| Agricultural sciences |
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| Effects of nitrogen management on grain yield and nitrogen use efficiency of two hybrid rice varieties with different panicle masses. |
| Yang Shimin, Yang Zhiyuan, Sun Yongjian, Ma Jun* |
| (Key Laboratory of Crop Physiology, Ecology and Cultivation in Southwest, Ministry of Agriculture/Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, China) |
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Abstract In Sichuan Basin with low solar radiation, the grain yield of hybrid rice was restricted by the high humidity and small diurnal temperature. The breeding and application of large panicle hybrid varieties solved the problem to a certain extent. However, the high-yielding performance of large panicle hybrid rice was not stable. In order to explore the measures of maintaining the high-yielding performance of large panicle hybrid rice, it is necessary to investigate the characters of its grain yield formation. Two hybrid varieties with different panicle masses (Chuannongyou 498, about 5 g per panicle; Chuanyou 6203, about 4 g per panicle) were studied on the differences of dry matter accumulation and yield components, and five different nitrogen (N) managements (the N application proportion of base-tillering and panicle fertilizers was 90∶10, 75∶25, 60∶40, 45∶55, 30∶70, respectively) integrated with 15N tracing were applied to investigate the traits of N uptake across the whole growth stage. The results showed that there was no significant difference in spikelet per panicle between large and medium panicle hybrid rice. Medium panicle hybrid rice showed significant advantages in effective panicles and total spikelet compared to large panicle hybrid rice; however, the thousand-grain mass of large panicle hybrid rice was larger, and this superiority played a major role in gaining higher grain yield than medium panicle hybrid rice. There was no significant difference in dry matter accumulation at maturity stage between large and medium panicle hybrid rice, but difference of dry matter productivity was observed before and after anthesis. Compared to medium panicle hybrid rice, large panicle hybrid rice accumulated more dry matters before anthesis, and larger percentage of which was exported to the panicle at anthesis, contributing approximately 40% of its grain yield. For medium panicle hybrid rice, dry matter exportation only contributed about 25% of its grain yield. For N management treatments, 40% and 25% were the optimal panicle N ratios which could gain the highest grain yields for large and medium panicle hybrid rice respectively. According to the relation formula between panicle N ratio and grain yield, 33% was the optimal panicle N ratio which produced the most grains for large panicle hybrid rice, while the optimal panicle N ratio for medium panicle hybrid rice was 27%. The difference for the optimal panicle N ratio between large and medium panicle hybrid rice was caused by varied demands on N at different growth stages. There was no significant difference for N uptake of basal fertilizer between large and medium panicle hybrid rice. Medium panicle hybrid rice showed significant merits in assimilating N at tillering stage than large panicle hybrid rice. In contrast, large panicle hybrid rice assimilated more N at booting stage. A further increase of panicle N based on the optimal panicle N ratio could increase N recovery efficiency, but N physiological efficiency would drop rapidly and the yield-increasing effects of N fertilizer became poor. In conclusion, 33% and 27% are the optimal panicle N ratios for large and medium panicle hybrid rice, respectively, which increase the grain yield and N utilization efficiency simultaneously.
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Published: 20 November 2015
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氮肥运筹对2个不同穗重型杂交稻产量及氮肥利用的影响
以2个单穗质量差异较大的杂交稻品种川农优498（单穗质量大于5 g）和川优6203（单穗质量4 g左右）为试验材料，通过不同氮肥运筹措施研究两者在日照少、温差小和湿度大的生态条件下产量形成规律，并结合15N示踪技术研究两者的氮素吸收利用特点。结果表明：大穗型和中穗型杂交稻每穗粒数无显著差异，中穗型杂交稻在有效穗数及总颖花量上具有显著优势，大穗型杂交稻则通过更高的千粒质量来实现更高的产量；大穗型和中穗型杂交稻成熟期干物质积累量差异不显著，前者花前干物质积累量大，且其向穗部转运能力更强，弥补了花后光合生产能力较弱的劣势；就氮肥运筹处理而言，大穗型和中穗型杂交稻产量最高处理的穗肥施用比例分别为40%和25%，依据穗肥比例与产量关系曲线，大穗型和中穗型杂交稻最佳的穗肥比例分别为33%和27%。大穗型和中穗型杂交稻不同生育阶段对氮素需求的差异是造成两者最佳穗肥比例不同的重要原因，两者对基肥吸收量无显著差异，但前者对穗肥吸收量更大，而后者对蘖肥积累更多；在最适穗肥比例的基础上继续前氮后移虽然能够提高氮肥回收率，但会引起氮肥生理利用率的迅速降低，使氮肥增产效果变差。
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