南方粳型超级稻氮肥群体最高生产力及其形成特征的研究

在大田机插条件下,以南方稻区5个粳型超级稻(南粳44、宁粳1号、宁粳3号、扬粳4038、武粳15)为材料,同生育期常规粳稻武运粳7号为对照,在其他栽培措施统一在最佳技术指标前提下,设置7个氮肥水平(0、150.0、187.5、225.0、262.5、300.0和337.5kg.hm-2),从中得出各品种在这7个氮肥水平下出现的最高生产力,并将其定义为氮肥群体最高生产力。对5个超级稻氮肥群体最高生产力及其构成、群体生长发育动态、株型以及倒伏性状等方面进行系统的比较研究。结果表明,超级稻氮肥群体最高生产力为10.51(10.30～10.68)t.hm-2,极显著高于对照(9.77～9.82t.hm-2),增产幅度达5.2%～8.7%。与对照相比,超级稻氮肥群体最高生产力群体穗数多,穗型大,群体颖花量高(42442.11～44873.23×104.hm-2),结实率和千粒重与之相当;群体茎蘖机插后早发快长,有效分蘖临界叶龄期苗数略高于预期穗数,有效分蘖临界叶龄到拔节期茎蘖增长平缓,高峰苗出现在拔节期,数量适中,为预期穗数的1.4～1.5倍,此后群体平缓下降,至抽穗期基本稳定,最终成穗率高(66.9%～70.4%);其群体叶面积动态与茎蘖动态基本一致,最大叶面积指数出现在孕穗期,为7.72～7.97,此后平缓下降,成熟期保持在较高的水平上(3.30～3.74);干物重积累方面,移栽到有效分蘖临界叶龄期较对照高,有效分蘖临界叶龄到拔节期较对照低,拔节后积累速度较快,至抽穗期为10.80～11.08t.hm-2,抽穗到成熟期干物质积累量6.78～7.22t.hm-2,成熟期总干物重17.58～18.29t.hm-2,显著或极显著高于对照;根冠比和根系干重均高于对照,随着生育期的推移,超级稻优势更为明显,生育后期根系活力强(抽穗到蜡熟期平均伤流量3.53～3.74g.m-2.h-1)。超级稻群体形成特征:高秧苗素质促进低位分蘖发生,精确群体起点稳定提高穗数;生育中期干物质积累高,叶面积大,株型直挺,有效叶面积率和高效叶面积率高,源库流畅;生育后期茎鞘输出大,2次增重高,根群强健,支撑着高光效灌浆结实层的安全充实。氮肥群体最高生产力水平下,超级稻穗多粒大,群体颖花量大,需氮量大,产量潜力高;生育中后期光合生产能力强,充实量大;群体株型改善,抗倒支撑强,适宜用作机插。

THE HIGHEST POPULATION PRODUCTIVITY OF N FERTILIZATION AND ITS FORMATION CHARACTERISTICS ON JAPONICA SUPER RICE IN SOUTH CHINA

A field experiment was conducted using five japonica super rice cultivars in south China(Nanjing44,Ningjin1,Ningjing3,Yangjing4038,Wujing15) as materials and a conventional japonica rice cultivar Wuyunjing7 which had the same growing period as CK to achieve the highest productivity of all cultivars under seven nitrogen fertilization levels(0,150.0,187.5,225.0,262.5,300.0,337.5kg·hm-2).Meanwhile,the grain yield and its components,dynamics of population stems and tillers,leaf area index,dry matter weight,root-shoot ratio and weight of dry matter of root,plant type,lodging characteristics were studied systematically.Results showed that the highest population productivity of N fertilization in super rice was 10.51(10.30~10.68) t·hm-2,significantly higher than CK(9.77~9.82t·hm-2),with the increasing range of 5.2%~8.7%.Compared with CK,more panicles per unit area,spikelets per panicle and population spikelets(42442.11~44873.23×104·hm-2) were observed under the highest population productivity of N fertilization in super rice,with the roughly same level of seed-setting rate and 103-grain weight.In comparison with CK,number of stems and tillers rose faster to a suitable case with super rice at the highest population productivity of N fertilization,slightly higher than expected number of panicles at the critical leaf-age for productive tillers stage,and then increased slowly to the peak with an appropriate number(1.4~1.5 folds of expected panicle number).After that,it decreased gently and ultimately arrived at a significantly higher rate of productive tillers/total tillers(66.9%~70.4%).Dynamics of leaf area index at the highest population productivity of N fertilization in super rice developed the same tendency as dynamics of population stems and tillers,and the maximal leaf area index(7.72~7.97) appeared at the booting stage,and then decreased stably to a high level of 3.30~3.74 at maturity stage.As for the dry matter accumulation,the highest population productivity of N fertilization in super rice showed more advantages than CK from transplanting to critical leaf-age for productive tillers and lower accumulation from critical leaf-age for productive tillers to jointing,and then accumulated fast to 10.80~11.08t·hm-2 at heading stage and 17.58~18.29t·hm-2 at maturity stage(6.78~7.22t·hm-2 from heading to maturity),significantly higher than CK.Root-shoot ratio and weight of dry matter of root at the highest population productivity of N fertilization in super rice were significantly higher than CK.As the advancement of growth and development stage,the advantages went larger and larger,additionally with strong activity(root exudates 3.53~3.74g·m-2·h-1 from heading to waxy stage) at the later period.The formation characteristics were as follows.Firstly,low leaf position tillers came out quickly on the basis of high seedling quality so that panicles increased stably at the precise population starting point.Secondly,source coordinated with sink smoothly with the help of high ratio of leaf area of productive tillers and ratio of leaf area from flag leaf to 3rd leaf,as well as straight and erect plant type,in the context of high dry matter accumulation and leaf area.Finally,grain-filling layer of high use efficiency of solar energy was supported by large output of stems and sheaths,high second weightening and strong root.At the highest population productivity of N fertilization,due to possessing more panicles,spikelets per panicle,population spikelets,N uptake and grain yield,super rice was suitable for mechanical transplanting based on owning strong photosynthetic production capacity and large total filling,improved plant type and strong resistance lodging.