Jianhui LI, Baoan XU, Zhenming CANG, Qiuju WANG, Feng JIAO*, Ruichang ZHAI

1. Heilongjiang Bayi Agricultural University, Daqing 16319, China;

2. Heilongjiang Shuguang Farm, Jiamusi 15451, China;

3. Heilongjiang Beidahuang Rice Industry Group Co. Ltd., Harbin 15090, China

Nitrogen is an essential nutrition to plants, as it exerts significant impacts on the growth and yield of crops[1-4]. The rice yield largely depends on the accumulation and distribution of nitrogen in the nutritional organs and growth organs of plants[5-6].Generally speaking,the tiller stage to the flowering period are critical time for the rice to absorb nitrogen.During this period, the absorbed nitrogen is stored in the leaves[7].When rice enters into the flowering period, the nitrogen in the nutrition organs began to circulate to the seeds, in order to satisfy the seeds’needs of nitrogen[8-9].The absorption and circulation of nitrogen in the rice production need further investigation, and this in turn contributes to the further investigation and management of rice growth.

With regard to the current agricultural production, farmers apply chemical fertilizers reasonably,and enhance the fertilizer use efficiently. Therefore,the effect of nitrogen application on15N absorption and distribution of Longjing 31 and Kongyu 131 rice varieties was studied by 15N isotopic trace technique in this paper.

Materials and Methods

Tested materials and tests design

The field experiment was carried out in Heilongjiang Beidahuang Scientific and Technological Park. The soil was Albic planosol. The foundation fertility of soil before the experiment was 31.13 g/kg organics,163.51 mg/kg available nitrogen, 31.14 mg/kg available phosphorus, 116.65 mg/kg available potassium, 6.02 pH. We set out five treatments as N0,N1,N2,N3,and N4, and we applied 0, 90, 150, 210 and 270 kg/hm2of nitrogen for each treatment, as the percentage of base fertilizer,tiller fertilizer and panicle fertilizer was 4∶3∶3. The nitrogen source was urea(N,46%),phosphorus fertilizer was calcium superphosphate(P2O5, 17%), and 60 kg/hm2was applied. Besides, 90 kg/hm2of potassium sulfate (K2O, 50%) was applied.Phosphorus fertilizer was applied as the base fertilizer. 60% potassium was applied as base fertilizer, and the rest 40% was applied as the panicle fertilizer.

Meanwhile,small regions were divided for each treatment.PVC cylinder was put into the soil for 45 cm deep,and the PVC cylinder was 60 cm high and 25 cm wide. There was one spot for a seedling in each cylinder.The15N isotopic trace technique was adopted in each area, and the isotope was the15N trace urea(abundance 5%,Shanghai Research Institute of Chemical Industry). The experiment was repeated four times. In each treatment, the diameter of the hole for rice seedlings was 14 cm, the line distance was 30 cm. There were three strains in each hole.There were 7 lines in each treatment and the line length was 10 m.

The tested rice species include Longjing 31 and Kongyu 131. The seedlings were planted on May 15.The field management in other experiments was the same as that in the large field.

Sample collection and analyses

During the four critical growth periods,namely the tillering period,jointing period, flowering period and maturing period, there were three places to plant rice in each area. We isolated different organs based on stalk length,leaves and seeds. In the experiment,rice was harvested after complete maturing. The rice plants include stem leaves, seeds and roots based on different organs.All plants samples were cleaned with clean water and ionized water for many times.The plant samples were baked at 75 ℃. We analyzed the nutritional content in the plants.

The nitrogen in the plants was boiled with H2SO4-K2SO4-CUSO4[10],and was determined by the KjelFlex K360 nitrometer produced by BUCHI Company.The15N isotopic trace technique was determined by the Integra CN special isotope mass spectrometer produced by Europa Scientifi company.The nitrogen ratio in the plants was the result of plant N atom percent and the fertilizer N atom percent.

Data process and statistics analyses

All experiment data was processed by Excel 2003 and was analyzed by SAS9.2.

Results and Analyses

The amount of nitrogen in the rice plants during different growth period

According to Table 1, the amount of nitrogen was the most in the rice plants during the tiller period. With the growth of rice, the dry materials in rice accumulated, while the nitrogen in the plants gradually declined. This might because the rapid accumulation of dry materials in the plants diluted the nitrogen in the plants, and the nitrogen amount in the plants during the maturing stage was the lowest. During the final period of rice growth,the nitrogen in the nutritional organs moved to the storing organs, thus the nitrogen amount in the organs such as straws declined dramatically. The effects of different nitrogen level on the amount of N in rice were significant.The amont of nitrogen in the N0 treatment was lower than that of other treatments,and although the nitrogen content in different organs varied, the value increased along with the enhanced skills in nitrogen application. When the plants reached maturing period, it was shown that the nitrogen in Longjing 31 was higher than Kongyu 131. The difference of nitrogen in two rice species reached 0.01 significant level.

