Effect Of Nitrogen On Photosynthetic Characteristics And Yield Of Different Spike Types Of Super Early Rice

Early rice grown in the middle and lower reaches of the Yangtze River is characterized by high temperature sensitivity,low photo-sensitivity and short growing period.The high frequency of rainy days during the growing season of early rice makes the research on photosynthetic physiological characteristics of its field nitrogen regulation lag behind that of middle and late rice,and the environmental problem of eutrophication of water bodies due to excessive fertilization is widespread.In order to clarify the effects of nitrogen regulation on photosynthetic growth characteristics,to reveal the necessity of applying spike fertilizer to plant super high-yield early rice and to establish an environmentally friendly cultivation method.Therefore,the super early rice the large-spike variety Zhongzao 39,the multi-spike variety Lingliangyou 268 and the spike grain balanced variety Ganxin 203 were used the test materials.A systematic study for the effects of nitrogen regulation on photosynthetic characteristics and yield of different spike types of super early rice were carried out with different nitrogen application rates and nitrogen application ratios at different growth stages.In 2019,the three varieties of super early rice were planted in Luiyang city Hunan province,treated with four nitrogen fertilizer amount and applied ratio of T1(0 kg·hm^-2of N),T2(112.5 kg·hm^-2of N),T3(150.0 kg·hm^-2of N,and the ratio of basal fertilizer)and T4(187.5 kg·hm^-2of N).In the 2020,two super early rice varieties Lingliangyou 268 and Ganxin 203 were planted in Liuyang City Hunan Province.The experiment was conducted at nitrogen content of 150.0 kg·hm^-2,and five treatments with different ratios of basal fertilizer,tiller fertilizer and spike fertilizer:A（no fertilizer）,B（one-time application）C（basic fertilizer,tiller fertilizer,the nitrogen ratio is 7∶3）,D（basal fertilizer,tiller fertilizer and spike fertilizer the nitrogen ratio is 6∶3∶1）,and E（basal fertilizer,tiller fertilizer and spike fertilizer the nitrogen ratio is 5∶4∶1）.The main results were as follows:1.The avaliable spike number,three upper leaves area,relative chlorophyll content,net photosynthetic rate,electron transfer rate（ETR）and apprant quantum yield（AQY）of three varieties treated with T3 and T4 were increased to compare with those of T1 and T2.2.The yield of the four treatments with different nitrogen application rates were T3>T4>T2>T1 from high to low,and T3 had the highest harvest index and yield of the three varieties.The yields of Lingliangyou 268,Zhongzao 39 and Ganxin 203 were increased by23.61%,31.40%and 34.77%respectively compared with T1.The above results showed the best overall evaluation of photosynthetic characteristics and yield of the three super early rice varieties at T3,indicating that the(N 150.0 kg·hm^-2)nitrogen application at T3 was the most appropriate.3.The ratio of D nitrogen application could increase the relative chlorophyll content of the upper three leaves,increase the leaf thickness,maintain a high net photosynthetic rate,and increase effective ear number after the full ear stage.At maturity,Lingliangyou 268 and Ganxin 203 maintained the high net photosynthetic rate of 20.77μmol·m^-2·s^-1and 23.89μmol·m^-2·s^-1respectively.4.The yield of each treatment from high to low was D>E>C>B>A,and the yield of D was significantly higher than that of A,B and C.Compared with A.The output of Lingliangyou 268 and Ganxin 203 D increased by 61.70%and 70.65%respectively.Compared with A,the nitrogen absorption of Lingliangyou 268 and Ganxin 203 treatment D increased by 146.22%and 177.84%respectively.It shows that the fertilization ratio of D is beneficial to increase the nitrogen uptake and yield of super early rice.The results of the overall study showed that the amount of pure nitrogen is 150.0kg·hm^-2,and the ratio of basal fertilizer to basal fertilizer to spike fertilizer was 6∶3∶1 are suitable.In addition to the basal fertilizer and tiller fertilizer,the application of additional spike fertilizer can effectively improve the leaf area of upper three leaves,photosynthetic rate,effective spike number,biomass and yield of different spike structure types of super early rice.