Everything you need to learn about growing and harvesting wheat in Australia:- 1. Introduction to Wheat 2. Botany of Wheat 3. Soil 4. Climate 5. Harvesting 6. Varieties 7. Diseases 8. Management.
Introduction to Wheat:
Wheat, or Triticum vulgare, is one of the world’s most important grain crops, because it can be grown in a wide variety of soils and climates, and because it is a valuable food. Of all the cereal grains, only wheat and rye can be made into bread.
Wheat is the most important single crop in Australia. The total area of land sown to wheat in Australia in 1978-79 was over 10 million hectares. About 46 700 farmers grow the Australian wheat crop and the average area sown is about 113 hectares.
Australia today ranks as the fifth biggest wheat-producing country and the third biggest exporter of wheat grain in the world. Although Australia has greatly increased its exports of minerals and manufactured goods, 47 per cent of our export income still comes from selling agricultural products. Although the value of our wheat exports varies a good deal, these exports usually average about 15 per cent of the total value of agricultural exports.
In 1976-77 The People’s Republic of China bought 745 000 tonnes of our wheat which was one third of the whole crop. This wheat was worth $74.1 million to Australia, and China was one of our best customers.
Wheat was first grown in Australia on land which is now part of the Botanic Gardens in Sydney. Later it was grown near Parramatta by James Ruse and others. Tasmania then became the main wheat-growing state.
Between 1850 and 1890, land was opened up for settlement in South Australia, and this state then took the lead in wheat production. Extensive wheat growing in Victoria and New South Wales began after the gold discoveries and the opening up of new farm lands as a result of the Selection Acts.
Australian wheat growing has been changing in recent years. For instance there have been changes in the importance of various wheat- growing districts. Less wheat is now grown in the Riverina, mainly because of the spread of skeleton weed.
At the same time, the northwestern wheat districts have become the chief centre of wheat production in New South Wales. Wheat growing is becoming more important in Queensland and in Western Australia.
Another change is that the kinds of wheats being grown are now different. Many modern wheat varieties are quite short when compared with older varieties and are less likely to be blown over or “lodged” by storms. Moreover more wheat is now being grown which produces flour of good baking quality.
The most important change in the wheat industry has been the fairly rapid rise in yield. From an average of 0.8 tonnes per hectare in 1931-35, average yield rose to 1.3 tonnes per hectare for the season 1976-77. Moreover it is expected that within the next ten years the Australian average yield will have risen to about 1.7 tonnes per hectare.
Although wheat breeders continue to breed new wheat varieties with higher capacity to yield, the main reason for this rise in yield is that more and more wheat is being grown on pasture leys. The pasture legumes have added nitrogen to the soil, and this nitrogen has stimulated grain production in wheat.
It is certain that new varieties of wheat with much higher ability to yield will be bred in the future, so the yield per hectare can be expected to rise still further. Perhaps the high yielding qualities of the Mexican semi dwarf wheats will be used to breed new higher-yielding Australian varieties, although results so far are disappointing.
Botany of Wheat:
Wheat is an annual grass. The grain is oval in shape, and has a round side and a grooved side. The wheat embryo, or “germ”, is found at one end on the round side. The opposite end bears some fine hairs, and is called the brush end.
The wheat embryo is a miniature plant with a minute root, or radicle, and a small shoot, or plumule. In the centre of the plumule is a minute dome of cells called the shoot apex. This is a most important part of the embryo, for when the grain germinates, the shoot apex makes the leaves, the stem and finally the ear or head. By the time the grain is mature, the shoot apex has already formed two or three miniature leaves.
These embryo leaves are covered by a sheath called the coleoptyl. The embryo is attached to the food supply by a pad of cells called the scutellum. Between the scutellum and the endosperm is a sheet of cells containing the starch-dissolving enzyme diastase. When the grain is planted in moist soil, the enzyme diastase spreads into the endosperm and turns the starch there into sugars.
