The flower of the Cerrado

Farmers' growing choice for this crop is not free. After years of work, researchers from Embrapa Cerrados developed seeds that are more resistant to the dry climate and more appropriate management techniques that, combined with the market potential, contributed to awakening the interest of producers in the region in the product.

Originally from North America, sunflower is today the fourth most planted oilseed in the world, accounting for 13% of all vegetable oil produced. In Brazil, in one year, the cultivated area increased from 22 thousand to 82 thousand hectares. All this growth, however, is not enough to meet the demand of the country's oil manufacturers who, to supply the market, import the equivalent of the production of 150 thousand hectares from Argentina.

Initially, the sunflower was used by American Indians as a food source, and by Europeans and Asians as an ornamental plant and vegetable. Today it has been widely used in various forms throughout the world. Its main use is as a raw material for the production of edible oil. The bran, a by-product of oil extraction, is used by feed manufacturers for animal feed. The grains are consumed by monogastrics and ruminants, in addition to being used as bird feed. The entire plant is used in the form of silage, rolls, greens or cuts, and can offer a great contribution to minimizing problems arising from the seasonality of forage production in the Cerrado region.

The sunflower develops and produces well in temperate, tropical and subtropical climates. Its fruit, better known as seed, is called achene. Compared to most species cultivated in Brazil, such as corn and sorghum, it is a crop that has greater tolerance to drought, cold and heat. In grain producing areas, it serves as an option in crop rotation and succession systems. It demonstrates great adaptability to different soil and climate conditions, with its performance being little influenced by latitude, altitude and photoperiod.

The high quality of sunflower oil, combined with its excellent physical-chemical and nutritional characteristics, has contributed to the rapid increase in human consumption of this product. The oil extracted from the grains is rich in polyunsaturated fats (beneficial for human health) and has the best ratio of polyunsaturated/saturated fatty acids (65,3%/11,6%), which guarantees nutritional quality.

The sowing time is extremely important for the success of the crop. Initially, sunflowers were recommended in the Cerrado region to be planted in the off-season. As the region is characterized by great climate variability, it is necessary that the sowing site has sufficient precipitation for the oilseed to develop well, satisfying its requirements in the different phenological phases. The off-season is viable as long as it meets the water supply and the recommended period, which runs from the beginning of January to February 20th.

In the Federal District region, at an altitude of one thousand meters, the results of sowing carried out in November by Embrapa Cerrados demonstrated great development of sunflower with yields higher than those obtained in the off-season and the incidence of one of the main sunflower diseases, alternaria, was not accentuated. It is also possible to grow sunflowers in the off-season, with irrigation, as long as the temperature does not reach values ​​below 10ºC for long periods. The quantity of seeds used per hectare is, on average, 3,0 to 4,0 kg, depending on the size of the seed and the weight of a thousand grains (achenes).

Population density is a decisive factor for high yields and depends on the cultivar used. Embrapa Cerrados evaluated some of the main commercial cultivars and found that the population, both for silage and grain production, should be between 35.000 (only for specific cultivars) and 50.000 plants/ha. The less competition between plants, the better the spacing. But to adapt it to the production system of farmers in this region, spacing between rows of 0,70 to 0,90 m is recommended. Higher values ​​favor harvesting with the adapted corn platform.

Harvesting should be done when humidity is between 14% and 16%. There are specific cutting platforms for sunflower, but it is possible to do so with the corn platform with small adjustments. Farmers are already using this low-cost technology, developed by Embrapa Soja, which can be carried out on the farm itself. This harvester promotes a marked reduction in losses, improving harvest capacity.

The temperature considered ideal for sunflowers ranges from 27 to 28ºC. Temperatures above 35ºC reduce the oil content and, combined with low water availability, affect the plant's development. A region that has temperatures between 10ºC and 34ºC is considered tolerant to the crop.

Most of the sunflower materials grown in the Cerrado were developed in soils corrected for pH, aluminum and fertility. As sunflowers are sensitive to soil acidity, it is necessary to correct the pH and aluminum present in our soils through liming, requiring a base saturation of 50%. Chemical fertilizer must be in accordance with the recommendation established by soil analysis. In general, for Oxisols under Cerrado, 100 to 120 kg/ha of P2O5 and 40 to 55 kg/ha of K2O are used. The recommended nitrogen fertilization is 15 to 20 kg/ha of N at sowing and 65 to 70 kg/ha of N when covering between 25 and 30 days after germination.

In relation to micronutrients, boron is one of the most important elements, as in addition to sunflower being one of the most demanding crops in terms of this micronutrient, the soils under the Cerrado are largely deficient in boron. Its absence reduces production by up to 60%. It must be applied at sowing, at a dosage of 3 kg/ha of boron.

Symptoms of boron deficiency are: brittle leaves, plants with reduced capitula, plants without capitula (when this occurs, the plants present a longitudinal cut at the insertion of the capitula with the stem, causing its abscission), deformed and poorly grained capitula, and hatched seeds.

The sunflower is host to a large number of fungi, viruses and bacteria. The importance of diseases is related to varieties, cultural practices and climatic conditions (sowing times). Among them, the alternating (

) and white rot (

) are the most important.

Alternaria leaf spot attacks both stems and leaves, capitulums and achenes, causing a marked reduction in leaf area and, consequently, reducing production. It occurs under conditions of high temperatures and high relative humidity.

White rot is considered the most important disease for sunflowers in the world, infecting the roots, the collar of the plant, the stem and the head in general, remaining for many years in the soil, with its pathogenic power intact. In areas that already have the problem, since the fungus is polyphagous and is a host to beans, planting sunflowers should be avoided.

Many producers have asked whether sunflowers develop well in the Direct Planting system. What has been observed is that, even in soils with a high clay content, the Direct Planting system has proven to be highly satisfactory. The biggest problem is the efficient distribution of the seeds, as they are very light (the weight of a thousand seeds varies from 44,0g to 70,0g). Although there are already suitable discs for seeding, the fact may persist with seeding at speeds above those recommended (5 km/h).

Regarding the possibility of residues of herbicides applied to corn or soybeans harming sunflower, cases of injury have been observed in sunflower crops grown in succession to these crops, due to the short time for herbicides to degrade.

According to the literature, sunflower is sensitive to herbicides from the triazine group and imidazolinones, therefore, sowing sunflowers should be avoided in areas where imidazolinones were applied and wait 150 days where triazines were applied.

Embrapa Cerrados has been researching sunflower with the objectives of generating information on technical, scientific and economic bases, identifying possible factors that limit the establishment of this oilseed in the Cerrado and promoting its dissemination.

Embrapa Cerrados