Implications of low sowing rate for hybrid rice varieties under dry direct-seeded rice system in Central China

Looming water crisis and labor shortage demand the shift from conventional transplanted rice (CTR) to dry direct seeded rice (DDSR). Hybrid rice varieties possess the potential to grow under DDSR system and can perform well even at low sowing rate. Present study investigated the yield responses of three hybrid rice varieties to different sowing rates and explored the physiological basis for grain yield formation under DDSR system. An inbred rice variety was grown as control. Results showed that reducing sowing rates of hybrid rice varieties from 240 seeds m−2 to 60 seeds m−2 did not reduce grain yield, while that of inbred rice varieties declined with decreasing sowing rates. Decreased sowing rates of inbred rice varieties recorded insufficient tillers, and lower panicle number that decreased their yield. Contrarily, for hybrid rice varieties grain yield was maintained even at reduced sowing rate because of their enhanced tillering capacity, higher specific leaf weight (SLW), and increased spikelet number per panicle (SPP), which might have compensated the reduced sowing rate. Our results suggested that the sowing rate of hybrid rice varieties can be reduced to 60 seeds m−2 without compensating yield of DDSR. However, adversities of low sowing rate in DDSR like weeds and poor stand establishment should be overcome to achieve maximum crop yield.