Management of rice production systems to increase productivity

the 2002, even though most crop varieties failed completely during this
period. Water is essential for plant growth, its shortage reduces transpiration
due to soil water deficit, which results in reduced photosynthesis, since gas
exchange for both water and CO2 takes place simultaneously through stomata.
Although some drought resistant varieties are known to have a high
photosynthesis:transpiration ratio, it has been proven (Dingkuhn, 1989) that a
strong linkage between water use and plant dry matter production limits
development of varieties that are supposedly drought resistant when water
becomes a significant constraint. Soil water content is the predominant factor
affecting the rate of N uptake. The rate of absorption of nitrate N from the soil
is highly correlated to absorption. Transpiration induces soil solution flow
towards the root surface carrying dissolved solutes with it by convection or
mass flow. A soil profile just before harvesting prevailed that the bulk density
of the test varieties’ roots is concentrated within the 0‐10 cm depth, contrary to
prior hypothesis that they possibly processed a highly diffused root system. It
has also been proven by Mitchell et al. (1998) that genotypes with larger
canopy size tend to be severely affected by early season drought, leaf water
potential decreases rapidly and a large number of young green leaves are lost,
although it may not necessarily reflect on the harvest index (Figure 5).
Harvest Index
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Control Low-Input High Input V. High Input
2002
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