Effects Of Nitrogen Application On The Characters Of Rice Canopy During Grain Filling Stage

Studies of three different nitrogen application methods about QianCu, YouZhong and PingHeng on rice canopy leaf characteristics in filling stage with rice varieties Wuyunjing23(2645) and Yongyou8 as materials in the farm of Yangzhou University was put in practice during 2008-2009. The total nitrogen application rate was all 18kg/mu. Analysis the canopy structure before and after heading of rice, including plant height and the leaf length of canopy, leaf size and leaf area index, leaf SPAD values, nitrogen rate of leaves and stems, canopy light distribution and leaf photosynthetic rate, the changes of dry matter of rice in filling stage, the dry matter weight and nitrogen content of different parts of ear grains and rice yield. The main results are as follows:1,The height of rice plants with the panicle increased the proportion of nitrogen increased, PingHeng>YouZhong>QianCu. The length of flag leaf was PingHeng > YouZhong> QianCu, QianCu and PingHeng, the order of rice canopy leaf length was 2>3>4>1, but that of YouZhong was 2>1>3>4. The SPAD values of heading leaves of each treatment were higher than the lower, And 20 days after heading, YouZhong SPAD values of rice leaves still maintain a very high level, the SPAD values of the same leaves in different treatment were YouZhong>PingHeng>QianCu.2,Leaf area of variety Yongyou8 in filling stage was significantly greater than cultivars 2645, and rice leaf size was different in different nitrogen application. Leaf area of YouZhong was the first leaf> second leaf> third leaf. The levels Leaf area index of each different treatment from the top of rice canopy to bottom increased first and then decreased. The leaf area index of the third and fourth levels was the maximum. The leaf area index of the third and fourth levels was PingHeng>QianCu>YouZhong, the other layers were YouZhong>PingHeng >QianCu.3,The nitrogen content of leaves and stems and sheaths of the first level at flowering and grain filling stage of different treatment was the maximum, decreased from top to bottom. From the perspective of different nitrogen application, the nitrogen application rate of rice canopy leaves, stems and sheaths preformed YouZhong >PingHeng > QianCu.4,Two rice cultivars with different treatment, canopy light intensity level dropped significantly, reducing transmittance also showed a significant decline. in the leaves of different treatments of light intensity and light transmission performance were QianCu>YouZhong>PingHeng.5,Canopy photosynthetic rate of different levels were the first leaf> second leaf> third leaf, with the growth after rice heading, different leaves of rice canopy photosynthetic rates increased slightly for the first then decreased. The leaf photosynthetic rate of rice variety Yongyou8 at every level were higher than variety 2645. The canopy photosynthetic rate of the nitrogen application treatment of YouZhong was significantly higher than QianCu and PingHeng.6,The dry weight of rice leaf, sheath and stem decreased during filling stage the dry weight of ears and total dry weight increased during growing period. Under the different conditions of nitrogen application, the dry weight of ears and total dry weight show YouZhong > PingHeng > QianCu.7,The effect of nitrogen application on dry weight of panicle grains was that, the dry weight of YouZhong of rice varieties 2645 was the maximum, early stage of QianCu was slightly higher than PingHeng, PingHeng day after heading 42d and 49d was slightly higher than QianCu. The effect of nitrogen application on dry weight of Yongyou 8 was different, dry weight in late stage of PingHeng was higher. the dry weight of rice heads of grain on each handle, middle and lower parts and total weight of ears increased with rice development, the dry weight of all parts of rice 2645 was middle> upper> lower, while the dry weight of rice varieties Yongyou 8 was that upper was slightly larger than middle, both were larger than lower.The nitrogen rate of rice ears for each upper, middle and lower part increased with the process of rice growing. The nitrogen rate of two rice cultivars after heading showed PingHeng >YouZhong >QianCu. The nitrogen rates of 2645 was in general middle> upper> lower, while the nitrogen rates of Yongyou 8 was upper> middle> lower.8,Effects of different nitrogen application on rice yield were YouZhong>PingHeng>QianCu. Nitrogen increased slightly in later stage, on the based that the spike decreased slightly, but the number of grains per panicle increased significant, and expanded the storage capacity, so production increased significantly.In summary, when the nitrogen application rate was 18 kg/mu under this experimental condition, nitrogen applied in the stage of 4 and 3 leaves remaining from the top of YouZhong, it was the high efficient stage to apply nitrogen. The canopy characteristics of two rice varieties were more appropriate, more conducive to high yields of rice. The panicle fertilizer of PingHeng was large, it resulted in smaller spike, lower yield. The tillering fertilizer application of QianCu was large, it resulted in large group, multi-spike, smaller panicle, it was difficulty to get higher rice yield.