双季晚粳稻氮肥精确运筹研究

【目的】我国南方双季稻区晚稻品种以籼稻为主。近年来我国粳米需求量逐渐增大，研究者提出了利用南方双季稻区充足的温光等资源进行晚季稻籼改粳以提高粳稻总产量。系统研究双季晚粳稻高产、优质和高效的氮肥运筹方式就显得十分重要。【方法】 2011~2012年，在南方典型双季稻区江西省上高县泗溪镇，以杂交粳稻常优5号和甬优8号为晚稻材料，在总施纯氮量 225 kg/hm2 条件下，设置10∶0、8∶2、7∶3、6∶4、5∶5、4∶6、3∶7 七种基蘖肥与穗肥运筹比例，通过研究不同氮肥运筹方式对双季晚粳稻产量及其构成因素、叶面积指数、茎蘖动态、光合物质生产与积累、氮 素吸收利用以及稻米品质等方面的影响，明确了南方稻区双季晚粳稻氮肥精确运筹模式。【结果】 随基蘖肥占总施氮量比例的降低，结实率、千粒重和每穗粒数呈先增加后减少的趋势，穗数呈减少趋势。氮肥基蘖肥与穗肥比例在6∶4、7∶3范围内，双季晚粳稻群体穗数充足、穗型大、群体颖花量高，且结实率和千粒重较稳定，产量显著高于其他处理，最高产量为9985 kg/hm2。拔节前群体茎蘖数增加较慢，但高峰苗数适宜，拔节后群体茎蘖数下降平缓，茎蘖成穗率显著高于其他处理，高于70%；生育中期和后期，群体叶面积指数较高，群体光合势高，光合生产力强，干物质积累量显著提高。随基蘖肥占总施氮量比例降低，成熟期氮素积累总量、氮肥表观利用率、氮肥农学利用率及氮肥偏生产力均呈先增加后减少的趋势，百公斤稻谷需氮量呈先减少后增加的趋势。6∶4和7∶3处理拔节前氮素积累量较少，拔节至抽穗期氮素积累量和成熟期积累量显著高于其他处理。6∶4和7∶3处理氮肥表观利用率、农学利用率及偏生产力显著高于其他处理，百公斤稻谷需氮量显著低于其他处理。氮肥表观利用率 与基蘖肥比例呈开口向下的二次曲线关系。同时该氮肥运筹模式可改善稻米加工品质、蒸煮食味和营养品质，但增加了稻米垩白率和垩白度，RVA谱特征值各指标不能同时达到最佳值。【结论】基蘖肥∶ 穗肥为 6∶4、7∶3的氮肥运筹方案，可使双季晚粳稻高产、优质、高效得到较好的协调统一。

Nitrogen managements of late japonica rice in double-cropping rice area

【Objectives】The indica rice has been planted as the major variety of late-season rice in double-cropping rice regions in South China. In recent years, due to the gradually increasing demand of japonica rice observed in most provinces of China, the project of indica to japonica in late season has been proposed in order to produce more japonica rice, which may benefit from the sufficient temperature and light in South China. To achieve high yield, good quality and high efficiency of japonica rice production, it is critical to determine the most effective split application of fertilizer nitrogen at the tillering and panicle stages. 【Methods】Therefore, field experiments were conducted at the farm of Zenxi Town, Shanggao County, Jiangxi Province, China in late rice-growing seasons in 2011-2012. Two hybrid japonica rice cultivars, i.e., Changyou-5 and Yongyou-8, were grown by applying basal-tillering-fertilizer and panicle-fertilizer in different proportions (i.e., 10∶0, 8∶2, 7∶3, 6∶4, 5∶5, 4∶6 and 3∶7), respectively at the same gross nitrogen application rate of 225 kg/ha. Subsequently, the effects of the nitrogen application strategies on yield and its formation, leaf area index(LAI), stems and tillers dynamic change, dry matter production and accumulation, nitrogen use efficiency and rice quality of late japonica rice were analyzed and compared. 【Results】It was found that the number of panicles decreased while the filled-grain percentage, 1000-grain weight and spikelets per panicle first increased and then decreased with decreasing basal-tillering-fertilizer proportion, and panicle-fertilizer in the proportions of 6∶4 and 7∶3 led to larger panicle population, bigger panicles, larger spikelet population, more stable filled-grain percentage and 1000-grain weight, and higher rice yields (as high as 9985 kg/ha). When the two treatments of 6∶4 and 7∶3 were compared, before jointing stage, the population of stems and tillers increased slowly to an appropriate peak value, and then decreased gently after jointing stage. The spike rate was significantly higher than that in the other treatments. During middle and late growth stages, the population had significantly higher dry matter production and accumulation with larger LAI and photosynthetic potential. It as also found that, when the ratio of basal-tillering fertilizer to total nitrogen decreased, the total N accumulation in the mature stage, the apparent nitrogen use efficiency (ANUE), agronomic efficiency (AE) and partial factor productivity of applied N (PFP) increased first and then decreased while the nitrogen requirement for 100 kg grain decreased first and then increased. The treatments with the proportions of 6∶4 and 7∶3 led to significantly higher total nitrogen accumulation, apparent nitrogen use efficiency (ANUE), agronomic efficiency (AE) and partial factor productivity of applied N (PFP) as well as lower nitrogen requirement for 100 kg grain than the other treatments from jointing stage to panicle stage. The relation between ANUE and ratio of basal-tillering-fertilizer could be represented by a quadratic curve opening downward. In addition, the application of basal-tillering-fertilizer and panicle-fertilizer in the proportions of 6∶4 or 7∶3 can also improve the cooking, eating and nutritional qualities of rice although the two treatments increased rice chalkiness grain percentage and degree of chalkiness, and they cannot improve the RVA profile characters. 【Conclusions】In general, the treatments with the proportions of 6∶4 and 7∶3 can achieve high-yield and good quality japonica rice production with high N use efficiency in double-cropping rice regions.