Everything you need to learn about growing oilseed crops in Australia. Learn about:- 1. Safflower 2. Sunflower 3. Soybean 4. Linseed 5. Rapeseed.
The growing of the oilseed crops has increased very greatly in recent years and sunflower is now Australia’s seventh biggest crop in the area grown.
Oil is produced from two kinds of oilseed crops:
1. Those like sunflower, soybean, rapeseed, linseed and safflower which are specially grown for oil.
2. Those like cotton, peanuts and maize which are grown mainly for other purposes.
Much vegetable oil is now used to make margarine which contains more of the special oils called “unsaturated fats” which are less likely to cause heart disease than the saturated fats of animal origin. It can be seen that safflower and sunflower are specially desired for making margarine but the first of these crops is very difficult to grow properly.
How to Grow Safflower?
Safflower, Carthamus tinctorius, is an erect annual which produces oil of high quality. Although the plant grows well on the Darling Downs and parts of the north west of New South Wales, yields of safflower have been variable and sometimes disappointing. Safflower is not yet a safe crop and much needs to be learned about how to grow it in Australia.
Botany:
When the plant first begins to grow, it forms a flat rosette of leaves. Later the stem elongates and branches, each branch ending in a flower head. The flower heads consist of 20-170 florets surrounded by green bracts.
In each floret the stigma is enclosed by five anthers joined into a tube shape. When the florets open, the stigma grows up through the anther tube carrying the pollen with it. The florets may be self-fertilised or cross-fertilised with pollen brought from other florets by bees.
Climate:
Although the seed will germinate at temperatures down to 4°C, the best temperatures for germination and growth are 19° – 24°C. When the plant is in the rosette stage it is fairly resistant to frost, but is susceptible to weed competition. High temperatures at flowering may affect yields of seed and oil quality.
Diseases:
Safflower is affected by rusts, root rots; blight and leaf spots, but insect, attacks are usually not a great problem.
Management:
Safflower can be seeded at a depth of 5 cm at the end of winter in wheat areas. It prefers soils of high fertility, good drainage and neutral reaction. It is recommended that, in dry-land cultivation, safflower be seeded at 9 to 16 kg/ha with 36 cm row spacing.
With irrigation the rate should be 22 to 28 kg/ha with row spacings from 50 to 90 cm. Gila is a popular variety. The flowers are easily damaged by rain, and since flowering lasts for four weeks, yields are often reduced by rain which falls at this time. The crop is usually harvested with a header.
How to Grow Sunflower?
The sunflower (Helianthus annuus) originally came from Mexico, but it is in the USSR and the Eastern European nations that it has been cultivated extensively.
The increase in sunflower production in Australia was partly due to the controls placed on wheat production, and it reached a peak in 1972. Since then the area grown has declined, but it is still very important in the north-western wheat areas of NSW, in the southern part of the Northern Tablelands, in the Inverell area and the Murrumbidgee Irrigation area.
It is also grown on the Darling Downs and Central Highland areas of Queensland. It has also been tried in Victoria and Tasmania.
Botany:
The sunflower has a single stem which may vary in height up to five metres, but most modern varieties vary from 1.2 to 2.4 metres. The large leaves are palm-shaped and alternately arranged but the first few leaves may be in opposite pairs. The large flat flower heads vary from 76 to 500 mm in diameter.
Three rows of green bracts cover the under-side of the flower heads. The upper side of the head is surrounded by a single row of infertile ray florets with bright yellow petals united into a single strap-like ray.
The disc of the flower head is covered by hundreds of small disc florets, each one of which possesses a small tubular petal tube or corolla. The five small stamens in each flower are joined to form a tube. When flowering begins, each floret on the outside of the disc opens first.
The filaments of the stamens lengthen and this makes the stamen tubes protrude from the corolla. Pollen is released into the hollow stamen tube. Then the stigma grows up and pushes the pollen out of the floret.
The disc florets cannot be self-fertilised so pollen from other flowers is carried by bees and other insects. After fertilisation the grain grows rapidly in each floret, most of the food being made by the topmost leaves near the flower head. There are usually 1200-1600 seeds per head.