The sugar solution then passes outwards to the embryo. The embryo cells use the sugar as energy food until the first leaves appear above the ground and begin to make food by photosynthesis.
When a wheat grain is sown in moist soil, the plant passes through the following stages of growth and development:
1. The grain absorbs water and swells. The embryo begins to grow, and appears as a prominent bump at the bottom of the grain. The wheat at this stage is described as sprung grain.
2. The first seminal root breaks out of the grain, which is then said to be shot grain.
3. Two other seminal roots appear. All seminal roots produce a coating of root hairs which enable them to absorb water and nutrients from the soil.
4. The plumule emerges from the grain and grows towards the soil surface.
5. The white coleoptyl appears above the ground. The grain has germinated, but is growing slowly.
6. The node to which the first leaf is attached has by this time been carried upwards to a position about 25 mm below the soil surface. The first leaf is at first enclosed in the leaf sheath or coleoptyl, but it grows rapidly and breaks through the coleoptyl at the surface.
7. The second leaf then emerges from the sheath of the first leaf. Wheat seedlings at the two-leaf stage are not strong and are easily affected by adverse conditions.
8. Other leaves emerge and begin to make food in the sunlight. At this stage the stem is still under the surface of the soil and is very short.
9. Buds which lie between the stem and each of the first three leaves then begin to grow into stems with leaves attached to them. In other words, branching or tillering takes place. Later, secondary tillers may form at the base of leaves on the first or primary tillers.
The more tillers that are formed, the heavier the crop will be, but the number of tillers depends on the supply of water and soil nutrients, the variety sown and the density of planting of the crop. The new variety shorten tillers very well.
10. Provided that the soil is moist at a depth of 25 mm below the surface, the crown or secondary roots are formed while tillering is taking place. These roots arise from the first node and from other nodes near it. Unless crown roots are formed, the plants will not develop properly, and the crop will be light.
11. About six weeks after tillering begins, the shoot apex of each stem has formed all the leaves that will be made. The apex then makes a minute seed head, or inflorescence. The number of flower buds formed at this time is determined by the fertility of the soil, so that the size of the crop is determined very early in the growth of the plant.
Having made the immature ear, or head, the shoot apex ceases its growth. Its position is still very close to the ground surface. At this stage a wheat crop which is too leafy may be safely fed off with sheep, for the small ears are too close to the ground to be eaten.
12. At the end of winter, the stem internodes begin to lengthen inside the leaf sheaths. At this time the crop begins to grow taller, and this is called the spindling stage. It is then too late to graze the crop.
13. Usually by mid-September the small ears of wheat begin to move up through the leaf sheaths. Rain is needed at this time to ensure a good set of grain. Eventually the ears enlarge and swell out the topmost leaf sheath. This is called the boot stage.
14. The ears, or heads, then emerge from the top leaf sheath. This is called heading out.
15. The wheat then flowers, and the young grain is formed. At the time of flowering when the delicate sex organs of the flowers are exposed to the air, the wheat plant is again at a stage when it may be harmed by unfavourable conditions such as frost, hot dry winds or chemical sprays.
16. After flowering, some of the food stored in the stems and leaves is transferred to the grains forming in the heads. The stems and leaves have then turned into straw which has low food value.
17. Finally the plant dies, and the grain in the heads turns brown and is ready for harvesting. Rain at this time can cause the wheat to become sprung or shot in the heads, rendering it of less value as seed.
The whole wheat head is called a spike, and the flowers are carried in bunches called spikelets. Each fertile wheat floret consists of a green ovary with a two-branched feathery stigma, and three stamens. These structures lie in a hollow leaf-like lemma, the open side of which is closed by a papery palea.
When the floret blooms, two minute green lodicules at the base of the ovary swell up. This causes the palea to move away from the lemma. The stamens shed their pollen, which then falls on the stigma.
