OVERALL OBJECTIVE
Assessing the production levels of sunflower in Botswana
SPECIFIC OBJECTIVES
- To assess the production level of sunflowers in farming of Botswana.
- To compare the production levels of traditional and commercial farming systems of Botswana.
INTRODUCTION
Sunflower (Helianthus annus L.) is the most important oil seed crop in Southern Africa at present and is being grown virtually in all summer rainfall areas. Marginal soils are being utilised more for production of sunflower which is less risky and require lower production inputs. It is expected that the demand for vegetable oils and proteins will increase in future, and sunflower is the ideal crop for oil production. Since the advent of hybrid sunflower, the traditional problems such as uneven height and maturity have been largely eliminated as a result it sis now easier to handle and has become an excellent crop to maize and sorghum. Sunflower requires low humidity and sunny conditions for optimal plant growth and development making it suitable for production in Botswana.
WHY GROW SUNFLOWER
- Shorter growing season and better cold tolerance makes it suitable for later planting
- Ideal for crop rotation and cultivated under varying climatic conditions
- Have deep taproots and can obtain nutrients from deeper parts of the soil profile 1.5 to 1.8 which are unavailable for most annual crops making sunflower a hood rotational crop
- Performs well under drought conditions since its roots can extract water from deeper parts of the soil profile where other crops’ roots cannot reach
- Sunflower seeds are more tolerant to frost thus making sunflower an attractive crop where frost may occur during seedling stage.
- Sunflower responds to fertilisers but requires less fertilisers than most crops
- Economically viable crop alternative
- It is well adapted agronomic ally to both irrigated production and dry land cropping systems
- Higher yielding cultivars exhibit the highest water use efficiency
CLIMATIC AND SOIL CONDITIONS
Sunflower requires low humidity and sunny conditions for optimal growth and development with optimum temperatures 23˚C - 27˚C. Temperature for germination should not be below 4˚C - 6˚C and seedlings may withstand short periods of frost down to ˗˗5˚C (Van der Vossen and Fagbayide 2007). In Botswana a well distributed annual rainfall of between 500 and 600mm is ideal and deep soils with high water holding capacity allow sunflower to fully utilise its extensive root system for exploitation of moisture and nutrients. Sunflower also grows best on soils with good drainage and pH range of 6.5 to 8.5 (Tsuaneng and Maphanyane 2000).
LAND PREPARATION
The seedbed should be prepared so that it is moist and firm with the surface rough enough to minimise soil drifting (Grady 1999). Deep winter ploughing improves soil moisture infiltration and storage. Secondary cultivation may be required to kill weeds and prepare a fine seedbed (Tsuaneng and Maphanyane 2000). Soil structure breakdown or compaction caused by excessive land preparation should be avoided because it promotes reduced aeration and water movement and increases the probability of Downy mildew in areas where the disease is prevalent (Schneifer and Miller) 1995).
FERTILISER REQUIREMENTS
In general sunflower does not respond to high N input but a basal application of 40 kg/ha of N is recommended. The recommended Potassium and Phosphorous rates are 50kg/ha and 20 – 30 kg respectively. Boron is important and should be applied on the basis of soil test results (Tsuaneng and Maphanyane 2000) but an application of 1 – 4kg/ha is normally adequate. Recommended applications of fertilizer to sunflower crops with expected seed yields of 1.5 – 2.5 t/ha vary 50 – 120 kg N, 20 – 30 kg P and 40 – 80 kg K. Seed oil content tends to decline and protein content to increase with higher Nitrogenous fertiliser application (Van der Vossen and Fagbayide 2007).
PLANTING AND PLANT POPULATIONP
Planting in Botswana should be done in early December except in North Eastern Botswana where planting after mid January is advisable. The seeding rate is 5kg/ha but it may change depending on cultivar and the planting depth is 4 – centimetres. Between row spacing of 0.75m is recommended except for Pandamatenga where row spacing of 1m is usually used. Within row spacing should be adjusted according to interow spacing to achieve a plant population of 30 000 to 35 000 plants per ha (Tsuaneng and Maphanyane 2000). However optimum final densities vary with environmental and cultivar with 15 000 – 30 000 plants/ha for rainfed and 40 000 – 60 000 plants/ha for irrigated sunflowers. Sunflower has some ability compensate for low densities or irregular crop stands by increasing total biomass, seed size and number of seeds per plant provided other growth factors such as moisture and nutrients are not limiting. Intercropped with groundnuts, pulses and millets. Higher plant populations are planted for oil types than for confection hybrids (Van de vossen and Fagbayide 2007).
