Maclean et al. - 2002 - Rice almanac source book for the most important e

and high levels of exchangeable Al. Upland rice
soils in most of Africa have low available WHC
because of coarse texture, are often kaolinitic
(i.e., low-activity clay soil with low CEC), and
have severe nutrient deficiencies and Al and Mn
toxicities.
Dry soil preparation and direct seeding in
fields that are generally unbunded are common
in upland rice culture. Surface water does not
accumulate for any significant time during the
growing season. In some countries such as in
eastern India and Bangladesh, upland rice fields
are frequently bunded to save scarce water.
Upland rice and food security
Upland rice is primarily grown as a subsistence
crop. It is critical to the food security of
impoverished communities that do not produce
enough lowland rice to meet their needs. In
eastern India and Bangladesh, upland rice is
grown by farmers who also have lowland fields,
but who face a “hungry month” before lowland
crops can be harvested; the upland crop, which is
harvested early, bridges the family through a
period when food is extremely scarce. In other
areas such as the mountains of northern Lao
PDR, many farm families have no lowland
holdings and are heavily dependent on upland
rice for subsistence. A commercial cropping
system with an upland rice component has
emerged only in the Brazilian Cerrado region
and in northern China (see below).
In Côte d’Ivoire, Guinea, Guinea Bissau,
and Sierra Leone, upland rice is the only staple
available between the maize and cassava
harvests, or between sweet potato and cassava.
Recently, interspecific hybrid rice (or NERICA)
has been the main food available in the “hunger
period” from late September to late November
(see page 36).
Predominant cropping systems
Depending on the size of their farms and their
resources, upland rice farmers use farming
systems ranging from shifting to permanent
cultivation. Shifting cultivation is common in
Indonesia, Lao PDR, northern Thailand, and
Vietnam in Asia, and in the forested areas of
Latin America and West Africa. Farmers plant a
rice crop alone or in association with other crops
such as maize, yam, beans, cassava, or plantains.
In many places, including Indonesia, the
Philippines, Southwest China, and Brazil, upland
rice may be intercropped with maize. In areas
with sufficient rainfall, upland rice may be
followed by a crop of maize, cowpea, beans,
soybean, or sweet potato. In West Africa, one or
more crops may be mixed with upland rice.
Farmers use an area for 1–3 yr until soil fertility
declines and weed and pest infestations increase.
They then abandon the land and return to
previously abandoned farmland or start cropping
on other available fallow land. In traditional
shifting cultivation systems, fallow periods were
as long as 30 years. This lengthy fallow restored
fertility and prevented weed seed buildup. Now,
rotations in most upland areas practicing shifting
cultivation have shortened to a 2- or 3-yr cycle
because of increased population pressure. This
has resulted in increased weed pressure and
reduced soil fertility.
One variation of shifting rice cultivation is
pioneer cultivation where fallow is replaced by
perennial vegetation such as pasture or trees.
Rice is intercropped with young fruit and forest
trees for 2–3 yr (intercalary cultivation). As the
trees grow, they shade more area and less rice is
planted. After a few years, the rice crop is
transferred to a new area. Pioneer cultivation is
common in Brazil, but rare in Asia and Africa,
although it is becoming popular in Indonesia
under rubber, oil palm, and teak.
Permanent cultivation of upland rice is
practiced in many Asian and Latin American
countries. This is characterized by orderly intercropping,
relay cropping, and sequential
cropping with several crops. The largest area of
permanent upland rice cultivation is in eastern
India. In the Chhattisgarh Plateau area of
Jharkand and Bihar, rainfall will support only a
single upland crop per season. Rice may be
grown continuously or rotated with legumes and
pasture. Rice yields in continuous production
tend to be very low (around 1 t/ha) because of
nematode buildup and other biotic factors that
are not well understood, but yields in rotation
with legumes may exceed 2 t/ha. In eastern Uttar
Pradesh, upland rice is usually double-cropped
with gram, mustard, or other upland crops.
Because the risk of crop damage or loss resulting
from drought or pests is high, and because
upland rice farmers are usually poor and have
limited access to credit, most apply few inputs of
animal manure, organic matter, chemical
fertilizer, and pesticide to upland rice crops. This
is particularly true in areas where farmers
The rice plant and its ecology 21