Yoshida - 1981 - Fundamentals of Rice Crop Science

128 FUNDAMENTALS OF RICE CROP SCIENCE
3.7. Nutrient contents of a rice crop (variety IR8) at different stages of growth. IRRI, 1968 dry
season (Yoshida unpublished).
3.4.5. Nutrient uptake at different growth stages
Changes in the nutrient content of the rice plant at different growth stages in both
temperate regions and the tropics have been repeatedly studied. The studies
demonstrate that nutrient uptake is affected by climate, soil properties, amount and
type of fertilizers applied, variety, and method of cultivation (Ishizuka 1965,
1971, Tanaka et al 1964). Nevertheless, thechanges in nutrient content at various
stages in the life history of the rice plant are strikingly similar.
The nitrogen, phosphorus, and sulfur contents in the vegetative parts are
generally high at early growth stages and decline toward maturity (Fig. 3.7). In
contrast, the silicon and boron contents are low at early stages and increase steadily
toward maturity.
The contents of nitrogen and phosphorus are generally higher in the panicles
than in the straw (leaves plus culm), whereas those of potassium, calcium,
magnesium, silicon, manganese, iron, and boron are higher in the straw. Sulfur,
zinc, and copper contents are about the same in both straw and panicle.
3.4.6. Nutrient removal
The total nutrient uptake by a crop is affected by the percentages of nutrients in the
dry matter and the dry-matter production (kg/ha). The total uptake ranges from
30–40 g/ha per crop for copper to 890–1,018 kg/ha per crop for silicon (Table
3.11). Uptake of silicon is far greater than that of any other nutrient. Since the rice
plant absorbs such large quantities of silicon, it is sometimes referred to as a
silicicolous plant.