The sunflower (Helianthus annuus) is a living annual plant belonging in the Asteraceae family with a large flower head.
The plant is native primarily to North and South America, and some species are cultivated as ornamentals for their spectacular size and flower heads and for their edible seed. It was introduced in Uganda in 1920’s
It is a viable commercial oil crop grown by farmers in eastern and northern part of country with potential to increase on their income.
The breeding of sunflower varieties is done by the National Semi Arid Resources Research Institute (NaSARRI) and Dr Moses Biruma the programme leader for oil crops at the Institute gives excerpts about the agronomy of the crop.
Dr Biruma explains that scientists have embarked on coming up with highbred varieties which they are encouraging farmers to grow.
Several varieties, which include Sunbeam, Mammoth, Autumn Beauty, Teddy Bear and Fedha, are grown in different parts of the country.
The total time required for development of a sunflower plant and the time between the various stages of development depends on the genetic background of the plant.
The average development of a large number of plants should be considered when determining the growth stage of a sunflower field. Maturity period iswithin 120-150 days after planting.
Sunflowers grow best on well drained, high water-holding capacity soils with a nearly neutral pH 6.5-7.5. The optimum soil classifications for sunflowers are loam, silty loam and silty clay loam soils.
Sunflower production performance on reduced agricultural capacity soils such as those affected by salinity, drought or wetness is not ideal.
Having a proper crop rotational sequence is important with all crops, including sunflowers. Extended crop rotations help reduce disease inoculum loads in the soil, allow for herbicide rotation, manage overwintering insect populations, weeds and water usage and fertility management.
General germinating sunflower seeds are very sensitive to seed-placed fertiliser. Starter applications should be placed away from the seed. When sunflowers are seeded with row equipment, all phosphate and potassium should be side banded beside and below the seed during planting.
“Fertiliser applications should be made based on a soil test. Which include sample for nitrate-nitrogen and sulphate-sulphur as well as Phosphorus and potassium,” says Dr Biruma.
Plant populations and row spacing seeding rate for sunflowers depends on type. Oil seed varieties are generally planted at higher populations than confectionary varieties. Oil-type sunflower populations range from 20,000 to 22,000 plants per acre.
Sunflowers need to be placed in moisture but not deeper than three inches about 7.6 cm. The ideal seeding 3.8 to 5 cm deep. Planting equipment should firm the soil over the seed row to maintain a moist seed bed and ensure good seed to soil contact.
The plant is a host to a number of pests. Which means fields should be monitored regularly for potential problems, to determine pest species present and if populations are at economic threshold levels.
Field scouting involves walking into the field and assessing the overall health of the crop. Sunflower pests tend not to be distributed evenly throughout a field, so fields should be checked in several locations.
Many tillage regimes are practiced by farmers including conventional, strip, ridge, minimum and zero-tillage.
Many factors are to be considered when deciding what tillage regime to utilize, including soil type, climate, fertiliser and rotation. Different tillage regimes are associated with different impacts on crop production and the environment. For example, conventional tillage can be utilized to control specific crop pests, however it is also associated with erosion.
Weeds compete with sunflowers for resources, limiting crop growth and reducing yield. Yield losses caused by weed competition is a factor of weed species, density, relative time of emergence to the crop and environmental conditions. Weed species differ in competitive ability; some causing higher yield losses on a per plant basis.
Sunflowers are a good competitor once the crop is established. Weed competition during the early stages of growth has the largest impact on yield. Farmers may start weeding two weeks from date of germination and do so after two months depending on the magnitude.
“Start harvesting as soon as 80 per cent of the sunflower heads are ripe in order to minimize loss from birds and from shattering,” says Jane Akello an agronomist as NaSARRI.
Harvesting is done by cutting off the head when it is not completely dry, they are stored under the shed on polythene mat and the seed is processed by threshing using sticks.
The seed is then dried under hot sunshine for a period of one week. The harvested sunflower should not be left to dry completely because it becomes a challenge to separate the seeds
Store dried seed in a pics bag consisting of two layers of polyethylene liners which will keep it safe over a long period of time.