Sunflower farming dates back to 1000BC where it was cultivated as a valuable crop. Over the centuries it has spread amongst farmers globally, especially those located in arid lands. Sunflower farming thrives under drought conditions, hence its popularity in dry areas. Sunflower has a shorter growing period of about 3 months rendering it ideal for farmers who favour crop rotation and fallow systems. It is also highly profitable because as it is used as raw material for various domestic products including cooking oil.
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Types of Sunflower
Farming sunflower usually comprises of two types, oilseed and non-oilseed. Oilseed sunflower are often black seeded and have a thin hull that adheres to the kernel. They contain 38% to 50% oil and 20% protein. Non-oilseed sunflower, also referred to as confectionary sunflower, are usually large seeded varieties that are white striped. They have a thick hull that remains loosely attached to the kernel. The oil percentage is lower and so is the test weight.
Temperature
Sunflower is highly adaptable and unlike most crops, it is more tolerant to both high and low climatic conditions. Sunflower farming thrives most in areas with temperatures ranging between 23oC to 28oC. Hot temperatures of up to 34oC have little, sometimes even no negative impact on the plant either. Temperatures above 34oC however have been reported to cause low oil percentage, reduce seed fill and negatively impact germination. Charcoal rot is also an effect of very hot weather. Sunflower farming performs well in low temperatures. Low temperatures of at least 14oC to 21oC are regarded as satisfactory for germination; though cool moist air puts the crop a risk of rust. Generally, dry climate is considered optimal for farming sunflower.
Rainfall
The amount of water required during sunflower farming depends on variety. Some cultivars are slow and therefore need an annual rainfall of 650mm to 850mm; faster growing cultivars require 500mm to 650mm. Rainfall of 300mm to 400mm during the growing season is also ideal. Excessive rainfall leads to head rot which is officially known as Sclerotinia. For this reason, ± 650 mm of rainfall is preferred. Sunflower has an extensively branched root system of up to 2m which enables the plant to survive drought periods. None the less, 20 days prior to and after flowering are most critical thus irrigation should be considered in cases of drought.
Soil Preparation
Sunflower farming thrives in a range of soil types, provided they are fertile. The ideal soils are well drained with a high water hold capacity such as loam, silty loam and silty clay loam soils, especially in drylands. Soils should have a pH level of 6 to 7.5. Lime is often used to reduce the salinity of the soil. When farming sunflower, soil preparation should be aimed at decreasing runoff so as to increase the soil’s capacity to hold water. Young sunflower seedlings are not very strong and so soils that crust easily must be worked on to ensure successful growth. Sunflower farming is highly advised on soils with witchweed as it fails to fully grow in the presence of the crop. Convectional systems are often used when growing sunflower. They involve cultivating land as a means to destroy weeds, loosen the soil surface for easy infiltration and prevent erosion. Tillage systems are also popular among sunflower farmers as they allow production of higher yields. Well prepared soils ensure the following outcome:
- good germination and an even stand
- effective weed control
- even maturity and drying
- high yields, even during drought
Planting
Sunflower farming requires a planting density of 25 000 to 35 000 plants per hectare. Row spacing should be about 30cm. Sunflower seeds must be planted in shallow depth of about 25mm in clay soils and 50mm in sandy soils. Sometimes, soils tend to compact after planting. If this happens, cultivate in order to loosen it. Areas with low rainfall require wider row spacing and less plant population. Farmers ought to be careful not to plant too little, as well as too many seeds in an area. Overpopulation of seeds results in small heads with a poor kernel development. Under population on the other hand leads to extremely large heads that cause sunflower to lodge prior to harvesting. The recommended time to plant sunflower is one week from the onset of effective rains.
Crop Rotation
Sunflower farming is regularly practised as a crop rotation measure. It is however important to note that sunflower must not be planted on the same land for more than once in 3 years. This is meant to prevent the build-up of diseases. Crops such as potatoes and groundnuts should not be rotated with sunflower as they are prone to attack by similar diseases such as Sclerotinia Wilt and Head Rot. Maize and grain sorghum are recommended. Sunflower farming is regarded as an effective rotation crop for the following reasons:
- the risk of diseases brought about by mono-cropping is reduced
- weed and pests problems are controlled by crop rotation
- allows for herbicide rotation
- increases soil fertility
- quality bumper harvest are often recorded in the follow up grain
Weed and pest control
Although sunflower farming helps to manage weeds such as the wicthweed, it is highly susceptible to weed competition during its early stages. For this reason, weeds have to be controlled, especially within the first 6 to 8 weeks after emergence. Failure to manage weeds can lead to a serious loss of yield. Weeds can be managed through the use of registered herbicides, in specified dosages. Sunflower is also susceptible to diseases usually caused by fungi. These include rust, downy mildew, Verticillium wilt, Sclerotinia stalk and head rot, Phoma black stem and leaf spot. As such, proper pesticides ought to be used.
Harvesting Sunflowers
Sunflowers are harvested as soon as the back of the heads are yellow and the outer tracts are 80% brown in order to losses caused by birds, lodging and shattering. They mature about 30 to 45 days after bloom with moisture content of 35%. Sunflowers mature before they are fully dry. For this reason, the heads must be cut and placed in thin layers on open ground to dry. Occasionally turn the heads to ensure faster and even drying. Drying sunflower takes about 5 to 8 days. Dried sunflower is then threshed and the seeds winnowed to take away any foreign matter. This is also done to avoid moulding and insect infestation. Sunflower can be stored for a prolonged period of time, up to 3 months provided their moisture is below 9%. Seeds dried at 12% moisture content can only be placed in storage temporarily. The total sunflower farming period ranges from 125 to 130 days. A productive yields is usually 1.2 to 1.8 tonnes per hectare under dry land.
Sunflower is regarded as a premium crop. It is fairly to grow, though harvesting might be a bit challenging; it matures faster than most crops. As such, sunflower farming is one of the highest financially rewarding agricultural practices. None the less, for it to be profitable, farmers need to possess proper crop management knowhow and skillset.
