Agriculture Reference
In-Depth Information
boundary of Köppen recognizes the dramatic slowing of tropical plant growth
and development at lower temperature. At temperatures less than 10-12°C
and above freezing, most plants that evolved in the tropics stop growing and
are injured, depending upon length of exposure and species; this response
is called chilling injury. Precipitation and evaporation signifi cantly impact
natural vegetation and subsistence agriculture, although irrigation does allow
horticultural production to proceed.
Several major tropical climatic types have been described:
1.
Wet tropics
: The wet equatorial or humid tropics, equatorial zone or tropical
rainforest occurs within 5-10° of the equator. It is characterized by constantly
high rainfall, humidity and heat. Rainfall is well distributed and may range
from 2000 to 5000 mm or more annually. Solar radiation is reduced due to
cloudiness. Vegetation is luxuriant on very weathered soils. Undisturbed, the
soil supports natural vegetation very well, but under cultivation the soils lose
their organic matter and porosity rapidly. Much of the land in the wet tropics
is undeveloped and in some areas unpopulated. Attempts have been made to
improve productivity, but past attempts by private industries and government
agencies have often not succeeded.
This wet tropics climatic type is common in parts of Africa within the 10°
N and S latitudes and includes the Congo Basin, Gulf of Guinea in West Africa,
parts of Kenya and Tanzania in East Africa; in South America the Amazon
Basin of Brazil and countries bordering the basin, such as French Guiana,
Guyana, Surinam and Venezuela; and in South-east Asia most of Malaysia,
Indonesia, Papua New Guinea, the Philippines and some Pacifi c islands.
The wet tropics are not limited to the above areas and are also widespread in
countries bordering the equator.
2.
Wet and dry tropics
: This is also known as the monsoon rainforest, with
marked seasonal rainfall between 5
and 15° N and S of the equator and as far
north as 25° in parts of tropical Asia (Fig. 2.2). Walter (1973) extended this
zone from about 10°
N and S to about 30° N and S latitudes. Maximum rainfall
occurs in the summer when the sun is directly overhead, with the dry season
in the cooler months. A tropical fruit horticulturist will probably spend most of
their time in this climatic zone.
This wet and dry tropical climate is found in a wide region of Africa, Asia,
the Americas, Australia and the Pacifi c tropics. Many tropical fruit species are
well adapted to wet-dry climatic conditions. For fruit production, some form
of irrigation is necessary, especially in areas where the wet season is relatively
short. A dry period in winter may substitute for cool temperatures in crops
requiring some stress prior to fl owering. However, irrigation is desirable once
fl owering begins and during fruit development.
3.
Dry tropics
: Also called the tropical savannah, occurs to the north and
south of the monsoon climate zone along the Tropics of Cancer and Capricorn,
between 15°
and 20°
N and S latitudes. It is characterized by hot, dry desert
