Growing Food: A Guide to Food Production

(Elle) #1
Maize and cowpeas—wheat should do well.
Cotton—wheat performs somewhere between the two above.
Green manure—wheat yields about the same as after a fallow, and green manuring
is not worthwhile in areas with less than about 375 mm rainfall a year.
Sesame and cucurbits—wheat should yield well.
Sorghum and barley—wheat will not normally flourish.
Pulses and oilseeds—wheat will also often not flourish.
In low technology farming systems, wheat should not be grown consecutively on the
same land for more than 3 or 4 years, or even less.

GROWTH CONDITIONS
Day length: most wheat species are long-day plants.
Growth period: anywhere between about 95 and 150 days, with a rough average of
130 days. The growth period is extended by about 15 days for every 300 metres
increase in altitude. Sometimes it is possible to grow two wheat crops per year, but
this is dangerous and can lead to a buildup of Rust and other diseases.

At the other extreme, some winter wheats grow in some of the coldest regions.
High temperature may result in low yields of small grain, especially if there are also
hot dry winds.
Rainfall: wheat is generally less tolerant of drought or irregular rainfall than barley,
but can sometimes produce some crop with only 200–500 mm during its growth
period. Most of the important wheat regions of the world have less than 700 mm a
year. In the tropics, irrigation is usually necessary if there is less than 200 mm
rainfall during the growth period.
Altitude: wheat is grown from sea level to about 3500 m above sea level. In the
tropics it is normally grown between 1600 and 3500 m. In Ethiopia, mainly 1800–
2500 m. Many tropical countries attempt to grow more wheat at high altitudes so as
to reduce food imports. At lower altitudes in the tropics there is often too little
rainfall, or it is too hot and humid, which increases the damage caused by diseases.
Pests:

(larvae) are slender, glossy and pale green; they may kill one or more tillers of
young plants. In older plants, the grain is shrivelled and the plants may die
prematurely.


  • Aphids—normally attack in the early growth stages and during droughts. Wheat
    aphids and the so-called Greenbug damage plants by sucking their sap and, more
    seriously, by transmitting virus diseases. Can be controlled with insecticides such as
    Parathion.

  • Wheat Stem Maggot—mainly in Asia, Europe and America. The maggots


146 TONY WINCH



  • Wireworms—these larvae are slender, hard, shiny and slow moving, with 3 pairs
    of short legs. They attack germinating grain and also roots and stem below ground,
    which usually causes death of the plant. Lindane soil treatment is possible but very
    expensive.


Temperature: the minimum for growth is about 3–4°C, and the optimum is
25–27°C. Varieties have been developed to grow well in a wide range of
temperatures. Wheat can grow in very high temperatures, above 40°C, provided that
the air humidity is not too high.

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