Management of rice production systems to increase productivity

low‐input varieties were also found to have higher NUE than the Asian
variety (Peking). In lowland rice farming, water control is the most important
management practice that determines the efficacy of other production inputs.
Poor drainage that keeps soil saturated is detrimental to crops and degrades
soil quality. In many rice irrigation systems in The Gambia, water control is
highly inefficient. Drainage mechanisms are dysfunctional or inadequate
because farmers believe that rice grows best when water is supplied in
abundance. Poor drainage mechanisms makes it necessary for farmers to
transplant tall, very old seedlings, usually 4 ‐ 6 weeks old, and 3 – 4 seedlings
per hill. Rice fields are kept continuously flooded and are flood‐free only at
time of harvest. This practice is not only wasteful in terms of water use
efficiency, but also leads to leaching of soluble nutrients, blocks aerobic soil
microbial activities and biological nitrogen fixation as well as slows
mineralization and nutrient release from the soil complexes. New
management practices that address lowland rice production constraints in The
Gambia are needed. The System of Rice Intensification (SRI), used in
Madagascar, proposes a methodology that has the potential to increase rice
productivity without a high investment in external inputs or introduction of
new cultivars. SRI changes the ways in which plant, soil, water and nutrients
are managed. In 2000, 2001, and 2002, SRI experiments were conducted in The
Gambia. The SRI water management practices of repeated soil wetting and
drying were found to be beneficial to rice plant growth probably through
increased biological nitrogen fixation, more nutrient availability, profuse root
development, increased tillering, and a high panicle setting ratio leading to
higher grain yields. Grain yields of rice under SRI management are 2‐3 times
higher than the national average in The Gambia.
iv