麦秸还田与氮肥互作对大穗型杂交粳稻不同部位枝梗和颖花形成的影响

【目的】探讨麦秸还田和施氮量对大穗型杂交粳稻不同部位枝梗和颖花形成的影响。【方法】以大穗型杂交粳稻甬优1540为试验材料，设置麦秸还田（T0：麦秸不还田；T1：麦秸全量还田）和施氮量（N1：施纯氮225 kg·hm^-2；N2：施纯氮300 kg·hm^-2；N3：施纯氮375 kg·hm^-2）二因素试验，裂区设计，秸秆处理为主区，研究稻穗不同部位枝梗与颖花形成规律。【结果】麦秸还田提高大穗型杂交粳稻籽粒产量，但不显著；不同施氮量处理对产量的影响显著，表现为N2＞N3＞N1。大穗型杂交粳稻不同部位枝梗与颖花形成特性因着生部位不同而异。麦秸还田与施氮量对枝梗与颖花形成有显著影响，与T0相比，T1处理显著降低了总枝梗与颖花分化数，但同时显著减少了退化数，且退化数的降幅大于分化数，导致现存数比T0显著增加；麦秸还田对一次枝梗的形成影响不显著，但显著影响了二次枝梗与颖花的形成。3种氮肥水平下，N2处理的总枝梗数、颖花分化数和现存数最高，而退化数率最低，且对一、二次枝梗与颖花的影响均达显著水平。麦秸还田与施氮量存在互作效应，T0N2处理下枝梗和颖花的分化数最高，但T1N2处理下的枝梗和颖花的退化数显著低于其他处理，现存数最高；麦秸还田和不同施氮量处理对上部一、二次枝梗与颖花的影响均不显著，但显著影响了中、下部枝梗与颖花形成，特别是下部二次颖花的分化与退化对总颖花数的形成有较大影响。枝梗及颖花性状与产量关系密切，一、二次枝梗与颖花现存数与产量及每穗总粒数均达极显著正相关; 枝梗与颖花的分化数和现存数与有效穗数和结实率均呈一定的负相关关系，但与千粒重呈显著或极显著正相关。【结论】大穗型杂交粳稻稻穗不同部位枝梗和颖花形成规律有差异；麦秸还田和施氮量对枝梗和颖花形成有显著影响，影响程度因稻穗部位不同而异，中下部和二次枝梗受影响较大；秸秆还田和施氮量存在互作效应，麦秸全量还田和适宜的氮肥水平有利于枝梗和颖花的形成。

Effects of Interaction of Wheat Straw Residue with Field and Nitrogen Applications on Branches and Spikelets Formation at Different Positions in Large Panicle Hybrid Rice

【Objective】The objective of the study is to investigate the effect of wheat straw-residue with field and nitrogen applications on the formation of branches and spikelets of hybrid japonica rice with large panicle.【Method】 A field experiment was conducted with the two applications of wheat straw to field (no wheat straw residue applied to field, T0; all wheat straw residue applied to field, T1) and three nitrogen (N) rates ( 225 kg·hm^-2, N1; 300 kg·hm^-2 , N2; 375 kg·hm^-2 , N3) by using the hybrid japonica rice cultivar, Yongyou 1540 as material. 【Result】 All wheat straw residues applied to field could increase the yield, but not significantly.N rates significantly influenced the yield, and at the N rate of 300 kg·hm^-2 the yield was significantly higher than at the N rate of 225 and 375 kg·hm^-2. The branch and spikelet formation of large panicle hybrid rice varied with their position at a whole rice panicle. The wheat straw and N rates significantly influenced the formation of the branches and spikelets. Compared with T0, the number of differentiated and retrograded total branches and spikelets were all significantly decreased under T1, and the retrograded number decreased more than the differentiated, resulting in the survived number being higher than those under T0. The wheat straw did not significantly affect the formation of the primary branches, but significantly affected the formation of the secondary branches and spikelets. N rates significantly affected the primary and secondary branches and spikelets. The number of differentiated and survived total branches and spikelets at the N rate of 300 kg·hm^-2 were highest among three N rates, while the retrograded number and percentage were lowest. Under the treatment of T0N2, the number of differentiated branches and spikelets were highest, but the number of retrograded branches and spikelets under T1N2 treatment were significantly higher than other treatments, which indicated that the survived number were highest. The wheat straw and N rates did not significantly affect the primary and secondary branches and spikelets at the upper part of a panicle, but significantly affected the formation of the branches and spikelets at the middle and basal part. It is worth noting that the differentiation and degradation of secondary spikelets at the basal part greatly affected the formation of the total spikelets. The survived primary or secondary branches and spikelets were significantly positively correlated with the yield and grain number per panicle. The differentiated and survived branches and spikelets were negatively correlated with the productive panicle number and seed setting rate, but significantly positively correlated with1 000- grain weight.【Conclusion】There was a difference on the formation rules of branches and spikelets at the different parts of a panicle of the hybrid japonica rice with large panicle. The wheat straw and N rates significantly affected the formation of the branches and spikelets, especially the secondary branches and spikelets at the middle and basal part. The interaction effects existed between the wheat straw-residue applied to field and N rates. All wheat straw-residues applied to field and optimum nitrogen rates were conducive to the formation of branches and spikelets.