| Studies were conducted in the experimental farm of Yangzhou University in 2015 and 2016 using Yongyou medium-maturing Japonica/Indica rice of suitable growth period in Lixia-River zone as test materials,and conventional japonica rice and indica hybrid rice as control materials.A split-plot design was used in this study with nitrogen application level(0,187.5,262.5 and 337.5kg hm-2)as the main plot and rice varieties as the split plot.The yield formation traits of Yongyou Medium-Maturing japonica/indica hybrid rice and the effect of nitrogen application level on yield,dry matter accumulation,and nitrogen absorption and utilization were systematically studied,which would provide theoretical basis for high-yielding cultivation of japonica/indica hybrid rice.The main results were as follows:1.Grain yield of Yongyou medium-maturing japonica/indica hybrid rice under 262.5 kg hm-2 nitrogen application level were 11.4 t ha-1 and 11.0 t ha-1,respectively which were significantly higher than that in the control materials in 2015 and 2016.Analysis on the factors of yield composition showed that,Yongyou medium-maturing japonica/indica hybrid rice had more spikelets per panicle and total spikelets,less panicles per square meter and 1000-grain weight,and similar seed setting rate compared with the control materials.In addition,the dry matter weight at heading and maturity and dry matter accumulation after heading of Yongyou medium-maturing japonica/indica hybrid rice was larger than the control materials.Compared to the control materials,the grain weight and grain density per panicle of Yongyou medium-maturing japonica/indica hybrid rice were higher,and the panicle length was between the two control materials,of which 80%fulfilled grains were grown on the up and middle part of the panicle.The leaf shape and posture of Yongyou medium-maturing japonica/indica hybrid rice were better than the others,with wider top-three leaves,moderate leaf length and basic leaf angle,and smaller drooping angle in the top-three leaves.Compared with the control materials,the plant height,gravity center high,and the lodging index of basal three internodes of Yongyou medium-maturing japonica/indica hybrid rice were ranked in the second place,of which the bending moment,break resistance,dry weight of stem,sheath and unit internode at maturity stage were larger.These illustrated enriched stem and increased lodging resistance of Yongyou medium-maturing japonica/indica hybrid rice.2.With the increased nitrogen application level,grain yield of Yongyou medium-maturing japonica/indica hybrid rice was increased,and obtained the highest grain yield under 337.5 kg hm-2 nitrogen application level.When increasing the nitrogen application level,panicles per square meter were increased,spikelets per panicle were firstly increased and then decreased,seed-setting rate and 1000-grain weight were decreased.Compared with the control materials,the yield and spikelets per panicle of Yongyou medium-maturing japonica/indica hybrid rice all were highest at different nitrogen application level.In addition,with the increased nitrogen application level,the maximum rate of dry matter accumulation of test materials was increased gradually,the time of reaching the maximum rate of dry matter accumulation was earlier,and the effective dry matter accumulation period was prolonged,dry matter accumulation during middle and late period was increased(which was related to the prolonged days,increased rate of dry matter accumulation during that periods),and a significant positive correlation with grain yield(r=0.959*)occurred.As observed in the study,the dry matter accumulation rate of Yongyou medium-maturing japonica/indica hybrid rice was lower than indica hybrid rice and higher than japonica conventional rice;and the effective accumulation duration of Yongyou medium-maturing japonica/indica hybrid rice and japonica conventional rice were longer than indica hybrid rice;but the duration of dry matter accumulation during middle and late period of Yongyou medium-maturing japonica/indica hybrid rice were longer than the other materials.Opposite to the dry matter accumulation of leaf,the dry matter accumulation ratio of stem and sheath at the test growth stages and panicle at maturity stage showed decreased trends with the increased nitrogen application level.Among the materials,the Yongyou medium-maturing japonica/indica hybrid rice' dry matter accumulation ratio of stem and sheath,leaf were ranked in the second place,and dry matter accumulation ratio of panicle at maturity was similar with indica hybrid rice,all were higher than conventional rice.3.Along with the increase in nitrogen application level,the nitrogen rate and nitrogen accumulation at test growth stages,and nitrogen accumulation ratio after jointing of Yongyou medium-maturing japonica/indica hybrid rice were increased,moreover,a significant positive correlation between grain yield and the nitrogen accumulation at heading and maturity stages(r=0.955*?0.952*);the nitrogen accumulation of different parts of plants at heading and maturity were increased but the nitrogen accumulation rate of different parts of plant showed different trend,showing trends that nitrogen accumulation rate in stem and sheath at heading and maturity and in panicle at maturity were decreased,and in leaf were increased;translocation of sheath and leaf after heading were increased,while nitrogen translocation efficiency and contribution ratio of these organs to panicle were all decreased.;nitrogen agronomic efficiency,nitrogen physiological efficiency,nitrogen efficiency of grain production,nitrogen matter production efficiency decreased,and increased N-requirement per 100 kg grain.Among all materials,Yongyou medium-maturing japonica/indica hybrid rice had a higher nitrogen content and nitrogen accumulation during middle and late growth periods,but lower nitrogen translocation efficiency,contribution rate of nitrogen transport to panicle,nitrogen physiological efficiency,nitrogen dry matter production efficiency. |
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