Soil Required for Growing Wheat:
Wheat soils in New South Wales are of three chief types. The red-brown earths occur widely in the Riverina, central western slopes, the upper Hunter Valley and parts of the Tamworth and Gunnedah district. Many of these soils contain a good deal of silt, and easily form clods which have to be worked down to a suitable seed bed.
These are not extremely fertile soils, so the crops they produce are of moderate yield. Wherever yellow and white box trees grow on these soils the country is said to be suitable for wheat.
Large areas of lighter sandy loams occur in parts of the Riverina, and the Premer, Mullaley and Pilliga districts. These soils are generally poor in soil nutrients, but crops grown in them suffer less in dry periods.
Much wheat is now grown in the heavy black soils of the Liverpool Plains, Breeza Plains, and in the plains country west of Inverell. Similar soils occur in the wheat belt of the Darling Downs. These are self- mulching soils and dry out quickly at the surface. Therefore a culti-packer should be used after sowing to consolidate the surface and bring moisture to the germinating grain.
Climate Required for Growing Wheat:
There is an old English saying that “frosted wheat means empty heads”. Wheat was once grown extensively on the tablelands of Victoria and New South Wales, but it was found that spring frosts often killed the young flowers. The only way to be sure of a crop on the tablelands is to sow the wheat at the end of winter as is done in Canada.
Rainfall is the chief factor which limits wheat growing in Australia. Most wheat is grown in areas receiving between 380 and 630 mm of rain. It is an unreliable crop in districts where the rainfall is less than 380 mm. However the time when the rain falls is more important than the total amount of rainfall.
Rain is needed in May to germinate the grain, and in September when the crop is beginning to head out. The summer rainfall areas of the north-west are more suitable for wheat growing, because rain falls at the time when the evaporating power of the air is increasing.
Harvesting of Wheat:
Hay Harvest:
The crop is cut when the bases of the stalks are yellow. The grain is turning into soft dough at this time. The reaper and binder cuts the crop and binds it into sheaves, which are arranged in the form of stooks to dry out. Wheat hay may be baled, but must be properly dry before this is attempted. Yields of hay vary from 1.8 to 4 tonnes per hectare.
Grain Harvest:
The grain must be hard before harvesting is commenced. The time of harvesting varies with the district. There is a sudden summer in Queensland and the north-west of New South Wales, and the first harvests usually occur in late October. Most Australian wheat is harvested in November, but in cold districts the harvest is usually much later.
Crops are harvested with a header, which cuts off the heads, thrashes out the grain, and separates the grain from the chaff and straw.
The development of the grain auger has allowed bulk handling techniques to be used in the wheat harvest.
The average yield for the years 1976-77 was 1.4 tonnes per ha for Australia as a whole. Capable farmers on good land have obtained yields of up to 4.7 tonnes per ha but when irrigation is used with fertiliser nitrogen, yields up to 5.5 tonnes per ha have been obtained.
It has been estimated that insect spoilage costs the Australian wheat industry about $25 million each year. Bulk handling of grain by the state authorities is strictly controlled, but there is no control over what the farmer does with his machinery.
The main trouble comes because farmers do not clean their harvesters and storage facilities. Weevils breed in grain which is left after harvest. It is most important that all grain is removed from headers and all harvesting equipment sprayed with insecticide. Storage bins may be fumigated.
Wheat grain is sold through the Australian Wheat Board. All grain which the farmer decides to sell goes to government silos. From here it goes to the wheat pool. The grower is paid so much a tonne for ASW or Australian Standard White, wheat. To reach this standard, wheat must weigh a certain amount per hectolitre, and must not contain more than 5 per cent of cracked grain and screenings. The ASW standard is fixed each year.
Varieties of Wheat:
One avenue of improvement in wheat growing is to make use of the best varieties available for a district.