Climate:
Young sunflowers and those with developing grains are able to withstand light frosts, but frosts may kill plants in between these stages. Sunflower plants are very susceptible to drought up to five weeks of age but are more resistant later.
Cool temperatures during growth favour the production of a high oil content, but high temperatures cause a lower percentage of unsaturated oils to form.
Genetics:
Much progress has been made through the breeding of new varieties such as Hysun and Suncross and the use of imported varieties, especially some from Russia. In addition some hybrid varieties have been bred, some branched varieties and some which have resistance to rust diseases.
Sunflower may be attacked by red rust, white blister rust, leaf spots, stem and root rots and head rots. The best defence against rust seems to be in finding resistant varieties.
Cutworms, Rutherglen bugs and green vegetable bugs may damage the plants, but insecticides can be used. The danger however is that these chemicals may kill bees needed for pollination of florets.
Sunflowers grow well in soils of medium to high fertility with good drainage. They respond well to high phosphorus in the soil and also nitrogen. Sometimes trace element fertilisers for zinc and molybdenum need to be added.
In the North West area of New South Wales crops sown in early September give the highest grain yields. They may escape most of the rust damage. The seed must be sown into a good seed bed with a wheat combine with 36 cm row spacings. If the crop must depend on rain only a population of 11 000 plants per hectare is best, but if irrigation is used the population may go up to 16 200 plants per hectare.
Seeds are sown at a depth of 2.5 to 7.0 cm, the best depth being 2.5 to 3.5 cm. A germination percentage of 80 per cent can be expected. The use of culti-packer rollers after sowing is recommended to bring moisture up to the seeds.
Weeds can be a bad problem in sunflowers and the use of the pre- emergence chemical Trifluralin is recommended.
Harvesting can begin when the backs of the seed heads turn yellow to black and the base is dry. The seed can be harvested at 18 per cent moisture if it is to be dried later, otherwise it should be less than 10 per cent in moisture content. Sunflower yields can rise to more than 2300 kg per hectare.
How to Grow Soybean?
The soybean (Glycine max) is now the world’s largest source of vegetable seed oil. The seed meal after crushing is also an important protein stock food. Soybeans are the largest area crop in the USA. There is a big opportunity for the growing of this crop to be developed in Australia, because of its local usefulness and the high cost of importing soybean products.
Much progress will be made in breeding varieties like Bragg and Ruse better suited to Australian climates and in developing better ways of growing the crop. We also need to choose more carefully the parts of Australia where the crop can best be grown.
The soybean is an erect bushy annual varying between 20 and 180 cm in height with alternate leaves with long slender petioles. Most parts of the plant are slightly hairy. Axillary buds may give rise to leafy branches or to flowers.
The flowers are small, purple or white in colour and carried in clusters of 3-15. Many of the flowers drop off without forming pods. Most of the pods formed contain 2 to 3 seeds.
The plant forms a taproot but from the top 10-15 cm four rows of secondary lateral roots are formed at 90° intervals. These laterals grow horizontally for 40 or 50 days and then turn down.
The soybean is very sensitive to day length, more so than any other crop. Different varieties have different needs, but most are short day plants.
The ideal summer temperature is between 27 and 32°C. They need 4 to 5 months of frost free conditions. Soybeans are very susceptible to drought stress at the time of flowering.
Provided the right bacteria are present in the soil, soybeans begin to fix nitrogen 20 days after germination. Fertiliser nitrogen is of benefit in this early period. Since Australian soils do not normally contain the rhizobia for soybeans, inoculum is usually applied as wet slurry to the seeds.
Diseases do not appear to be a serious problem with soybeans. Asian rust is the worst danger.
The pre-emergent weedicide Treflan is usually used, but only with irrigated crops.
Most varieties are best planted in November or December, for the wet season begins then in the north. A dry autumn gives good conditions for ripening the seed and harvesting. For irrigated crops the aim should be populations of 40 to 60 000 plants per hectare.
