In this article we will discuss about:- 1. Production of Fruits 2. Climate Required for Fruit Cultivation 3. Soil Conditions 4. Varieties 5. Pests and Diseases 6. Orchard Management 7. Harvesting and Storage.
Production of Fruits:
The production of fruit is an extremely important part of Australian agriculture, and the industry has the following branches:
1. Fresh fruit – citrus fruits, apples, pears and cherries, the stone fruits, tropical fruits and grapes.
2. Preserved fruit – canned pineapples, peaches, apricots, cherries, berries and tropical fruits, fruit juices, jams.
3. Dried fruits – sultanas, raisins, currants, apricots, peaches and pears.
4. The wine-making industry, and table grapes.
Australian exports of dried and fresh fruits totalled $50,000,000 in the 1976-77 season.
Climate Required for Fruit Cultivation:
Dried fruits can only be produced in those areas having a Mediterranean climate with hot dry summers. Therefore this branch of the industry is confined to parts of Victoria, southern New South Wales, South Australia and Western Australia. Leeton, Renmark and Mildura are large centres of production. Australia ranks third in importance as a world producer of dried fruits.
Tropical fruits, such as avocados, mangoes, paw-paws, bananas and pineapples, can only be grown in the hot humid coastal areas of Queens-land and northern New South Wales. All these fruits are damaged by frosting.
Apples, pears and cherries are grown best in cool highland districts, such as those of Batlow, Orange and Kentucky in New South Wales, and the Granite Belt in south Queensland. Winter cold is important for deciduous fruit trees.
In districts where there is not sufficient winter cold, leaves may appear late and blossoming may be spread over a long period. The setting of fruit and the final production will then be lowered.
Citrus fruits require ample sunshine and water, and must be grown in areas not subject to heavy frosts. They are grown successfully in the irrigation areas of Victoria and New South Wales, at Gosford near Sydney, and in the Lockyer Valley in Queensland.
Stone fruits are chiefly grown in the irrigation areas where there is abundant water, hot dry summers and freedom from spring frosts.
Soils and climate have a very big effect on the quality of wine made from grapes, and so the wine-making districts are widely separated. Good wines are produced in parts of the Hunter Valley, in New South Wales, the irrigation areas of Victoria, and in the Barossa Valley and other parts of South Australia. Table grapes can be grown successfully in districts where stone fruits do well.
Soil Conditions Required for Fruit Cultivation:
Fruit trees are very sensitive to unfavourable soil conditions, and many characteristics of a soil may be important. Probably no soil feature is more important to fruit trees than good drainage, for while there must be an ample supply of soil water for high production, fruit trees are easily killed by waterlogging. Great losses have occurred with citrus trees grown in poorly drained coastal soils around Sydney, and wet soils have also killed out many peach and plum trees in parts of Victoria.
Because drainage is so important, the texture and depth of a soil affect growth and production of fruit. Thus most citrus trees grow best in well-drained sandy soils or sandy loams. They may be grown in heavy-textured soils provided that the structure is good. Apple trees should be planted in deep soils if sturdy trees are desired. Stone fruits generally do better in light-textured soils, but can be grown in clay loams of good structure.
In soils where there is impervious clay subsoil, drainage may be improved by laying porous pipe drains, or by the use of subsoil ploughs. A method used in Victoria consisted of blowing chopped-up crop residues into channels made in the subsoil by a special sub-soiling implement. These residues keep the channels open and allow water to drain away through the subsoil.
Steps taken to maintain the supply of soil water vary greatly with the district. In moist coastal districts, very little water may be needed except in the case of young trees in mid-summer. In orchards of the dry inland, irrigation water may be applied. Successful experiments have been made with the use of straw spread over the ground as a surface mulch.
These mulches prevent loss of soil water by evaporation, but they are so efficient that, in some areas, they may lead to waterlogging of the soil. Straw mulches keep down weed growth, but will not prevent couch grass from growing.
Some growers keep a clean bare fallow between their trees, believing that all other plant growth will steal water from the trees. In other districts, growers sow pasture plants between the trees, but they may control these plants by mowing them. The only rule about plant growth between fruit trees which seems to be important in all districts is that weeds must be removed from around young trees.
It has been shown that the supply of soil nutrients must be ideal if strong tree growth and high yields are desired. This applies to the minor as well as to the major plant nutrients.
Many plant nutrients are supplied in the form of inorganic or organic fertilisers. Studies of the effect of different fertilisers on the shoot growth of young Granny Smith apples have shown that fowl manure at the rate of 1.3 kg per tree was superior to a mixture of superphosphate, ammonium sulphate and potassium nitrate at the rate of 340 g per tree.
