Everything you need to learn about growing lucerne in Australia:- 1. Introduction to Lucerne 2. Botany of Lucerne 3. Genetics of Lucerne 4. Climate 5. Nutrition 6. Crop Enemies 7. Management.
Introduction to Lucerne:
Lucerne, Medicago sativa, is sometimes called “the king of fodder plants”, for not only does it produce a large amount of high quality stock food, but it is drought resistant and has a long life. In America it is known as purple medic or alfalfa.
Lucerne is thought to have originated in south-western Asia and was first grown as a forage plant in Iran. From there it spread to the Mediterranean countries of Greece, Italy, France and Spain. The Spaniards took lucerne to South America and Mexico in the late sixteenth century. It is now an important forage plant in southern Europe, the Americas, Canada, North and South Africa and Australasia. Argentina has the largest area under lucerne—1.7 million ha—while France and the United States of America each have about 1 million ha.
In Australia, lucerne is grown in different ways in different districts. On the best alluvial flats near Tamworth, Maitland, Mudgee and Canowindra, lucerne growing is specialised. The crops are irrigated and cut for hay six or eight times in the year.
Second-class lucerne areas are on deep soils which receive a good summer rainfall. On the Darling Downs, Liverpool Plains and parts of the north-west of New South Wales, deep black soils grow good lucerne which can be cut for hay two or three times a year or more.
Lucerne is also used as a legume rotation on wheat lands receiving 508 mm of rainfall. Occasionally growth is sufficient to provide one good cut for hay, but the crop always provides good grazing.
In the drier pastoral areas of eastern Australia, lucerne is sometimes broadcast thinly, but only provides some grazing. Lucerne hay is one of the chief drought fodders in Australia.
Botany of Lucerne:
There are many varieties of lucerne, each with special characteristics. The common erect varieties of lucerne are perennial legumes which may live for as long as 15-20 years.
Lucerne is noted for its drought resistance and this was once thought to be due to the deep-rooted nature of the plants. While the roots do go down 6 to 9 metres in certain soils, research has shown that the roots of most lucerne plants are confined to the top 60 to 90 cm of soil. Therefore it seems that the growth of most lucerne is as dependent on seasonal rains as most other crops.
As the plants age, lucerne roots eventually become rather thick, and serve to store food as well as to obtain water and nutrients. The crowns are the tops of the roots, from which 5 to 20 thin stems arise. As stems are removed by grazing or cutting, more will arise from buds on the crowns.
The stems are 60 to 90 cm in height, and may branch. They are soft when young, and being thin, can be readily dried out in the making of hay. Lucerne leaves are arranged alternately on the stem, and stipules are found at the base of the petioles.
The leaves are trifoliate, the centre pinnule being carried on a short stalk. The outer one-third of the leaf margin is toothed, and the midrib of each leaflet is extended at the margin into a minute spine. When lucerne is growing vigorously, as much as 40 per cent of the weight of the plant may consist of leaves.
The inflorescence is a raceme of pea-shaped flowers which is formed in the axils of the upper leaves. Each flower has a short pedicel, five sepals and five petals. The petals are not identical. The large standard petal stands at the back of the flower.
On both sides are the two wing petals. Between the wings are the two fused keel petals, fused along the base only. The keel encloses the reproductive parts. The ovary, containing the ovules, ends in an upcurving style and stigmatic tip.
The ovary is surrounded by ten stamens, nine of which are fused together by their filaments. In the unopened flower, the stigma is pressing upwards against the closed keel petals. In order to be pollinated, the flower must be tripped, which means that slight pressure on the keel will release the imprisoned ovary and stamens. The exposed stigma may then receive pollen, and at the same time the stamens are shattered and pollen made available for another flower.
The tripping is normally done by insects, and the honey bee can do it well. If insects are not available, few flowers will be fertilised, although some may be tripped by the wind or by raindrops. The flowers may be tripped artificially if a horizontal bar mounted low on wheels is pulled over the crop. The bar hitting the flowers causes tripping to take place.