Table 1 The amount of N in the rice plants during different growth period %

The influence of different treatments on the accumulation of nitrogen in the rice plants

It is shown in Table 2 that nitrogen in the plant accumulates as the rice grows. Between the tiller period and jointing period, the amount of nitrogen in the plants was the largest, which was almost 40% of the amount of nitrogen during the entire growth period,while there was another peak of nitrogen accumulation during the early period of growth. Therefore, the absorption of nitrogen in the rice generally took place in the early period of growth, and the absorption of nitrogen in the growth period was little.The application of nitrogen treatment obviously facilitated the rice plants to absorb nitrogen. In terms of the rice plants at the same growing stage, the more nitrogen was applied, the more nitrogen accumulated in the plants. During the final period of rice growth,compared to N0, in the N1 treatment to N4 treatment, the absorption of nitrogen in Longjing 31 rose by 42.0%, 91.2%,116.9% , and 121.0% . Therefore,Longjing 31 was more sensitive than Kongyu131 in the aspect of nitrogen absorption.

The absorption and distribution of 15N in rice plants

It is suggested in Table 3 that amount of 15N in different parts of plants differed, and the amount of seeds in the plants was the highest,followed by that in the straw and leaves. The amount of nitrogen in the roots was the least. The reason for such phenomena was that the amount of dry materials in each organs of plants was different,and the amount of dry materials in the roots was particularly little.The dry materials in the harvest organs of Longjing 31 was 5.2 to 6.2 times that of the underground roots, while the dry materials in the stem and leaves were 4.4 to 5.5 times that of the roots. By comparing different species,we found that the nitrogen in the harvest organs of Longjing 31 in N1, N2, N3 and N4 treatment was higher than that of Kongyu 131 by 27.9%,37.5%,23.9%and 33.0%, respectively. There were no distinct dif-ferences in other organs. The amount of15N differed in the aspect of organs,stems and leaves. The accumulation of15N in the harvest organs of Longjing 31 was 3.1% to 7.5% higher than Kongyu 131,while the accumulation of stems and leaves in other organs decreased by 3.2%to 7.9%.

Table 2 The absorption of N during different growth periods

Table 3 15N absorption and distribution

Conclusions and Discussions

So far, the study of nitrogen has largely focused on the accumulation dynamics of nitrogen in the rice at different growth stage. Cao Hongsheng et al.[11]suggested that the growth of tiller and spike needs nitrogen the most.Wang Xiuqing[12]believed that the absorption of nitrogen in the rice plants peaked from the jointing period to the spike period. 50% nitrogen was absorbed in the growth of rice. Experiment showed that the amount of nitrogen was the most in the early period,which was 40% of the total amount during the entire growth period. The peak of nitrogen came before the tiller period. Therefore, the demand of nitrogen was pretty high in the early stage of growth.An environment full of nitrogen can promote the growth of leaves, enlarge leaf area and provide insurance for the successful photosynthesis[13], and promote the addition of effective number of tiller, in order to reduce the unsuccessful grouting in some seeds,and to raise the yield[14].

The isotopic trace experiment indicated that with the addition of nitrogen, the accumulation of15N decreased in the harvest organs of rice,but the accumulation in the stem and leaves rose. The15N in Longjing 31 and Kongyu 131 differed insignificantly.The nitrogen improved the nutrition surroundings of rice, and enhance the accumulation of nitrogen in the nutritional organs. Experiment also suggested that the nitrogen in the fertilizer was distributed as seeds ＞stems and leaves ＞roots, and the accumulation of15N in the rice decreased. There were two reasons for such phenomenon. First of all, the biological yield of the root was little,which directly led to the low accumulation of15N.Secondly,with the rapid growth of nutritional organs, those nitrogen moved upward to the aboveground[1].The accumulation of15N in the seeds of Longjing 31 was higher than Kongyu 131,while on the contrary,the amount of15N in the stem part of Longjing 31 was lower than Kongyu 131. In general,the redistribution and rotating efficiency of nitrogen in the rice are essential to the yield of Longjing 31.

[1]JIAO F,WU JH,YU LH,et al.15N Tracer technique analysis of the absorption and utilization of nitrogen fertilizer by potatoes [J]. Nutrient Cycling in Agro ecosystems,2013,95(3):345-351.

[2]JIAO F(焦峰),HE HX(賀海霞),WEI XB(魏賢斌),et al.Effects of different nitrogen application rates on tuber bulking,yield and vitamin C content of potato(不同氮水平對馬鈴薯塊莖增長、 產(chǎn)量和維生素含量的影響)[J]. Journal of Heilongjiang Bayi Agricultural University(黑龍江八一農(nóng)墾大學(xué)學(xué)報(bào)), 2013, 25(4):1-3.