Studies have shown that applications of up to 3.5 kg of mixed fertilisers to each well- grown apple or peach tree produce greatly increased yields. It is now common practice in some districts to apply 2.7 kg of mixed fertilisers in spring, and a further one kg of ammonium sulphate in December.
Deficiencies of trace elements must be corrected. Zinc may be supplied in the form of foliage sprays of zinc sulphate. Deficiencies of boron and other elements are usually corrected by adding chemicals to the soil.
There is no perfect plan of orchard soil management, but methods must be found which are suited to local conditions. The roots of fruit trees will come to the surface if they can, and a better growth of the tree will result if the roots are allowed to feed in the surface soil. Therefore any system of soil management which includes cultivation will reduce the surface growth of tree roots.
The chief systems of soil management are:
1. Clean cultivation, with shallow working of the soil.
2. The use of straw mulches 7-10 cm thick.
3. The establishment of perennial pasture plants which are mowed to control excessive growth.
4. The use of annual legumes, such as sub clover.
5. The growing of green manure or pasture legumes, which are ploughed under the soil.
In each case, fertilisers must be applied to the soil, but lighter applications of nitrogenous fertilisers may be made under some systems of management.
Varieties of Fruits:
The fruiting variety chosen by a grower will be that one which has the following qualities:
1. Unites well with a given rootstock.
2. Has the desired maturity.
3. Is a popular variety for which there is a good demand.
4. Can be cross pollinated by other varieties in the orchard. Cross pollination is important in apples, pears and cherries.
An orchard tree usually consists of the fruiting wood of one variety, called the scion, which has been grafted onto the root system of another variety called the rootstock. Rootstock varieties are chosen because they are vigorous, produce regular crops, and because they are resistant to soil parasites or unfavourable soil conditions.
However, some rootstocks do not combine well with some scions, so the grower must first choose a satisfactory rootstock to suit local conditions, and then choose a variety which combines well with it.
If the orchardist buys his young trees, this choice has already been made. Much progress is now being made in the choice of better rootstocks for fruit trees. Northern Spy rootstocks produce good apple trees, while Keiffer stocks are satisfactory in pears, and Elberta rootstocks in peaches.
Plum rootstocks are useful for peaches and apricots which are being grown in wet soil conditions. Rough lemon, sweet orange and trifoliata rootstocks are used widely in citrus culture.
Pests and Diseases of Fruits:
Much of the expense concerned with producing fruit comes from the need to control various pests and diseases. Insect pests, such as woolly aphis, codling moth, pear-root aphis, fruit fly, peach-leaf aphis and the various scale insects of citrus trees cause great annual losses.
The methods of controlling insect pests vary, but some general methods of control are as follows:
1. The use of quarantine areas. All pupils of agriculture should know that some insect pests have been kept out of certain fruit-growing areas by the use of quarantine methods. Thus it is forbidden for anyone to take any fruit into the Murrumbidgee Irrigation Area, unless it has been carefully examined by inspectors, and perhaps treated with an insecticide. Pupils should learn to respect the quarantine rules, for these help to prevent the spread of pests like phylloxera and fruit fly.
2. Attack by insects can be lessened by preventive spraying provided that this is carried out early enough. Thus the newer phosphorus sprays can kill the peach-leaf aphid at an early stage when the leaf buds are just opening. If there is much delay in spraying, the aphids may destroy the young opening buds.
3. Control measures during the fruiting season can lessen the attacks of insects. Thus, only a constant watch for pests and continued treatment with sprays like Lebaycid can control fruit fly and the codling moth.
4. The use of resistant varieties. For instance, certain apple and pear rootstocks are resistant to woolly aphid attack.
Fungous diseases, like curly leaf of peaches, downy mildew of grapes, powdery mildew of apples and the various root-rot diseases are just as serious as attacks of insect pests. Spraying with fungicides at the proper time is the chief method of control. Some root-rot diseases may be avoided by using root-stocks of a resistant variety.
Orchard Management:
Orchard management is efficient when up-to-date methods are used for carrying out the main operations, like raising young trees, planting out, pruning, spraying, harvesting and storing.
Most growers buy young trees from nurseries, but there are advantages in raising trees on the farm. In all cases, the site chosen for a nursery should be warm, sheltered and free of frost danger, and the soil must be well drained.
Rootstock seedlings are first raised, transferred to nursery rows and then budded with the chosen scion variety. Young citrus trees ready to plant out can be produced in three years.
