Agriculture Reference
In-Depth Information
Figure
8.13.
Rainfall (RF) verses evapotranspiration (ET) for a wet climate; D represents times
of water deficit.
if water for irrigation is available. This method thus gives a ready, visual, method of
determining the availability of water for crop production.
Figure 8.12 is an example of a dry or desert-type climate. There is a deficit in soil
water throughout most of the year. Excess moisture at some times is not enough for
crop production during the remainder of the year. Under these conditions there is insuffi-
cient water for recharge of groundwater, and irrigation from groundwater is not advisable
because it will not be sustainable.
Figure 8.13 is an example of a wet climate, where there is a deficit during short
periods that is more than made up for the rest of the year. Soil storage of moisture is
sufficient to provide water for crops during this time. Excess water during the remainder
of the year either runs off into streams and rivers or percolates into groundwater. Under
these conditions excess water can then be safely used for irrigation (Chapter 9
for further information about irrigation).
Note that this method gives great emphasis on rainfall and evaporation. However,
other climatic factors needed for crop production, that is, temperature, day length, and
the like must also be appropriate for the crop to be grown.
8.4
CROP PRODUCTION AND CLIMATE
People live and raise both crops and animals in almost all climatic zones, exceptions
being very high mountains, the permanently frozen parts of both the north and south
polar regions, and those very dry regions without sources of water for drinking and irri-
gation. Different climatic conditions usually mean that crops and animals adapted to
that climate are grown and raised. There are several exceptions to this. One is that
plant and animal breeders are constantly breeding new varieties of crops and animals
adapted to areas where they are not naturally grown or raised. Second, maize is