[3]PAN SG (潘圣剛),HUANG SQ (黃勝奇),QU J (翟晶),et al.Effects of nitrogen rate and its basal to dressing ratio on uptake,translocation of nitrogen and yield in rice (氮肥用量與運(yùn)籌對水稻氮素吸收轉(zhuǎn)運(yùn)及產(chǎn)量的影響)[J].Soils(土壤),2012,44(1):23-29.

[4]MENG LY(孟令遠(yuǎn)),MA GS(馬光恕).Effect of Euonymus alatus (Thunb.) sleb protective enzymes and soluble protein content in the different amount of nitrogen(不同施氮量對衛(wèi)矛保護(hù)酶活性及可溶性蛋白含量的影響)[J]. Journal of Heilongjiang August First Land Reclamation University(黑龍江八一農(nóng)墾大學(xué)學(xué)報(bào)),2014,26(5):1-4.

[5]NTANOS D A,KOUTROUBAS S D.Dry matter and N accumulation and translocation for Indica and Japonica rice under Mediterranean conditions [J]. Field Crops Research,2002,74(1):93-101.

[6]LI WJ(李文軍),XIA YQ(夏永秋),YANG XY (楊曉云), et al. Effects of applying nitrogen fertilizer and fertilizer additive on rice yield and rice plant nitrogen uptake,translocation, and utilization (施氮和肥料添加劑對水稻產(chǎn)量、 氮素吸收轉(zhuǎn)運(yùn)及利用的影響)[J].Chinese Journal of Applied Ecology(應(yīng)用生態(tài)學(xué)報(bào)),2011,22(9):2331-2336.

[7]JIANG L G,DAI T B, JIANG D.Characterizing physiological N-use efficiency as influenced by Nitrogen management in three rice cultivars [J]. Field Crops Res,2004,88(2):239-250.

[8]DUAN YH (段英華),ZHANG YL (張亞麗),SHEN QR(沈其榮),et al.Effects of partial replacement of NH4+by NO3-on nitrogen uptake and utilization by different genotypes of rice at the seedling stage(增硝營養(yǎng)對不同基因型水稻苗期氮素吸收同化的影響)[J].Plant Nutrition and Fertilizer Science(植物營養(yǎng)與肥料學(xué)報(bào)),2005,11(2):160-165.

[9]YAN FJ(嚴(yán)奉君),SUN YJ(孫永健),MA J (馬均), et al. Effects of wheat straw mulching and nitrogen management on grain yield, rice quality and nitrogen utilization in hybrid rice under different soil fertility conditions(不同土壤肥力條件下麥稈還田與氮肥運(yùn)籌對雜交稻氮素利用、 產(chǎn)量及米質(zhì)的影響)[J]. Chinese Journal of Rice Science(中國水稻科學(xué)),2015,29(1):56-61.

[10]ZHANG ZL(張志良).Botanic physiology experiment guidance(植物生理學(xué)實(shí)驗(yàn)指導(dǎo))[M]. Beijing: Higher Education Press (北京: 高等教育出版社),2010:35-36.

[11]CAO HS (曹洪生), HUANG WS (黃王生),MIAO BS(謬寶山).Studies on the nitrogen absorption analysis and fertilizer technology (兩種類型中粳稻吸氮分析及施肥技術(shù)研究)[J].Journal of University of Science and Technology of Suzhou:Social Science(蘇州科技學(xué)院學(xué)報(bào):社會(huì)科學(xué)版),1992,9(1):3 5-41.

[12]WANG XQ (王秀芹), ZHANG HC (張洪程),HUANG YZ (黃銀忠),et al.Effects of N-application rate on the characters of uptake nitrogen and nitrogen recovery of different rice varieties(施氮量對不同類型水稻品種吸氮特性及氮肥利用率的影響)[J].Journal of Shanghai Jiaotong University (上海交通大學(xué)學(xué)報(bào): 農(nóng)業(yè)科學(xué)版),2003,21 (4):325-330.

[13]CHEN JP(程建平),CAO CG(曹湊貴),CAI ML (蔡明歷), et al. Effects of different nitrogen nutrition and soil water potential on physiological parameters and yield of hybrid rice (不同土壤水勢與氮素營養(yǎng)對雜交水稻生理特性和產(chǎn)量的影響)[J]. Plant Nutrition and Fertilizer Science (植物營養(yǎng)與肥料學(xué)報(bào)),2008,14(2):199-206.

[14]XU FX(徐富賢), XIONG H(熊洪), XIE R(謝戎),et al.Advance of rice fertilizer-nitrogen use efficiency(水稻氮素利用效率的研究進(jìn)展及其動(dòng)向)[J].Plant Nutrition and Fertilizer Science(植物營養(yǎng)與肥料學(xué)報(bào)), 2009, 15 (5): 1215-1225.