Temperate and Subtropical Fruit Production

David Jackson, Graham Thiele, Norman Looney, Michael Morley-Bunker, David Jackson, Graham Thiele, Norman Looney, Michael Morley-Bunker

• Editore: CAB International
• Anno: 2010
• ISBN:
  9781789248852
• Edizione: 3
• Argomento: Biological Sciences
• Categoria: Horticulture

Fully revised and expanded to include organic fruit production, this new edition provides a thorough introduction to the cultivation of fruit found throughout the temperate and subtropical regions of the world.

PART I

General Points on Fruit Husbandry

1 The Distribution of Fruits

DAVID JACKSON, NORMAN LOONEY AND MICHAEL MORLEY-BUNKER

The selection of fruits for any area depends on many factors, although, in the final analysis, the most important will undoubtedly be the climate. All climatic factors will be introduced and discussed in this chapter. The significance of climate will be re-emphasized in a separate chapter (Chapter 2) and in those sections describing specific fruits.

Present-day distribution of fruit production on a world scale is shown in Tables 1.1 and 1.2. Some tropical fruits, e.g. bananas, mangoes and papaya, are included for reference purposes. The increase in world production in fruit crops over the last 30 years is shown in Table 1.3. Many crops show an increase of between 100 and 170% in the last 30 years, although there are some anomalies; for example, production of plums has not doubled (i.e. increased by 100%) in the last 30 years, whereas tangerines, mandarins and clementines have risen by over 200%.

The usefulness of a fruit helps to determine its total production. Thus oranges, which are eaten fresh and made into juice, are much more widely grown than lemons, which are just as easy to produce and grow in similar areas. The difference is that lemons are not eaten fresh and have a more limited use in cooking and drink manufacture. Grapes have four uses – fresh, for juice, wine and as dried fruit – each of which is part of a large or considerable industry. Consequently, they constitute a major world crop. Bananas and apples are popular fruit that are very convenient for fresh eating. They also have important uses as processed products.

A more obvious factor influencing production and distribution is climate. Virtually all crops have specific climate requirements and production is highest where the climate is the most suitable.

The plant kingdom contains somewhere between 250,000 and 400,000 plant species. It contains a wide range of plant forms, but not all plant species are termed flowering plants – those plants that are classed as flowering plants are grouped into plant families and, again depending on the authority, there are somewhere between 150 and 400 flowering plant families. The number of plant families that contain commercially important fruit crop plants is comparatively very small. The number of plant species with known fruit crops may not be more than 500. The small number of fruit crops under cultivation relative to the number of plant species in the world may be a reflection of our lack of detailed knowledge of the world’s flora. Temperate fruit crops have tended to be predominant in lists of recognized fruit crops. The awareness of what temperate fruits exist may be more of a reflection of where commercial orcharding has developed. The identification of plant species in the tropics that produce desirable edible fruits and the development of those plants into commercial fruit crops are not complete. The importance of this lack of development of tropical fruit crops is that, as natural plant communities diminish, especially through deforestation, then potential fruit crops may be lost for human use – both humans in the tropics and humans elsewhere in the world.

Although the number of plant species used for fruit cropping may be small, the process of selecting different plants with different desirable characters has expanded the choice of crop plants to use. The entry on Wikipedia suggests that there are more than 7500 known cultivars of apples worldwide. Historically, growers might have called the selected desirable plant a ‘variety’, but the horticultural convention is that selected cultivated plants should be termed ‘cultivars’. Each cultivar is given a unique name. A cultivar should be distinct in at least one character which identifies it from other similar plants. That unique character must be consistent as new generations are produced through whatever propagation methods might be used. If that propagation method is asexual, meaning that the daughter plants are replicas of the mother plant, then the new plant can also be termed a clone. In theory, at least, a clone should be unvaryingly the same, generation to generation. However, there are small changes over time with asexual propagation. Cellular and tissue mutations do occur, and therefore, over time, some variation may be found in a clonal population. Orchardists may use the term ‘strain’ to identify progeny lines within a clone. Mutations of tissues can lead to whole organs having a distinct and different character. Plants can often be propagated from organs which are clearly different from the rest of the plant. The new plant will have the genetic composition of the mutated tissue and not the parent tissue. These plants are called ‘sports’. There are numerous instances when the ‘sport’ differs from the parent because of pigmentation change. Many red apple cultivars are sports of less coloured cultivars – this is the case for ‘Delicious’ and ‘Red Delicious’ and again for ‘Gala’ and ‘Royal Gala’.

Table 1.1. Distribution of world economic fruit crops (production in ’000 tonnes).

nes, not elsewhere specified or included.

Figures for 2007 (FAO).

Table 1.2. Distribution of world fruit crops, showing three foremost leading producing countries.

