of Meteorology (Inmet), of the HidroWeb system, operated by the National Water Agency, and those belonging to the Weather Forecasting and Climate Studies Center (CPTEC/INPE), in addition to state networks maintained by public institutions or companies.

“The rainfall series gathered and with data periods from 1980 onwards, underwent a homogeneity test and consistency analysis and include around 3.500 data points distributed across the national territory”, he explains. “The maximum and minimum temperature data used comes from the base generated by interpolation from 735 meteorological stations”, states Farias.

Sunflower culture 

Sunflower can be grown from Rio Grande do Sul to Roraima. The National Supply Company (Conab) estimates that the area cultivated in Brazil in 2021 will be 31,5 thousand ha, 70% of which will be in the state of Goiás (around 20 thousand ha), followed by Mato Grosso (8,5 thousand ha), Rio Grande do Sul (1,5 ha), Minas Gerais (800 ha) and the Federal District (700 ha).

Despite the diverse uses of sunflower and the crop's potential as a component of diversified and profitable production systems, Farias explains that variability in water availability is the main limitation to the expression of sunflower's yield potential in Brazil.