Effects of Sowing Date and Sowing Amount on Yield Formation Characteristics of Direct-seeded Rice in Southern Henan

To investigate the effects of sowing date and sowing amount on the yield and dry matter accumulation of direct-seeded rice in southern Henan, five sowing date treatments, namely A₁ (25 April), A₂ (5 May), A₃ (15 May), A₄ (25 May), and A₅(4 June), and five sowing rate treatments, namely B₁ (18.0 kg/hm²), B₂ (22.5 kg/hm²), B₃ (27.0 kg/hm²), B₄ (31.5 kg/hm²) and B₅ (36.0 kg/hm²), are set up using the rice variety Fengyouxiangzhan as the experimental materials. The results show that the effects of both sowing date and sowing amount on yield reaches a very significant level, and the effects of their interaction on yield, effective panicle number, grain number per panicle and 1000-grain weight are highly significant. With the delay of sowing date, the yield of direct-seeded rice increases first and then decreases. Under the sowing dates of A₁, A₂, A₃, A₄ and A₅, the maximum yields of direct-seeded rice under A₁B₅, A₂B₃, A₃B₃, A₄B₄ and A₅B₅ treatments are 7 531.7, 9 169.5, 9 470.3, 7 961.9 and 7 462.9 kg/hm², respectively. Direct-seeded rice achieves the highest yields at the A₃B₃ level with a suitable effective panicle number, more grains per panicle, more dry matter accumulation and higher dry matter accumulation rate at the late growth stages.