Upland rice—900 mm minimum during the growth period, or many light
(^3) /ha.
For both types of rice the two most critical periods for water supply are 10–12 days
before tillering, and during flowering.
Altitude: the terms “upland” and “lowland” rice are misleading. Very often the so-
called upland varieties are grown at much lower altitudes than lowland varieties, and
vice versa.
Diseases: Leaf Blight and Leaf Streak are caused by bacteria. At least 11 fungi also
attack rice, of which five are described below:
–Blast. The most widespread and devastating. Plants can be attacked by this fungus
at all stages. Small blue flecks appear on the leaves, which become brown with grey
centres; these spread until the whole leaf becomes brown. If the attack is early, the
grains do not fill and the panicle falls over, hence the other name for this disease
“rotten neck”. Control is by resistant varieties and use of clean seed; copper
fungicides and seed dressings may also help to some extent.
- Brown Spot. Damage occurs both in nurseries and fields, especially in cold
weather. Control is by seed dressings and burning the stubble of infected crops. - Narrow Brown Leaf Spot. Foliage dies off early. Controlled with resistant
varieties. - Gigantism (Foot Rot or Bakanae Disease). Caused by a Gibberella fungus.
Common in Asia, especially in seedbeds. Plants become very tall and thin, with few
tillers; the panicle emerges poorly, and the grain is shrivelled. Occurs in wet soils
above about 20C. Control is by seed dressings and destruction of diseased
seedlings. - Stem Rot (Sclerotial Disease). Excessive late tillers, and loss of grain. Normally
only occurs when plants are in unfavourable conditions. Control is by burning
infected stubble and by taking care with the irrigation water, which spreads the
disease.
There are also nine Virus Diseases, including Hoja Blanca, Yellow Dwarf, Orange
Dwarf, Dwarf, Tungro and Grassy Stunt.
Pests: extensive damage is frequent, both in fields and stores. The worst of the field
pests are stem borers, leaf miners, armyworms, grasshoppers, locusts and various
nematodes. Rice is also damaged by rats, crabs and birds. Storage pests include Rice
Weevil, Lesser Grain-borer, Khapra Beetle, Saw-toothed Grain Beetle and the
Angoumois Grain Moth.
YIELD
According to FAO, the global average for 1988/90 was 0.9–6.6 MT/ha for the
bottom 10% and top 10% of countries respectively, being higher in Asia and lower
in South America and Africa. The global average figure for paddy rice in 2004 was
4.0 MT/ha, ranging from 9.69 MT/ha in Egypt to 750 kg/ha in the Congo.
The International Rice Research Institute (IRRI) in the Philippines and other
plant breeders have increased rice yields by two or three times since the 1960s.
Modern hybrids and open pollinated varieties can yield around 10 MT/ha in ideal
conditions.
the water level is slowly increased to 15–30 cm as the plants grow, then decreased
at flowering until almost dry at harvest.
Paddy rice—transplanted into a well-soaked field, with some standing water;irrigations, 10–15 or more, to provide a total of between 400 and 600 m