Wheat varieties differ in botanical characteristics, such as:
1. Size, colour and hardness of grain.
2. Length of stalk.
3. Strength of stalk.
4. Length and width of flag.
5. Presence of awns on the head.
6. Shape of head.
Varieties also differ in other ways, such as:
1. Drought resistance.
2. Maturity.
3. Baking quality of the flour.
4. Resistance to such diseases as stem rust, flag smut, bunt and leaf rust.
The ideal wheat variety would be one which combined resistance to all the common diseases, high yield, strong flour, drought resistance and strong straw. None of the present varieties possess all these features, but improved varieties are being produced by wheat breeders.
In choosing a wheat variety to sow, only rust-resistant varieties should be sown because stem rust is the major disease problem.
Frost damage causes great losses in production. No variety has high resistance to frost, although the winter wheats, like Winglen, are less affected. Late-maturing varieties suffer less from head frosting. Quick grazing of vigorous crops can reduce frost damage by delaying maturity. Early varieties which have been badly frosted may be cut for hay.
From year to year, the popularity of wheat varieties changes. In the 1971-72 season, the four leading New South Wales varieties were Mendos, Gamenya, Gamut and Falcon, but these varieties are now much less important. Current favourites are Kite and Shortim among the hard wheats for which premium prices are paid, and Egret and Condor among the soft wheats.
It is hoped that more hard wheat varieties which produce flour of strong baking quality will be grown in southern New South Wales and Victoria than has been the case in the past.
An important change in the wheat industry has been the zoning of the wheat producing areas. It is possible that in the future some growers may be paid less for their grain if they grow certain varieties that are not recommended.
Very great advances can be expected from the efforts of wheat breeders. It may not be long before varieties are produced which are resistant to all the common diseases, and which have much higher yield than present varieties.
The protein percentage of wheat grain is an important matter, for high protein not only increases the nutritional value of the grain, but it makes better bread.
The protein percentage of wheat depends on:
1. The variety grown.
2. The season; a season which is dry towards the time of harvest leads to a higher protein percentage.
3. The most potent factor is the level of soil nitrogen. Since legumes add nitrogen to the soil, wheat grown on pasture leys will produce grain with a higher protein percentage.
The average protein content of wheats of the Songlen type in the northwest of New South Wales is 13 per cent, whereas the average protein content for wheats in parts of the Riverina might be 11 per cent. However one sample of wheat grown near Junee tested 19 per cent protein, but it had been grown on an old pasture.
Biscuit manufacturers desire wheat with very low protein because this means that the biscuit dough will not rise like bread dough. Not only do they prefer certain varieties but they get much of their wheat from farms in the irrigation areas.
Diseases of Wheat:
Root rots are very serious diseases of wheat. They may be caused by many species of soil fungi. In a lightly affected crop, there may be no visible signs of the disease, except a slight reduction in yield. In seriously diseased crops no grain at all will be formed. Affected crops may show a pinkish discoloration at the base of the stem of mature plants, but in other cases the plant is wholly destroyed in its early stages.
Root rots seem to be worse in some heavy soils than in the lighter soils. A most important discovery is that root rots seem to be worse when a crop is grown on a ploughed-up pasture. The only way of maintaining the fertility of our wheat lands is to introduce a pasture phase into the rotation, and yet this seems to result in increased root rot attack.
Stem rust is caused by a fungus, Puccinia graminis triticum. Unfortunately there are a number of different strains of this fungus, each strain having different powers of infecting wheat. New strains of the fungus appear from time to time. A plant breeder may produce a variety which is resistant to all known strains of stem rust, only to find that a new strain of the fungus has appeared which can attack the new wheat variety. This is why progress in wheat breeding has been slow.
Stem rust spreads by means of microscopic wind-blown red spores called uredospores. These fall on a healthy plant, germinate in the dew, and a fungus thread, or mycelium, enters the plant. Here it spreads among the cells, obtaining nutrients from them. Eventually threads of the mycelium gather together under the epidermis and burst through it.
