Effects of Plant Density and Nitrogen Application Rate on Grain Yield and Nitrogen Uptake of Super Hybrid Rice

Towards an understanding of the high productivity of rice with System of Rice Intensification (SRI) management from the perspectives of soil and plant physiological processes

“…Leaf area index (LAI) of rice plants planted at 13.5 plants m À2 was the highest among other plant densities evaluated (7.5 or 19.5 plants m À2 ) at 20 days after heading (Lin et al 2005). Although the largest leaf area per hill was found with wide plant spacing (30 by 30 cm) at flowering (Thakur et al 2010a), medium plant spacing (20 by 20 cm) recorded the highest LAI among treatments at 20 days after heading (Lin et al 2009;Thakur et al 2010a). The wider spacing between plants under SRI management leads to a more prolonged, open crop canopy (Stoop 2005).…”

“…This high chlorophyll content with wider spacing was attributed to higher root-oxidizing activity of more widely-spaced rice plants (Mishra and Salokhe 2010). The SPAD value of the flag leaf of hybrid rice with lower plant density grown under SRI management was higher than with higher plant density at the flowering stage (Lin et al 2009). Plants grown under wider spacing had a higher photosynthetic rate in their leaves than did those with closer spacing regardless of water management during the ripening stage of the rice plants (Thakur et al 2010a).…”

“…Few reports were available about the effect of N application rate on the growth and yield of rice under SRI (Lin et al 2009;Zhao et al 2009), because N fertilizer was not widely referred to SRI practices (Thakur et al 2010b) and more organic matter was commonly applied to SRI fields than to conventional practice fields (e.g., Tsujimoto et al 2009). The application of N at the rate of greater than 180 kg ha À1 (which included compost as an N source) recorded a maximum yield of 9.5 t ha À1 for hybrid rice grown under SRI, while the yield of hybrid rice grown conventionally with the same N dose by chemical N fertilizer, was 7.7 t ha À1 and yield increased with more N (Lin et al 2009).…”

“…The application of N at the rate of greater than 180 kg ha À1 (which included compost as an N source) recorded a maximum yield of 9.5 t ha À1 for hybrid rice grown under SRI, while the yield of hybrid rice grown conventionally with the same N dose by chemical N fertilizer, was 7.7 t ha À1 and yield increased with more N (Lin et al 2009). Optimum application rate of fertilizer N should be investigated under SRI management condition with inbred rice.…”

“…The relationship between amounts of N in rice plants at harvest and grain yields is shown in Fig. 2 (data from Lin et al 2009). There was a linear relationship between the two parameters, regardless of whether SRI or conventional practices were used, in the various plant density levels.…”