After fertilisation, the petals drop off and the ovary swells and becomes twisted, turning into a coiled pod containing from one to eight small kidney-shaped seeds. Seeds may be olive-green or yellow-green. If seed is not harvested, the pods soon split open and the seed falls to the ground.
As with any other crop, the main factors which influence the success of lucerne production are genetics, climate, nutrition, diseases and general care and management.
Genetics of Lucerne:
The variety of lucerne which has been grown most commonly in Australia has been the Hunter River variety—an erect form of lucerne. It is now realised that there are many varieties of lucerne and in recent years interest has taken in other varieties of this plant.
Creeping rooted lucerne is a prostrate variety which seems to be more drought resistant than erect varieties and to tolerate defoliation better. In an Australian experiment, after 16 months of continuous stocking and grazing, only 8 per cent of Hunter River lucerne plants were still alive, but 66 per cent of a creeping variety was still alive after the same treatment.
In Australia we have thought of lucerne as a summer growing plant which is dormant in winter. There is however winter growing varieties such as Hairy Peruvian and African lucerne which may find a place in our agriculture.
Climate Required for Growing Lucerne:
Varieties of lucerne can be found which can live under a wide range of climatic conditions. While some varieties can live in temperatures of 49°C, and others can survive temperatures as low as -52°C, most erect varieties are best suited to temperate climates.
Erect lucerne grows well in hot dry climates if irrigation is possible. It is capable of withstanding prolonged dry periods, but it will not yield well in drought.
Lucerne is a light-loving plant. Shading of the plant means that there will be less root growth, fewer nodules formed and a low amount of protein made.
Very high temperatures reduce the number of flowers formed, but the effects of temperature on lucerne depend on the amount of light and whether the plant is cut.
Lucerne is a long-day plant. This means that long days lead to a higher yield of plant material and to the formation of more flowers.
Nutrition Required for Growing Lucerne:
Lucerne needs adequate supplies of soil water, yet cannot stand waterlogged conditions, or a high water table. It is best adapted to deep loam soils, or heavier soils with porous sub-soils. The potassium, sulphur and calcium content of soils is important to lucerne.
If potassium is deficient, white dots occur on the leaflets near the margins. If sulphur is deficient, the leaves tend to be pale yellow-green. Soils should be well supplied with calcium.
The most important soil characteristic is that it should allow nodulation to occur. The soil must contain the correct strain of Rhizobia. If these bacteria are not present, they must be added to the soil, either with the seed, or separately. In certain districts, such as parts of the southern tablelands of New South Wales, lucerne will not nodulate, even when the seed has been properly inoculated.
Here the reason may be that the soils are too acid for bacteria to survive. In other districts, there may be no apparent reason for failure to nodulate, but it is possible that soil fungi make an antibiotic substance similar to penicillin, which kills the Rhizobia as soon as they are put into the soil. More research is needed in problems of nodulation.
Crop Enemies of Lucerne Seeding:
Because the lucerne seedling is not a very strong or vigorous plant, weeds may prevent the successful establishment of lucerne. Weeds may also be a problem in the growing crop, but the expected profits from the lucerne crop must be considered before deciding to spend money on weed control.
Easily the worst problem for lucerne growers has been the recent attacks of aphids, especially the blue-green aphid. The best solution to this problem seems to be to find varieties of lucerne that are resistant to these pests, like the new variety CUF 101.
Other bad pests of lucerne are the lucerne flea (Sminthurus sp.) and the red-legged earth mite (Halotydeus sp.), although nematodes, the corn earworm and other insect pests may be a problem.
The commonest fungus disease of lucerne is the leaf spot disease, but this does not usually cause much damage.
General Management of Lucerne Growing:
Since lucerne seed is so small, it is necessary to produce a fine seed bed before sowing. It is usually necessary to work the soil well with gangs of disc harrows until weeds are removed, and the surface is reduced to a fine condition. Cloddy surfaces may need much more cultivation than sandy alluviums.
Seed is sown with a drill at a depth of one to two cm, although some success can be obtained by broadcasting the seed, followed by harrowing. Seed must not be sown too deeply.
