Everything you need to learn about growing vegetables in Australia:- 1. Introduction to Vegetables 2. Climate Required for Growing Vegetables 3. Soil Required 4. Quality of Seed 5. Soil Preparation 6. Transplanting 7. After Care 8. Diseases and Pests.
Introduction to Vegetables:
Green vegetables are an important item of human diet. Vegetables such as potatoes, turnips, carrots and parsnips are rich in carbohydrates, while beans and peas are rich in proteins. Many vegetables supply useful minerals, and the green leafy vegetables contain the important A and C vitamins.
Vegetables are produced in large quantities by market gardeners, orchardists and growers who specialise in field crops like peas, carrots and potatoes. Seed merchants grow vegetables only for seed production, and some growers specialise in producing seedlings for sale. Large quantities of vegetables are grown in home gardens, but this is seldom efficient production.
Vegetables may be classified according to the part of the plant which is eaten. Root vegetables include parsnips, carrots, sweet potatoes and radishes. The potato is a tuber, and the onion a bulb. Kohlrabi and asparagus are stems, while rhubarb and celery are leaf petioles. Lettuce, cabbage and spinach are leafy vegetables. Broccoli and cauliflower are inflorescences. Vegetable fruits include the tomato, cucumber, squash and pumpkin.
Climate Required for Growing Vegetables:
Vegetable growers should know a lot about the climatic needs of their crops, so that they can choose crops best suited to local conditions. If vegetables are grown in unsuitable climates, occasional failures are certain. On the other hand, if the vegetable is given ideal conditions, it is possible to know almost to the day when it will be ready for sale.
The three most important factors of climate are – temperature, water and day length. The supply of water is an essential factor, and vegetable crops are not successful unless they are irrigated or are grown in areas receiving a satisfactory rainfall.
Temperature is so important in vegetable growing, that crops are classified as frost-sensitive, moderately hardy and frost-hardy vegetables. Tomatoes, French beans, cucumbers and sweet potatoes all require high temperatures for satisfactory growth, and are easily killed by frost. These crops require a mean summer temperature of more than 21°C.
Crops like lettuce, carrots, peas and potatoes are fairly hardy in frost, and grow best with mean temperatures of 13 to 18°C, and do not do well at higher temperatures. Thus lettuce tends to develop a bitter taste and to go to seed at temperatures between 21°C and 26°C, while tuber formation in potatoes is at a maximum when soil temperatures are about 18°C.
Frost-hardy vegetables, like cabbage, turnips, spinach and onions, are not harmed by frost at all, and generally require cool temperatures to make maximum growth. Thus optimum temperatures for spinach and turnips are 10 to 15°C, and for cabbage 15 to 21 °C. Temperatures over 15°C will cause bolting in spinach. The temperature needs of each vegetable are different, and these must be studied if success is to be achieved.
Thus, although onions require cool conditions for early growth, higher temperatures are needed later. At temperatures between 10 and 15°C no bulbing occurs at all; between 15 and 21°C bulbing occurs, and the tops stay green; but between 21 and 26°C bulbing occurs and the tops die off properly.
Some vegetables are very sensitive to day-length changes, and this must be taken into account when planning the time of sowing. Thus, early onions need a 12-hour day in which to mature, but late onions need a 15-hour day.
Soil Required for Growing Vegetables:
Soils must be friable and easily worked; they must contain enough water, and have good drainage. A high content of organic matter is desirable in vegetable soils, and the soil must be of the correct acidity or alkalinity to suit the vegetable being grown. Plants like beetroot, cauliflower, parsnip, rockmelon and spinach are very sensitive to acid conditions in soils, and if necessary, lime must be added.
Vegetable soils must be fertilised to make sure that the necessary nutrients are present. As with so many other crops, soil nitrogen is probably the most important nutrient. Superphosphate and ammonium sulphate are usually added, and in coastal districts, potassium nitrate is also needed. In some districts molybdenum must be supplied, usually in the form of sodium molybdate.
Quality of Seed:
It is extremely important that vegetable seed be of the highest quality. In the first place, the variety chosen should suit the district. The seed should be clean and free of weed seeds, and it must have high germinating ability. Germination tests can be made quickly if the age of the seed is in doubt.
A tremendous amount of money has been spent on producing new, high-yielding varieties of seeds. Although these seeds may be very expensive to buy, it is foolish not to use them if vegetables are being grown for profit. For example, the new Japanese hybrid cabbage seed like K-K cross and K-Y cross is very expensive, but the seeds produce large, evenly-sized cabbages that are far superior to older varieties like Drumhead, Succession and Vanguard.