TYPES OF SUNFLOWER
There are two types of sunflower. There are oil seed hybrids which are used for oil production and are either linoleic or oleic types. These hybrids are generally black seeded and have a thin hull and adheres to the kernel. They have about 38-50% oil and 20% protein. The non oil seed hybrids are referred to as confectionery and they are striped or large seeded varieties with a thick hull which remains loosely attached to the kernel permitting more complete dehulling. They also have lower oil percentage and test weight (Schneifer and Miller 1995).
CULTIVARS
Recommended cultivar for Botswana is Russian number 4 that matures in 140-150days and grows to a height of 150-165cm. Its seed size is 1-1.5cm long and 0.5-0.8cm wide. Its colour is black, with black grey stripes. The yield potential is 8t/ha (Tsuaneng and Maphanyane 2000).
MANAGEMENT PRACTICES
Sunflowers are very susceptible to seed placed fertiliser injury. To avoid seedling injury, place fertiliser in a band 5cm below or beside the seeds. Sunflowers are usually planted at low densities and grow slowly during the first 2 weeks. Weeds that emerge and establish during this time can be competitive and reduce sunflower yield (Hurt 2008). Weeds should be controlled by hand hoeing, inter-row cultivation or herbicides. Herbicides recommended for use on sunflower in Botswana are dinitramine (cobex), trifluran (treflan), pendimenthalin (stomp), alachlor (lasso) and metalachlor (dual ) (Tsuaneng and Maphanyane 2000). Good weed control conserves soil moisture and management practices which promote infiltration of water in the soil and limit evaporation from soil generally will benefit sunflower in terms of available moisture. Sunflower yield is most sensitive to moisture stress during the flowering period and least sensitive during the vegetative period and so farmers are edged to irrigate at flowering if there are less rains (Grady 1999). For bird control avoid planting sunflower within a quarter mile of marshes, dams and rivers as they harbour large quantities of birds and contain water late in summer. Farmers should also leave at least a 100 yard buffer strip of a crop not as attractive to birds adjacent to shelter belts, groves or other wooded areas. Mechanical frightening or chemical agents can also be used to control birds.
YIELD
The yield potential of sunflower is 8t/ha in Botswana (Tsuaneng and Maphanyane 2000) and world average yield is 1,2t/ha and national averages in Africa range between 0,4-1,3t/ha ( Van de Vossen and Fagbayide 2007).
PESTS AND DISEASES
The African bollworm is an occasional problem in sunflowers while doves are a persistent problem (Tsuaneng and Maphanyane 2000).Other pests include cutworms, mole crickets, grasshoppers, leafminers, aphids and diseases include rust, alternaria blight, septoria leaf spot and viral diseases include sunflower mosaic virus (SuMv) and tobacco leaf curl virus (TLCV) and attacked by nematodes meloidogyne and rotylenchus species (Van de Vossen and Fagbayide 2007).
HARVESTING AND STORAGE
Sunflowers are harvested when heads have turned yellow-brown and seed moisture content is 10-12 %. Harvesting is done by hand or machine and a combine harvester should be used when the crop is completely dry (Tsuaneng and Maphanyane 2000). Chemical desiccants can be used to dry sunflower for machine harvesting. Sunflower should be stored indoors in bags in an elevated platform. A crop produced for oil processing should be sent to the market as soon as possible to avoid deterioration in oil content and quality (Hurt 2008).
USES
- Produce oil which is used as cooking and salad oil in the manufacture of margarine, paints, varnishes and soap.
- Sunflower meal is rich in protein and is used as livestock feed. Defatted sunflower meal is also suitable for human consumption as a substitute for wheat flour in baking bread and cakes.
- Stalk and flower heads are processed into cellulose and fibre mats.
- Seeds from non-oil cultivars are consumed directly, roasted and salted and some as hulled kernels in various confectionery and bakery products and the smallest seed as bird seed and pet food.
