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The Ministry of Agriculture published this Wednesday (16) Ordinances No. 176 to 202, which update the Agricultural Zoning of Climate Risk (Zarc) for sunflower cultivation in Brazil. The tool indicates the best planting time for the crop, reducing the possibility of losses due to the weather, considering soil conditions and the characteristics of the crop.
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Studies for the new Zarc began last year and were validated within the production chain. “We defined the areas and sowing periods for its cultivation with probabilities of yield losses lower than 20%, 30% and 40%, due to the occurrence of adverse meteorological events”, explains researcher José Renato Bouças Farias, from Embrapa Soja.
New risk factors were considered, associating water, thermal and phytosanitary issues. 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, is associated with cold, damp conditions. On the other hand, alternaria spot, caused by the fungus Alternaria helianthi, is a result of 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.
Zarc is based on historical series of approximately 30 years, obtained from networks of terrestrial, meteorological and pluviometric stations, conventional and automatic, in addition to state networks maintained by public institutions or companies. There are around 3,500 data points distributed across the national territory, coming from the base generated by interpolation from 735 meteorological stations.
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, with 70% carried out in the state of Goiás (around 20 thousand ha), followed by Mato Grosso (8.5 thousand ha ), Rio Grande do Sul (1,500 ha), Minas Gerais (800 ha) and 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.
By: Eliza Maliszewski | agrolink
