Comparative Performance of Rice with System of Rice Intensification (SRI) and Conventional Management using Different Plant Spacings

Abstract

The System of Rice Intensification (SRI) reportedly enhances the yields of rice (Oryza sativa L.) through synergy among several agronomic management practices. This study was conducted to investigate the effects on rice plant characteristics and yield by comparing the plants grown with different methods of cultivation – SRI vs. recommended management practices (RMP) focusing on the impact of different plant spacings. Performance of individual hills was significantly improved with wider spacing compared with closer‐spaced hills in terms of root growth and xylem exudation rates, leaf number and leaf sizes, canopy angle, tiller and panicle number, panicle length and grain number per panicle, grain filling and 1000‐grain weight and straw weight, irrespective of whether SRI or RMP was employed. Both sets of practices gave their highest grain yield with the spacing of 20 × 20 cm; however, SRI yielded 40 % more than the recommended practice. At this spacing, canopies also had the highest leaf area index (LAI) and light interception during flowering stage. The lowest yield was recorded at 30 × 30 cm spacing under both the practices, as a result of less plant population (11 m−2), despite improved hill performance. During the ripening stage, hills with wider spacing had larger root dry weight, produced greater xylem exudates, and transported these towards shoot at faster rates. These features contributed to the maintenance of higher chlorophyll levels, enhanced fluorescence and photosynthesis rates of leaves and supported more favourable yield attributes and grain yield in individual hills than in closely‐spaced plants. Moreover, these parameters further improved in SRI, apart from the enhanced percentage of effective tillers and showed substantial and positive impacts on grain yield (17 %) compared with recommended practice. In conclusion, wide spacing beyond optimum plant density, however, does not give higher grain yield on an area basis and for achieving this, a combination of improved hills with optimum plant population must be worked out for SRI.

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

“…Plant spacing affected the yield regardless of cultural practices; i.e., SRI and recommended practice. The highest yield was found at 20 by 20 cm spacing regardless of water management, and the yield of SRI (628 g m À2 ) was higher than that of conventional practice (448 g m À2 ) with 20 by 20 cm plant spacing (Thakur et al 2010a). Lin et al (2005) reported no significant difference in the yield of rice grown under shallow water with wetting and drying (SWD) among plant density of 7.5, 13.5 and 19.5 plants m…”

“…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).…”

“…Nguu and De Datta (1979) reported for conventional rice cultivation that a relatively short-statured variety with moderate tillering capacity must have close spacing for maximum yield; i.e., plant spacing of 15 Â 15 cm gives significantly greater yields than 20 Â 20 and 25 Â 25 cm. Thakur et al (2010a) reported that SRI practices through optimum spacing attempt to minimize competition among rice plants for the various growth factors. Although chlorophyll content of the flag leaves and third leaves decreased with ripening, the rate of decrease is different among planting densities, and chlorophyll content was higher with wider spacing (30 by 30) compared to narrow spacing (20 by 20) (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). These reports indicated that wider spacing was more profitable for producing carbohydrate by rice in the later growth stages of rice plants.…”

“…Laulanié introduced was to move from flooded fields to AWD management, because he realized that the growth of rice was superior in paddy soils that were mostly aerobic (Surridge 2004). There are actually several water management practices that can achieve this objective, i.e., (1) intermittent irrigation before PI, and shallow water management from PI to maturity (Thakur et al 2010a); (2) shallow water depth (10-20 mm) from transplanting to early tillering stage, and 60-80% of the saturated moisture content (SMC) in tillering stage, then shallow water depth (10-30 mm) from elongation to flowering, 80% of SMC during milk ripening stage, and dry field from yellow ripening stage (Lin et al 2005); (3) AWD throughout the crop cycle (Satyanarayana et al 2007); and so on. The main purposes of those variants in water management are water saving and improving root development (Zhang et al 2009).…”