Effect of Transplanting Density on Yield Formation of Different Panicle-typed Varieties in Ratooning Rice Production

【Objective】 Transplant is a cultivation commonly used in ratooning rice production in southern China and other eastern Asian countries. Its impact on rice growth and yield depends on a range of factors. This paper presents an experimental study of the effect of transplanting density on yield composition of different panicle-typed varieties. 【Method】 The field experiment compared three rice varieties: Tianyou Huazhan, Huiliangyou 898 and Yliangyou 900. The transplanting density treatments for all three varieties were the same: 1.5×104 points/hm2 (D1), 187 500 points/hm2 (D2), 225 000 points/hm2 (D3), 262 500 points/hm2 (D4), 300 000 points/hm2 (D5), and 337 500 points/hm2 (D6). In the experiment, we measured rice growth and its ultimate yield formation in each treatment. 【Result】 Transplanting density affected composition of both seasonal and annual rice yields significantly, but the effect varied with rice varieties. There was a lack of variety-planting density interaction on the yield. The variety Huiliangyou 898 had the highest seasonal and annual yields, strong coordination ability among yield factors, high seed setting rate; variety Tianyou Huazhan had strong tillering ability, high ear-setting rate and full panicle numbers per unit area. All these were significantly higher than those of the variety YLY900. The variety YLY900 had fast population growth rate and high grain numbers per panicle, but its tillering ability was poor, and ear-setting rate and low harvest index were low; it hence produced the lowest seasonal and annual yields. On average, the optimal transplanting density for the three varieties was D5, producing highest seasonal and annual yields, faster tillering rate and more tillers per unit area; it also significantly increased the panicle numbers and sink capacity, population growth rate, and dry matter accumulation. 【Conclusion】 Selecting rice varieties with panicle and grain for the initial season in ratooning rice production should consider its tillering ability to achieve high yield. For the three rice varieties we compared, the optimal transplanting density is 300 000 holes/hm2.