- Sunflower is also grown as a forage crop, as an ornamental or as a pot plant and is an important bee plant (Van de Vossen and Fagbayide 2007)
Sunflower yield in kg/ha per region
| Region | Year | |||||||||
| | 1989 | 1990 | 1993 | 1995 | 1996 | 1997 | 1998 | 1999 | 2001 | 2002 |
| Southern | 200 | 200 | 69 | 192 | 32 | 146 | 40 | 38 | 183 | 86 |
| Gaborone | 100 | 200 | - | - | - | 176 | 48 | 130 | 69 | - |
| Central | - | - | 9 | 217 | 429 | 125 | - | 100 | 184 | 92 |
| Francistown | - | - | 8 | - | 623 | - | - | 194 | - | - |
| Maun | - | - | - | - | - | - | - | - | - | - |
| Western | - | - | - | - | - | - | - | - | - | - |
| Traditional | 64 | 100 | 50 | 185 | 65 | 147 | 32 | 69 | 156 | 85 |
| Commercial | 400 | 500 | 453 | 354 | 310 | 831 | 504 | 454 | - | 690 |
| Total | 200 | 300 | 120 | 204 | 88 | 346 | 466 | 431 | 156 | 663 |
DISCUSSION
The average sunflower yield (kg/ha) was almost constant from 1989 to 1995 mostly in the Southern region but was very low with less than 200kg/ha.This maybe of poor rainfall conditions which prevail in Botswana. There was however a sharp increase in yield in 1996 in the Francistown and Central regions with a maximum of above 600kg/ha in Francistown. From 1997 onwards the yield for all regions was very low with averages being below 200kg/ha.
The average total yield from 1989 to 1996 was fluctuating between 88 and 300kg/ha. It rose steadily to above 400kg/ha in 1998 and99 and declined in 2001, only to rise again to reach a maximum of above 600kg in 2002. There was however a steady increase in yield in the commercial system from 1989 to 90 followed by a steady decline in the subsequent 3 years. The yield then increased sharply to reach a maximum of above 800kg/ha in 1997 then declining to below 500kg/ha, and then increasing again in 2002 to above 600kg/ha. The traditional yields were fluctuating over the period from1989 to 2001 between 50 and 200kg/ha and the reasons for the fluctuations may be due to different seasonal rainfall patterns.
Description of trends is difficult particularly because its hampered by unavailability of data from some regions.
CONCLUSION
Yields of oil crops are consistently low in all farming regions as they are below the expected Botswana yields and this is probably due to poor rains and substandard management. The subsistence farmers are getting lesser yields as compared to the commercial farmers and most of these small scale farmers who are growing oil seed crops have limited access to resources and markets. Most of them cannot at present afford expensive capital developments or purchased inputs. The physical, financial, technical, commercial and administrative support which farmers in the industrialised countries are getting is not mostly available to them. However significant improvements are already technically possible as new cultivars with durable and stable resistances, tolerances and adaptations to biological and environmental constraints have been and are being developed. Establishment of local industries that use oil crops as raw materials can also help to provide market for the oil crops produce and thus gives farmers an incentive for spending more on inputs and thus produce more.
RECOMMENDATIONS
The market demand should be sustained so that an efficient and reliable seed industry can deliver improved seeds to farmers. Farmers should also purchase seed from reputable seed companies or dealers with a good technical service record if production problems do occur and assistance or consultation is required. The cultivars which the seed companies must offer should provide a measure of insurance against pests, diseases and drought and this would encourage both small scale farmers and large scale farmers who are entering agriculture to use more productive methods including timely sowing and control of weeds to ensure higher productivity. Farmers should also use several criteria in sunflower hybrid selection and so they should also look at seed potential yield, stalk quality or reaction to damage from pests, high winds, uniform stalk height at maturity, oil percentage (genetic potential), physiological maturity ratings, test weight and self compatibility (ability of sunflower to pollinate itself in the absence of insects) and also select varietal plant types with head types that face down after flowering to minimise bird damage. The farmers should always seek for assistance from the nearest offices of the Department of Agriculture
REFERENCES
Grady K. 1999. Sunflower production. South Dakota State University.
Hurt E.F. 2008. Sunflower for food, fodder and fertility.
Schneifer A.A and Miller J.F. 1995. Sunflower production. Northern Dakota State University.
Summerfield R.J and Roberts E.H. 1985. Grain legume crops. Cpllins Professional and Technical Press.
Tsuaneng M.M and Maphanyane G.S. 2000. Field crops reference Handbook in Botswana Department of Agriculture Research.
Van de Vossen H.A.M and Fagbayide J.A. 2007. Helianthussannus L. Plant Resources of Tropical Africa. http://database.protabase.org. Accessed 17th April 2009.
10. Wynne J.C and Rowe R.C. 1998. Advances in Agronomy.