79 per cent of the Australian crop is irrigated (96 per cent in New South Wales). Commonest row widths are 64 to 100 cm but rows can be planted much closer than this in some cases.
There are two serious problems in growing soybeans:
1. The abortion of flowers, pods or seeds. Usually there are 3 or 4 times as many flowers formed as pods. A dry period may cause empty pods through seed abortion.
2. The shattering of the pods before harvest will scatter the seed on the ground. It is therefore advisable to harvest at a moisture percentage of 12 to 13 per cent but no later.
Average yields of soybeans are about 1880 kg per hectare, but a record yield of 4700 kg per hectare has been obtained.
How to Grow Linseed?
Linseed, or Linum usisatissimum, is closely related to the flax plant. It is a small plant with stiff upright stems, and is grown for its seed. Linseed oil is used in the paint industry, and the seed is used to make protein concentrates, such as linseed cake.
Linseed may be grown in the more favoured wheat areas wherever spring frosts are not severe. Rain is needed after sowing and at flowering time. Drought and high temperatures above 32°C at or near flowering reduce yields and the quantity and quality of oil. Linseed may be killed or damaged by temperatures below –4°C when young, or below –1°C at flowering, but between these stages it will stand temperatures of –9°C or less.
The seed is drilled in with a combine in autumn at a depth of two and a half or four cm. The seed should be sown through all tines of the drill, using the fine side of the seed plates in the up position. Seed is sown at rates varying between 31 and 45 kg to the hectare. Early sowing is favoured in some areas to enable the plants to escape insect attack.
The great problem in linseed growing is attack by the corn or ear worm, Heliothis armigera. The caterpillar of this insect attacks the plant after flowering and eats the entire contents of the fruit. The only way to control this pest is to spray with Maldison.
In the 1978-79 season, aerial spraying cost $5 per hectare and boom spraying from a truck $2.70 per hectare plus the cost of chemicals. It may be necessary to spray a crop several times.
In good wheat areas yields of linseed average about 1000 kg per hectare, but high prices may be obtained. In recent years, the price of bagged linseed has reached $250 per tonne.
How to Grow Rapeseed?
Some varieties of rape have been used as forage plants for many years, but these are not suitable for oil production. Two species of rape are grown for oil—Brassica napus and Brassica campestris, and there are many varieties of each species.
The most favoured varieties are those like Oro, Zephyr and Polar Span which has low amounts of a substance called erucic acid which is thought to have unhealthy effects on humans.
Plantings of rapeseed in New South Wales increased from a small area in 1969 to an area of 77 142 in the 1972-73 season. They fell to a low area of 8509 hectares in 1976-77 but rose again to 14 725 hectares in 1977-78.
In 1979 the price received by the grower was $2.80 per kg or $95 per 50 kg sack. Rapeseed may be grown in the wheat belt and in crop areas of the tablelands. It has done best in the southern parts of New South Wales.
In the wheat areas varieties of B. napus are sown at the same time as mid-season wheats but they can be sown in late winter or early spring on the tablelands. Varieties of B. campestris are sown later in both areas. Rape can survive light frosts, but frosts will kill flowers.
Rape is sown in rows 18 cm apart at a rate of 4.5 to 6.5 kg per hectare for B. napus and 3.5 to 4.5 kg per hectare for B. campestris which has smaller seeds. With irrigation, higher seeding rates can be used. The seed is sown 2.5 to 3.8 cm deep into moist soil, and can be drilled in by mixing seed and fertiliser in the fertiliser box.
Fertilisers as for use with wheat are recommended. Young rape plants suffer heavily from competition with weeds. Blackleg is a fungus disease which lives on in crop residues, so rape should not be sown in the same paddock for five years if the disease occurs.
Insect pests such as aphids, red-legged earth mite and blue oat mite may be controlled by using metasystox or Rogor.
Rape is ready for harvesting when the stem and pods turn a straw colour and the seeds rattle in the pods. It must be harvested as soon as it is ripe because seed will be lost if pods shatter. Using a header early in the morning or late afternoon and moving it at slow speeds will reduce losses of the small seeds through shattering.