Systems of planting out vary in different fruits. Trees may be planted on the square system, on the triangular system, or contour planting may be carried out. In many areas, older systems of planting are giving way to newer systems.
Thus in apple orchards, trees are being planted much closer together in the rows, the main purpose being to increase yields, to prevent wastage of costly sprays, and to allow more room between the rows for the bigger spraying machines which are now being used.
Trees must not be planted too close to each other, or pruning and harvesting may be slowed up. In citrus orchards planted on the square system, the modern tendency is to allow more room between trees, but another idea is to plant closely in rows to reduce costs of spraying and pruning. The actual planting distance is determined partly by the size of the mature tree, and experience is needed to know this in any district.
Citrus trees are not pruned, or are given very light pruning. The modern tendency in citrus planting is to plant in hedge rows to allow mechanical pruning to be done. Deciduous trees and grape vines are always pruned, but pruning methods are changing rapidly at present. The chief aims of pruning are to produce a strong framework, to increase the size and quality of fruit and to secure regular crops over long periods.
Systems of pruning make use of the following facts about tree growth:
1. The vigour of a shoot or branch depends on the number of leaves which it carries.
2. The more vigorous a shoot is, the less fruit it is likely to bear.
3. The fewer the buds on a stem or branch, the stronger is the growth from each one.
4. The shoots at the top of a tree are usually the most vigorous.
5. The smaller the number of fruits, the larger their size will be.
6. The closer a branch or shoot is to being vertical, the more vigorous it will be.
Systems of pruning apples vary widely, but certain new systems are becoming very popular. An older idea was to prune trees into a vase- shaped framework. In the modified central leader or MCL method, trees are pruned fairly lightly to one main trunk with branches which bend over as the fruit ripens.
By using this system of pruning and by planting 5189 trees to the hectare instead of the usual rate of 266 trees to the hectare, the CSIRO research station at Applethorpe in Queensland has produced yields of 9 tonnes to the hectare instead of the usual 5 to 7 tonnes. Moreover, this system has brought trees into full bearing within 4 to 6 years instead of the usual 10 or more years, using the older pruning methods.
Spraying of fruit trees is such costly work, and yet so important, that a great deal of work has been done to improve this operation. It is still very costly. Improved sprays, like Lebaycid, and Rogor, are now available, and they are more effective than older type sprays. Sprays like Zineb, Malathion, Quintozen and wettable sulphur are effective on aphids, mites and red spiders.
New spraying machines are now available which apply sprays quickly and more effectively. Spraying machines are now much larger, and may be of the high-volume or low-volume semi-concentrate type. Large quantities of water must be carried if the high-volume machines are used.
The ideal spraying operation applies the spray evenly without reaching the drip point which can be dangerous to the trees. The drip point may be reached when more than 840 litres of spray are applied to each hectare of dry trees.
Methods of using orchard sprays have widened and improved. Sprays are now used to control insects and fungi, to thin out fruit blossoms when these are too numerous, to apply certain trace elements, and as stop-drop sprays to prevent fruit dropping before the harvest. The substance 245TP is a valuable stop-drop spray, when used at the right strength.
Harvesting and Storage of Fruits:
A useful idea is to change the time of harvest slightly to avoid losses in certain kinds of fruit. Thus canning peaches may be picked early and ripened at a temperature of 34°C to escape brown rot.
Bulk handling methods are used in harvesting fruit. In one method, two large bins each holding one tonne are carried on a trailer along the rows. When full, the bins can be moved over rollers into the packing shed, thus saving a great deal of labour. Mechanical harvesting is being investigated in the hope that it may reduce the cost of labour involved in manual harvesting.
Losses caused by birds at harvest time are being reduced in some areas by the use of special balloons filled with hydrogen. The captive balloons swing about with the slightest breeze and frighten the birds.
Improvements in the storage of fruit have been of great value to the fruit industry. Losses in stored citrus fruits have been reduced by sorting, cleaning, dipping in detergent, rinsing, dipping in borax tank to kill fungi, drying and waxing. The use of diphenyl wrappers is an added safeguard against fungous attack.
Older methods of apple and pear storage relied on low temperatures alone. Newer storage methods make use of the fact that fruit cells continue to respire after picking; that is, they use up oxygen and give out carbon dioxide. If the carbon dioxide content of the air can be raised, the fruit cells do not breathe as quickly and last longer.
In one method, fruit is stored in cases lined with polythene sheeting. The carbon dioxide of the air inside these sealed cases begins to rise as the fruits respire, and this, together with the low temperature, causes the fruit to keep very well. Pears have been kept in good condition for two seasons by this method.