Direct seeding flooded rice: a challenge to agronomists and breeders
1989
Javellana, C.B. | Dingkuhn, M. | Schnier, F. | De Datta, S.K. | Pamplona, R. | Marqueses, E. | Faronilo, J. (International Rice Research Inst., Los Banos, Laguna (Philippines). Agronomy Dept.)
Direct seeding has become an increasingly popular alternative to transplanting in tropical flooded rice culture due to increasing labor costs, the availability of herbicides and fast emerging, early maturing, N-responsive rices. However, agronomic research and breeding have been largely focused on transplanted rice (TPR) culture while specific cultural and genotypic requirements of direct seeded flooded rice (DSR) are not well documented. Callaborative research of IRRI [International Rice Research Inst., Los Banos, Laguna, Philippines] and West German Universities sought to fill this knowledge gap. Patterns of tillering, foliage expansion, nitrogen economy, canopy CO2 assimilation (Ae) and respiration, and yield were studied in DSR and IR64. Modelling aided growth analysis and conceptual extrapolation of the results. The data indicated close relationships TPR between foliar N concentration, leaf area index (LAI), Ae and yield. All growth processes were delayed by transplanting shock. Direct seeded rice developed higher LAI, tiller number and vegetative growth than did transplanted rice, but growth efficiency was lower due to dilution of N in the tissues. Foliage overgrowth reduced yield. The authors conclude that direct seeded flooded rice culture requires a modified plant type with lower tillering ability, lower LAI during reproductive growth stages, higher N concentration in the foliage and an expanded assimilate storage capacity of the stems. Yield of this plant type maybe 10 to 30% higher than that of current cultivars, depending on nitrogen fertilization.
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