In order to bring moisture to the surface around the seed, it is usual to roll the paddock after sowing. Alluvial soils are sown at the rate of 11 to 16 kg/ha, but 7 to 11 kg is sufficient for drier areas. In very dry districts, seed is sown at 2 or 3 kg/ha.
The greatest care should be taken with establishing a good stand of lucerne, since it can be expected to last a long time. Autumn sowing is found to be better than spring sowing for most districts.
The young seedlings do not grow very fast during the winter, but they have made a good start by spring, and will grow fast then. The danger in spring sowing is that young plants will not have a deep enough root system to help them through a hot dry summer.
Lucerne should not be cut or fed off until it is properly established.
The plants can recover from the removal of the tops, but their ability to do this depends on how often the leaves are removed and how quickly more shoots can be produced by the crowns. The crowns can only make more shoots if the roots are functioning well.
Cutting or grazing has marked effects on the roots, for root growth may cease, root hairs may die and root nodules may rot away. Therefore it is clear that a vigorous root system is needed before heavy cutting is begun.
When well grown, the plants begin to flower in the warm months, and cutting can begin. As the plants age, they pass through the same stages of changing food value as the grasses, that is, the protein percentage falls and the fibre percentage increases. When the stems carry many leaves, the protein content is high; but as the leaves become less green and begin to drop, their protein and vitamin A content falls.
It is therefore desirable to cut lucerne when the stalks are carrying the maximum number of leaves, for then the protein and vitamin A content will be high, and the fibre content low. This stage is reached in the early stages of flowering, when less than half the plants are in flower.
After cutting, the lucerne is left to lie on the ground until it is dry. On very hot summer days, it may dry out in a few hours, but in humid districts the process may take some days. In some coastal districts lucerne hay cannot be made at all, because stalks cannot be dried properly.
If the lucerne is too dry, it cannot be handled because the leaves—the most valuable parts—will drop off. Usually this hay can be picked up if left overnight, for the dew softens the leaves and they adhere to the stem while damp.
In most cases lucerne hay is baled, as this process makes it more compact for storage and easier to transport without damage. Modern pick-up balers collect the hay from the windrows, and bale it as they move along. The bales are usually stood on end to dry out further before storing. On opening a bale of prime lucerne hay, the hay inside the bale is green and carries many leaves.
There should not be any signs of mildew or discoloration. Inferior hay loses its colour, is very stalky, has few leaves and may be mouldy or otherwise spoiled. In cold districts lucerne should not be cut heavily in late autumn. This practice may prevent the roots from storing enough food to carry the plant through the winter.
Many lucerne growers are becoming interested in harvesting the crop for seed, because the use of modern methods can lead to very high yields. It is best not to use the first spring growth for seed, but to begin by cutting this crop.
This removes weeds and the early spring growth which may be uneven. The strong regrowth can produce the seed crop. More seed can be produced if the crop can be irrigated at intervals, but rain or irrigation has the greatest effect if it occurs near flowering.
Harvesting usually occurs two to three months after flowering, but it must be done at the right time. A slight delay may result in most of the seed dropping to the ground. Harvesting must also be done at the right time of day—early morning—to avoid shatter of the pods and loss of seed. Harvesting may be done when half to three-quarters of the pods have turned brown.
High yields cannot be obtained unless a high percentage of the flowers have set seed. A flower will not form seeds until it has been tripped, and this is normally done by insects. Experiments in South Australia have shown that, by putting bee hives among the lucerne, more flowers are tripped and set seed.
The use of insecticides to control insect pests may sometimes result in the killing of bees. It has been found that tripping of a high percentage of flowers can be brought about by pulling through the crop a long horizontal bar mounted low on wheels.
Because of poor management, the average Australian yield of lucerne seed is low and may be less than 112 kg of seed per ha. This should be compared with yields of 1100 kg per ha which have been obtained in parts of South Australia, and yields of over 1200 kg per ha in California.
It is essential that lucerne be irrigated if the best yields are desired. A reliable creek or river, or large dam storage must be available. Spray equipment must be easily moved over the fields, and the soil must not be harmed by irrigation. In all cases, a rain gauge should be placed on the ground under the sprays, so that the quantity of water applied can be measured accurately. Over-watering must be avoided.