Vegetable seed must be free of disease. If seed is obtained from a well-known firm, it is likely to be free of diseases. Nevertheless, it is a common practice to use various fungicide dusts to control disease-causing organisms.
Thus copper-containing dusts are applied at the rate of one teaspoonful to each 500 g of seed, and dusts containing mercury at the rate of one-quarter to one-half a teaspoonful to every 500 g of seed. Some vegetables of the family Cruciferae cannot tolerate the presence of copper, and these seeds are usually steeped in hot water at 10°C for times ranging from 15 to 25 minutes.
Soil Preparation:
On vegetable farms the preparation of the soil begins as soon as the previous crop is removed. If a green manure crop has been grown, it should be disced and ploughed under in a succulent condition. In this way, nutrients will be quickly available to the next crop.
When the soil is at the right moisture content, the land is ploughed deeply. Large quantities of animal manures are then added. A 3 cm dressing of animal manures is equal to about 75 tonnes per hectare. Fruit vegetables, like the tomato, are usually given 10 tonnes of manure per hectare but leafy vegetables are given amounts up to 40 tonnes per hectare. It may also be necessary to add lime to the soil. Final harrowing will work down the surface of the soil to a suitable condition for sowing or planting out.
On well-managed vegetable farms rotations are used, but it is often difficult to plan a good rotation because so many things have to be taken into account. Shallow-rooted plants, such as lettuce, should be rotated with deep-rooted plants like melons. There is much tramping down of the soil in growing crops like beans and peas, and these crops should be rotated with crops like carrots and melons where tramping is much less.
Crops which have different pest and disease problems should be rotated. Crops with different requirements of organic matter should be rotated. Thus leaf, root and fruit crops should follow one another, and care should be taken to avoid growing two consecutive root crops in the soil.
Transplanting:
The following plants are usually not transplanted in commercial vegetable farms, but are sown in their final positions; beet, spinach, beans, parsley, corn, peas, carrots, parsnips, turnips, potato and radish. The following vegetables are normally raised in seed beds, and later transplanted to their final positions; cabbage, cauliflower, broccoli, celery, brussels sprouts, lettuce, tomato and onions.
Transplanting must be carried out properly if the seedlings are to survive. This operation is best done on a dull day with no wind. Seedlings should be hardened off a week before transplanting. If deprived of surface water, seedlings respond by making deeper root growth and more root branches. Such plants have a better chance of survival after being moved.
In hot districts the seedlings are sometimes given a better chance of survival by pinching out one or two of the larger leaves. The roots are then given a chance to grow before a large leaf area develops. Transplanted seedlings are usually watered in, and may be shaded until established.
After Care:
Growing crops must be kept free of weeds, irrigated when necessary, and may have to be sprayed for the control of pests and diseases. The spacing of rows is usually arranged so that inter-row cultivation and spraying can be done by using tractors.
The harvesting of vegetable crops is largely governed by seasonal conditions. Crops like green peas and sweet corn ripen very quickly in hot weather, and unless several plantings have been made, it may be impossible to harvest all the crop at the best time. Mechanical methods of harvesting are the most efficient.
All vegetables must be prepared properly for market. Vegetables like cabbages and lettuce may require very little preparation, but root crops like carrots, parsnips and beetroot must be topped, cleaned and marketed in the right type of bags.
Diseases and Pests of Vegetables:
Steps must be taken to control pests and diseases in vegetable crops, or yields will be seriously reduced. Insect pests not only eat the foliage, but may also spread virus diseases. There are two chief types of insect pest; those which eat leaves, and those which suck out the plant juices through long tube-like mouthparts.
Leaf eaters, like the caterpillar of the cabbage white moth, are controlled by spraying the plants with a stomach poison such as lead arsenate. Leaf- sucking insects, like the green vegetable bug, are controlled by spraying or dusting the crop with contact insecticides such as Malathion or Maldison.
Fungous diseases of vegetables may be controlled by using disease- resistant varieties, if these are available, or by spraying crops with fungicides, like Benlate. Digging out infected plants may help to control the spread of these diseases.
Virus diseases of vegetables are often serious. For instance, bronzy wilt of tomatoes causes the bushes to die back from the tops, and no fruit is produced.
These diseases may be controlled by the following methods:
1. By using virus-resistant varieties, if these are available.
2. By controlling the insects responsible for carrying the virus on their mouthparts to healthy plants.
3. By digging out all infected plants.
4. By altering sowing times to miss the season when the insect vectors are present.
5. By using the highest quality seed which is guaranteed to be free of virus.
In most cases of insect and disease attack, healthy vigorous plants suffer less, so good management can lessen these problems.