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Influence of Seedling Age at Transplanting on Rice Performance¹

With the advent of high-yielding rice (Oryza sativa L.) varieties on the cost of Peru, the question arose as to how these short-statured plant types react to delays in transplanting, a common situation in the field because of uncertain water supply. A field experiment conducted in Lambayeque, Peru evaluated two short-statured varieties, ‘IR8’ and ‘IR5,’ with the tall, traditional ‘Minabir’ variety at transplanting dates from 30 to 105 days after seeding and at three seedbed growth rates. IR8 produced the highest grain yield (12.0 tons/ha) when transplanted at 30 days after seeding. Yields decreased linearly at the rate of 125 kg/ha per day of delayed transplanting beyond 30 days. Minabir showed less-pronounced yield decreases up to 75 days after seeding. Slowing seedbed growth of IR8 through water and N stress produced significant yield increases when transplanted at 75 and 90 days after seeding. Delayed transplanting reduced plant height and dry matter production, caused flowering shortly after transplanting in some cases, and decreased panicle production and the number of fertile grains per panicle. Seeding density had no effect on yields. The experiment showed that the short-statured plant types are more sensitive to delays in transplanting than the tall ones, but that the new varieties can outyield the tall varieties when transplanted up to 90 days after seeding.

Key Words: Plant types • Physiological disturbances • Seedbed management • Seedling density • Variety-cultural practice interactions • Yield components • Panicle abortion

² Assistant Professor of Soil Science and Coleader National Rice Program of Peru, North Carolina State University, Raleigh.

³ Assistant Agronomist, National Rice Program, Centre Regional de Investigaciones Agropecuarias del Norte, Ministerio de Agricultura, Zona Agraria II, Lambayeque, Peru.

Received for publication February 25, 1972.