The Differences Of Super Hybrid Rice Yield And Nitrogen Use Efficiency In Different Years

In order to study N-use efficiency,dry matter accumulation and the grain yield potential of super hybrid rice bred in different years,the field experiments with different years varieties of super hybrid rice(Liangyoupeijiu,Y-liangyou-1,Y-liangyou-2,Y-liangyou-900and Chaoyou-1000)were conducted under the different nitrogen level(0,210,300 and 390kg N/hm~2)condition in Ningxiang county of Hunan province.The results are as follows:Significant yield differences of different varieties were found in two years,of which Chaoyou-1000 produced the highest yield averaged in two years(10.02 t/hm~2),followed by Y-liangyou-900,Y-liangyou-2,Y-liangyou-1 and Liangyoupeijiu,which was up to 9.94t/hm~2,9.71 t/hm~2,8.60 t/hm~2,8.13 t/hm~2 respectively.The yield of the third phase super hybrid rice was significantly higher than that of the first phase or the second phase super hybrid rice.Super rice yield showed the significant differences under the condition of different fertilizer rates,N3 treatments(390 kg/hm2)showed the highest of 10.30 t/hm~2averaged in two years,and others followed by N2(300 kg/hm~2),N1(210 kg/hm~2)and N0(0kg/hm~2)with the yield of 10.27 t/hm~2,9.48 t/hm~2,7.10 t/hm~2 in turn.Yield difference between N2 and N3 was not significant,but significantly higher than that of N1 and N0.The nitrogen use efficiency of N2 treatment was higher than that of other nitrogen treatments.There were significant differences of the yield components of different varieties of super hybrid rice,the same results were founded in two years.The effective panicle number per unit area of both Chaoyou-1000 and Y-liangyou-900 were significantly lower than that of the other three cultivars,but the total spikelet number per panicle was significantly higher than that of the other three cultivars.At the same time,the total spikelet number of Y-Liangyou-900,Chaoyou-1000 and Y-Liangyou-2 were significantly higher than that of Y-Liangyou-1 and Liangyoupeijiu.Seed setting rate of Y-Liangyou-1 was the highest,the others followed by Y-Liangyou-2,Chaoyou-1000,Y-Liangyou 900 and Liangyoupeijiu.The 1000-grain weight of Y-Liangyou-1 was the highest,the others followed by Liangyoupeijiu,Chaoyou-1000,Y-Liangyou-2,Y-Liangyou-900.It can be seen that the super rice cultivars changed from multiple panicle type varieties to large panicle type.The grain yield increased from Liangyoupeijiu to Y-Liangyou-1 was mainly owing to the increase in both seed setting rate and 1000-grain weight and the yield increased from Y-iangyou-1 to Y-Liangyou-2 was due to a large increase in the spikelet number per panicle,and yield increased from the Y-Liangyou-2 to Y-Liangyou-900 and Chaoyou-1000 was due to the increase in grain weight and seed setting rat.Super rice with a high spikelet number was very important,high yield should ensure on the basis of higher spikelet number as well as to maintain the higher seed rate and the 1000-grain weight.The dry matter yield and harvest index of different super hybrid rice were significantly different.The total dry matter weight of Chaoyou-1 is the highest(1619.7g/m~2),the others followed by Y-Liangyou-2(1592.7 g/m~2),Y-Liangyou-900(1571.0 g/m~2),Y-Liangyou-1(1434.2 g/m~2)and Liangyoupeijiu(1420.3 g/m~2).As for the dry mater production under the condition of different fertilization treatments,N3 showed the highest total dry matter weight and N0 showed the lowest.Chaoyou-1000 showed the highest harvest index among the five varieties,and the grain yield decreased with the increase of nitrogen application rate.The correlation analysis showed that the yield of different super hybrid rice was positively correlated with the dry matter production at maturity.Therefore,it is an effective way to improve the yield of super hybrid rice by increasing the dry matter production as well as the higher harvest index.Nitrogen production efficiency of grains,absorption use efficiency,physiological use efficiency,agronomic use efficiency and partial productivity of tested five varieties decreased with the increase of nitrogen fertilizer application rate,of which the highest was111.98 kg/kg,42.79%,33.51 kg/kg,14.2 kg/kg 3,46.07 kg/kg respectively when the nitrogen fertilizer level was 210 kg/hm~2.There were differences of absorption use efficiency,physiological use efficiency,agronomic use efficiency and partial productivity among tested varieties,but the rule was not obvious.It can be made conclusion that higher yield of super hybrid rice was due to both higher dry matter accumulation and harvest index.From the angle of yield components,higher yield of super hybrid rice should be on the base of large panicle size,higher seed setting rate and the 1000-grain weight.The nitrogen response sensitivity of super rice varieties became stronger with the new super hybrid rice variety releasing.As for the same variety,the nitrogen use efficiency decreased with the increase of fertilizer application.