Management of rice production systems to increase productivity

and rewetting of soils as practiced in SRI is comparable to inducing a series of
successive Birch effects during a single cropping season.
Drying and rewetting can also result in increased NO3 uptake by the
rice plant rather than other N forms.
3.1.6. Influence of Repeated Wetting and Drying on Micro‐Nutrient
……..Availability
A flooded rice soil is a complex of an aqueous phase, a solid phase, an
interchangeable gaseous phase, and various flora and fauna. The main
chemical changes brought about by flooding a soil have an impact on
micronutrient supply; the decrease in redox potential due to the depletion of
molecular oxygen leads to reduced Fe and Mn. Submergence for 10 to 12
weeks increases the Fe 2+ and Mn 2+ concentration in the soil solution, regardless
of soil type (Savithri et al., 1999). The concentration of Zn and Cu decreases in
lowland soils, and Zn deficiency is a widespread nutritional disorder of
wetland rice (Neue and Lantin, 1994; Savithri et al., 1999).
3.1.7. Influence of Repeated Wetting and Drying on Methane Gas Emission
Recently the importance of methane as a greenhouse gas has been
recognized and studies have been carried out to assess its contribution to
global warming. About 70% of CH4 production arises from anthropogenic
sources, and agriculture is estimated to be responsible for about two‐third the
anthropogenic sources globally (Minami, 1997). Significant CH4 production
generally occurs only after a field has been flooded for a few days. The major
pathways of CH4 production in flooded soil are the reduction of CO2 with H2,
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