A manual of rice seed health testing - IRRI books - International Rice ...

–The rainfed, medium-deep, waterlogged
environment experiences
waterlogging, with water depths
ranging from 25 to 50 cm in bunded
or unbunded fields.
The deepwater environment has
unbunded fields with 0.5-3 m of
standing water. It has two
subcategories.
–The deepwater environment has
50-100 cm of water.
–The very deepwater environment
has water depth exceeding 100
cm.
The upland environment has
bunded or unbunded rainfed fields
with no surface or rhizosphere water
accumulation. Hydromorphic
ricelands in West Africa are examples
of this ecosystem. Varieties
suited for this environment should
have deep root systems, be able to
recover from drought, withstand
aluminum toxicity and iron deficiency,
and be resistant to blast. It
has four subcategories.
–The favorable upland environment
with long growing season has a
long rainy season and highly fertile
soil with good water-holding capacity.
–The favorable upland environment
with short growing season has
a short rainy period and favorable
growing conditions, but drought is a
major constraint.
–The unfavorable upland environment
with long growing season
has a long rainy season but
unfavorable soil or topographic factors.
–The unfavorable upland environment
with short growing season
has a short rainy season and poor
soil conditions.
Tidal wetlands are near the seacoasts
and inland estuaries and are
influenced by tides. This heterogeneous
environment has four subdivisions.
–Tidal wetlands with perennially
fresh water are away from the
sea and do not have saline water.
–Tidal wetlands with seasonally
or perennially saline water are
found near seacoasts and at estuary
mouths.
–Tidal wetlands with acid
sulfate soils occur near coasts and
inland estuaries, are affected by salt
water, and are not planted to rice.
–Tidal wetlands with peat soils
exist near seacoasts and estuaries.
Not currently in use for rice production,
these areas could be utilized for
growing rice.
Rice plant and its environment 9