The effect of nutrient and water management on irrigated rice cultivation.
Paddy rice (Oryza sativa L.) was grown as three successive
annual crops (dry season of November February, early wet season
of March June, and late wet season of July September). During
the last part of the wet season, prior to the dry season, all field
plots were flooded by adjacent river water for 1.5-2 months
(September November). The soil underwent rotary tillage once
every year, before the early wet season, to a depth of 7-10 cm and
there was a hardpan at ca. 15 cm depth. Extension of rice roots
below this depth was very limited.