New uredospores are formed at the tips of the mycelium, and this gives the appearance of rust-coloured spots or streaks on the surface of the plant. These uredospores are blown away, and may infect other plants. The rust fungus can only cause serious attacks if the seasonal conditions are favourable to it.
Moist days in spring help the disease to spread. During winter the fungus stays alive as a parasite in native grasses of northern Australia, and the wind-blown spores are carried south again in spring each year. Heavy infection with rust greatly reduces the yield of grain, and moderate attacks result in pinching of grain.
General Management of Wheat Growing:
The ideal seed bed for wheat is one in which there is a layer of fine compacted soil about 6.3 cm below the surface. The implements needed to produce a good seed bed will vary with the soil type. In the Riverina, the process usually begins with disc ploughing and periodic cultivation to work the soil down to a suitable condition.
Rain often causes the surface to cake over, rendering more cultivation necessary. In the heavier soils of the north-west, the amount of cultivation needed varies with the previous history of the paddock, but in certain cases, very little is needed.
The preparation of the seed bed should be only the last event in a long plan aimed at conserving soil water and nutrients. Water is conserved by removing weeds, and by keeping the soil in a rough open state to increase infiltration. The length of fallow needed to conserve water will vary with the rainfall.
All over Australia, land under wheat loses water faster than the natural intake from rainfall. This shows how necessary it is to build up water reserves in the land before sowing wheat. In a Queensland experiment, enough rain was conserved by a summer fallow to grow a 2.5 tonne crop, even though no rain at all fell during the growth of the crop.
Fallowing mobilises the soil nitrogen, but it destroys structure and leaves the land open to erosion. Therefore the modern trend is to avoid long fallows and to use short rotations.
It is possible that greater use will someday be made of irrigation water for wheat crops in those areas where underground water is available.
Nutrients can only be restored to wheat lands by including a pasture phase in the rotation.
Seed wheat should be dusted with a fungicide to discourage the growth of disease-causing fungi. It should be free of weed seeds, and contain no broken, sprung or shot grains. Seed is usually graded before sowing.
Seed wheat is drilled in with a combine at a depth of about 5 cm. On heavier soils it is sown deeper. Unless there is rain, seed sown too deeply will probably malt, making a second sowing necessary. If sown at the right depth, the grain stays dry until rain falls.
The time of sowing varies with the variety and the climate. Late- maturing varieties, like Songlen, are usually sown early—in April. Mid-season varieties, like Condor, are sown in May, and early-maturing varieties, like Olympic, may be sown in June.
The rate of sowing varies with the fertility of the soil, rainfall and variety. Early-sown crops have longer in which to tiller, and may be sown lighter.
Some varieties such as Shortim tiller very strongly and should therefore be sown more lightly. Poor soils lead to weak tillering, and a heavier seeding rate is necessary. If grains are uneven in size, or ungraded, the rate is increased. Early-sown late varieties are usually sown at the rate of 55 kg per hectare, mid-season varieties at 55 to 66 kg, and late-sown wheats at 66 to 71 kg per hectare.
Superphosphate is commonly applied at sowing at the rate of 61 to 92 kg per ha. Nitrogenous fertilisers such as anhydrous ammonia may be used to a greater extent, especially on irrigated crops.
The combine sows grains in rows 15 cm apart, and applies superphosphate at the same time.
Crops are sometimes harrowed with spike harrows before the wheat is up, or until it is in the two-leaf stage. This is done to control weeds and may not damage the wheat very much.
If the crop becomes too leafy at an early stage, it may be fed off by stock. Grazing a crop has the effect of stimulating tillering, but must be carefully controlled, otherwise a reduction in yield can be expected. If weed growth is very strong, the crop may be sprayed with weedicides.
Boom sprays or aerial spraying may be used after the plants have reached the four-leaf stage. Spraying must not be done at flowering, but wheat has another resistant period when the grain is in the dough stage.