Comparison of the effect of fertilizer application at and after the stage of panicle-base initiation on yield and yield components of semi-dwarf and standard rice cultivars

Abstract

Rice responds to fertilizer application at the panicle-base initiation stage. A high fertilizer application at this stage increases the number of spikelets, especially the number of spikelets on the secondary rachis branches which are inferior in grain-filling, and deteriorates the canopy architecture through the elongation of leaf blades which are alive during the grain-filling period. The increase of the number of spikelets results in the reduction of the ripening percentage; hence, yield decreases. The present study was undertaken to analyse the response of four cultivars harbouring the semi-dwarf gene (d-49) and two standard cultivars to fertilizer application at and after the panicle-base initiation stage. Three levels of nitrogen fertilizer, i.e. 96, 230 and 420 kg/ha, were applied as split applications. The increase of fertilizer level increased number of spikelets per panicle and reduced ripening percentage in all cultivars. However, the decrease of ripening percentage was not very pronounced in some of the semi-dwarf cultivars when compared to the standard tall cultivars. This may be due to the fact that upright culms in the semi-dwarf cultivars with decreased internodes afforded a good canopy architecture, i.e. a well-balanced arrangement of leaf blades, and hence increased assimilate supply to the grains.