Yield and yield components of rice in major paddy areas in Sabah were studied.
  The yield was mainly dependent on the number of spikelets per unit field area, which depends on the number of panicles per unit field area. On the other hand, the percentage of ripened grains was satisfactorily high in all districts, showing that it would be difficult to further increase it to increase yield.
  The way how to increase the number of spikelets per unit field area differs between improved varieties and local long-term varieties. For the former, it is most important to increase the number of differentiated spikelets per unit field area by increasing the planting density and the rate of application of basal fertilizer. For the latter, it is important not only to increase the number of differentiated spikelets, but also to reduce the number of degenerated spikelets by means of nitrogenous fertilizer application during the period from late spikelet initiation stage to the stage just prior to the reduction division stage of pollen mother cell.
  The percentage of the number of degenerated spikelets to the number of differentiated spikelets shows a high positive correlation to the length of life span of varieties. It implies that the longer the growth duration, the more the spikelet degeneration occurs, due to shortage of nitrogen nutrition. Top dressing of nitrogen is effective in suppressing spikelet degeneration.