Agriculture Reference
In-Depth Information
sulfate soils require specialized management strategies, such as raised beds, to
be productive.
A prime soil requirement for all crops is good drainage to prevent
waterlogging, which leads to root diseases. Drainage is crucial for crops that
are susceptible to
Phytophthora
root rot, such as avocado, papaya, passion
fruit and pineapple. Mango and avocado have been observed to show branch
dieback in parts of fi elds in western Mexico with a water table around 50-60
cm below the soil surface.
CLIMATE CHANGE
Climate change is regarded as the most important threat facing the environ-
ment that will have a signifi cant ef ect on society and agriculture. For the
tropics, climate change is predicted to expand the tropical region, with
signifi cant changes in temperature (2-5°C increase) and rainfall (more
variable). The predictions are made for large regions and the expectation is
that there will be less rainfall near the equator and more rainfall, with greater
variability, further away from the equator, in the current drier tropical zones
(Easterling and Apps, 2005; Cerri
et al.
, 2007; Ingram
et al.
, 2008).
The predicted direct environmental changes include freshwater avail-
ability, carbon and nitrogen cycling, land cover and soils. All these changes
will directly impact biodiversity and agricultural, including horticultural,
productivity. It is expected that the induced biodiversity changes will lead to
new pest and disease pressures and greater weed problems (Sutherst
et al.
,
2007). For example, aphids are expected to become an increasing pest because
of their low development temperature threshold, short generation time and
high dispersal ability. Pathogens may have higher growth rates and more
generations per growth season. Weeds, with their more rapid growth and
development, may be more favoured in comparison to crops.
SUMMARY
Whereas temperature is the major limitation to plant growth in temperate
areas, in the tropics rainfall plays that role. There is considerable variation
in tropical climates due to altitude, continentality and the presence of large
bodies of water. Disease and insect problems are more severe in high-rainfall
areas. Year-round plant growth is generally only limited in the tropics by
moisture availability. Good soils are available in the tropics, and the high
value of horticultural crops means that they can command the use of more
favoured areas.