Figures for 2007 (FAO)

The development of fruit crops has been heavily influenced by successes in selecting and breeding new fruit cultivars. In Europe, in the 18th century, the realization that plants were sexual, and therefore that hybridization was feasible and manageable, led, in some crops, to a proliferation in choice of what to grow. However, more recently the organization of global markets and the management of delivery and retailing have tended to reverse this process. Although there may well be over 7500 cultivars of apple that could be grown, there are probably no more than 30 that are of notable commercial importance. Restricting the range of cultivars for cropping carries risks. A small genetic base could be overwhelmed by biological threats from pathogen and pest organisms. It may be fortuitous but modern gene analysis offers the opportunity to identify the range of genetically based characters in crop cultivars and what plants carry particular genetic traits. There needs to be a coordinated vision of what to collect to maintain the genetic heritage for future plant breeding of fruit crops.

Table 1.3. Increase in world production of selected fruit crops from 1977 to 2007. Data taken from FAO statistics 1977 and 2007.

^ano data for 2007, data from 2002 used for computation.

A number of factors that help to determine fruit crop distribution will now be considered. Many of these factors relate to climate and will be discussed further in Chapter 2, but other factors, such as soils, pests and diseases, and topography, are equally important.

Climatic Factors

Temperature

Temperatures increase as latitude and altitude decrease, and extremes are moderated in sites close to a large volume of water. Temperature is modified by geographic features such as slopes and wind currents that minimize the problem of ‘frost pockets’. It is profoundly influenced by mountain ranges that intercept rain clouds and create hot, dry deserts. Major modifications may be induced by ocean currents. The Gulf Stream warms peripheral areas of north-west Europe; the Humboldt (Peruvian) current cools the west coast of South America. Temperature is the major factor affecting the distribution of fruit plants.

Water

Traditionally, fruit crops were grown in areas where rainfall was adequate to maintain good plant and fruit growth, although irrigation has been known and used for thousands of years. In the 19th and 20th centuries its use increased dramatically, and today it is remarkable in its sophistication and efficiency. In areas with Mediterranean or continental climates, characterized by dry, warm–hot summers, water obtained from underground sources, dams or river diversions provides excellent growth conditions. Low rainfall and humidity, together with adequate irrigation water, provide good growth with low disease pressure. The opposite situation, regions with very high rainfall, is often avoided because of disease problems.

Relative humidity

High rainfall is usually associated with high relative humidity. Some crops, such as subtropicals, blueberries and cranberries, are best grown in humid climates, but most others do better under conditions of low humidity, provided the roots have adequate moisture. However, it must be kept in mind that water loss from evapotranspiration is greater in dry air, and situations can arise where wilting occurs even when soil moisture is considered adequate.

As mentioned above, humid conditions increase disease pressure. High relative humidity at critical stages of fruit development can induce russet and other blemishes on the fruit surface, but there are also positive effects. For example, Cox’s Orange Pippin apples develop superior skin texture when grown in a cool, humid climate.

Overall, while warm, humid conditions are conductive to rapid growth and early, high yields, high humidity can add significantly to the cost of production.

Light

Light levels vary with season, latitude, cloud cover and natural and manmade pollution. Generally, southern hemisphere countries have low pollution levels and, since the earth is closer to the sun in southern hemisphere summers than in northern hemisphere summers, light intensity is generally higher. It is usually the case that higher light intensity increases yield, since more leaves in the canopy are adequately illuminated. However, under clear conditions where there is little scattered light, only non-shaded leaves or parts of leaves receive adequate (and often excessive) illumination. In such situations it is not uncommon to see fruit damage from ‘sunburn’ and leaves performing poorly because of excessive light and heat. This reality must be considered when developing appropriate tree and vine management practices for various regions.

Wind

Regions and districts vary considerably in the amount of wind. Wind (as opposed to air movement) is seldom beneficial; it can inhibit tree growth and often destroy crops. As will be seen later, wind can be controlled to a considerable extent by shelter, and there are many places where, if other things are favourable, orchardists would be wise to erect shelter, artificial or natural, to improve a fruit production site.

Hail

Few areas are free of hail and, for some, hail is a perennial problem. Economic fruit production is very difficult in such regions. A severe hailstorm will annihilate any crop. Even light hail can cause blemishes on fruit which destroy their commercial value. Various methods to reduce hail damage have been tried, but nothing short of hail netting, a very expensive option, has proven totally effective.

Geographic Factors

Soils

Good soils have been favoured by horticulturalists, since they make crop production so much easier. However, successful fruit production can occur on poorer soils if enough attention is given to nutrition, organic matter (water-holding capacity), pH adjustment, drainage and irrigation. Skilful growers may even turn an apparent adversity to an advantage by having a greater degree of positive control over some factor affecting growth and fruiting.

Topography

Preferred sites in cool areas are generally those with a gentle slope facing the sun. The slope allows air drainage in...