Technology, Nanjing, Jiangsu, China. Environmental and Safety Engineering, Jiangsu University, Zhenjiang, Jiangsu,China

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1 Advanced Materials Research Submitted: ISSN: , Vols , pp Accepted: doi: / Online: Trans Tech Publications, Switzerland Study on denitrification intensity in rice rhizosphere soil under water management model Han-Xiang Chen 1,a, Ge-Lan Ma 1,b,Zhi-Gang Chen* 2,c, Lei Chen 2,d, Ke Zhang 2,e 1 School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, China 2 Modern Agricultural Equipment and Technology Education Ministry Key Laboratory,School of Environmental and Safety Engineering, Jiangsu University, Zhenjiang, Jiangsu,China a williamchensong@126.com, b magelan@nuist.edu.cn, c chenzg01@126.com d jinglan2008.ok@163.com, e zklxs0819@163.com *corresponding author:zhi-gang Chen,chenzg01@126.com Keywords: Water Management;Denitrification Intensity; Rice; Rhizosphere Soil Abstract. A typical rice field ecosystem as the research object, using the indoor pot experiment to study the three kinds of water driven (shallow layer of continuous irrigation (C), alternating wet and dry (J), and water control mode (G)) on the effect of rice rhizosphere soil denitrification intensity. Effect of changes in soil moisture caused by the three different irrigation patterns on different growth stages of rice on rhizosphere denitrification was comparatively analyzed,referring to the rhizosphere denitrification capacity during different rice growth stage.the results showed that: soil denitrification intensity with different water managements changed significantly, showing C>J>G. And with the growth of plants, under three different water managements, denitrification intensity showed a downward trend. Mature reached to a minimum. All have to be higher than control groups. Introduction Greenhouse gases caused by the warming of global climate change as a major environmental problem, which has caused widespread concern in the international community. Denitrification is an important part of the nitrogen cycle in agroecosystems. Denitrification is an important mechanism of causing the loss of gaseous nitrogen. The intermediate product N 2 O is one of the important factors causing by global warming. Therefore, considerable attention has been focused on farmland denitrification processes and the impact of nitrous oxide(n 2 O) emitted from the earth s surface on amounts of stratospheric ozone. Denitrification process is that denitrifying bacteria uses nitrate nitrogen as an electron acceptor for metabolism, and ultimately transforming into gaseous nitrogen or nitrous oxide from the system in the process [1-2].Denitrification process is considered to be microbial processes. All external factors affecting microbial activity will affect the denitrification process. Research showed that denitrification rates must be higher than single anaerobic or aerobic environment, when sediment exists in both the anaerobic zone and aerobic zone [3-4].These zones often have been seen in the plant root zone or water level fluctuations and ecotone zone. Particularly in the most typical example of rice ecosystem. Among them, the plant rhizosphere exists oxidation-facultative-anaerobic microhabitats. So that different regions of the microbial flora cooperate with each other together, which will eventually release out nitrogen in the form of N 2 O or N 2. This plays an important role in agricultural ecosystem biogeochemical cycles aspects. Meanwhile, the rice fields are frequent cyclical irrigation and drainage. These often caused by alternating wet and dry soil aerobic zone into anaerobic zone in rice ecosystem. Or anaerobic zone has became aerobic district. So that it made paddy soil in anaerobic, aerobic or facultative aerobic habitats, leading to soil denitrification process, and ultimately accelerate the N 2 O emissions. Therefore, regular changes of water may be impact factors and key driving factors of rhizosphere denitrification in the rice ecosystem. Thus,researched changes of rice rhizosphere soil denitrification intensity on different water managements. From the perspective of denitrification clarified rhizosphere soil of rice denitrification All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-11/05/16,09:38:59)

2 Advanced Materials Research Vols process. This will provide a theoretical basis for wetland rice biogeochemical cycling of nitrogen and the control of greenhouse gas N 2 O emissions. Materials and methods Experimental materials and methods were as described in the literature [5]. Sample Determination. First, the collected soil samples were processed at low temperature freeze-drying. Test equipment model:lgj-12 freeze dryer (Beijing Songyuan Huaxing Technology Development Co., Ltd.). After the cold-dry, grinding sieving (0.125mm mesh),then placed in a sterile sealed bags and stored in -25 refrigerator for spare. Then, according to the literature [6] method measured soil denitrification intensity; according to the literature [7] measured soil nitrate content. Statistical Analysis Methods. Collation of data and statistical analyzes were performed using Excel2008 and SPSS16.0 software. Experimental Results And Analysis Figure 1 was the change process of soil denitrification intensity in a rice and no plant control system under different water management. Under three kinds of water modes, soil denitrification intensity have shown decreasing trends with rice growth. Denitrification intensity was the highest in tillering, while the lowest in maturity, comparing to tillering lower in booting stage. This was because tillering was the stage of rapid growth of rice. And experiments showed that either the rice abovegroud, roots or plants, fresh weight were significantly increased with the extension of the rice the growth period. Yi-lin Li, Ya-li Zhang et studies have shown that the dry weight of root was concentrated expression of the root growth situation, which reacted the extent of developed roots [8]. Therefore the number of growing roots continued to increase. Root exudation of organic matter increased. Secretion of oxygen enhanced. Combined with base fertilizer and tillering fertilizer was applied, which provided a wealth of nutrients and energy conditions for nitrifying bacteria. Nitrification was intense. Therefore nitrate nitrogen which nitrification produced was also up. Figure 2 could be a good description of it. Nitrate nitrogen provided rich substrates for the denitrification. So denitrification intensity was the highest in tillering. With the growth of rice, nitrification nutrient substrate reduced. Denitrification was also reduced. Plants gradually became aging. To maturity, denitrification intensity was the minimum. Measurement results showed that, in the cases of C soil denitrification intensity was the highest. At tillering, booting and maturity, denitrification intensity were 2.780, 2.273, NO 3 - -N mg kg-1 d-1. Throughout the experiment, an average of denitrification intensity was NO 3 - -N mg kg-1 d-1. While in the cases of G, denitrification intensity was the lowest. Average was only 52.34% of C. In the cases of C, J and G in the test group, denitrification intensity of maturity were only 54.2%, 5.72%, 2.18% denitrification intensity of tillering stage. These results suggest that the growth of rice itself has a certain effect on soil denitrification intensity. Denitrification intensity was the lowest in maturity. The reason was that soil nitrate nitrogen content was the higher in tillering (Figure 2). And with the growth of rice, soil nitrate nitrogen content was significantly decreased [9], which would further limit the denitrification enzyme activity,resulting denitrification intensity minimum in maturity. The study also found that under three different modes of water management control systems without plant denitrification intensity performed the same trend. Denitrification is a complex biochemical reactions involving nitrate reductase (Nar), nitrite reductase (Nir), etc. and is accompanied by electron transfer and energy production processes [10-13].Everything which affects denitrifying enzyme activity factors will affect the strength of denitrification. In the cases of C,test system maintained 3-5cm aqueous laye. The lower oxygen content within the system promoted exacerbate denitrification. Denitrification intensity always maintained a high level.in addition, increased soil moisture content will promote the rate of nutrients mineralization and improve the rate of utilization. Soil microbial activity rose and increased oxygen consumption, which making the soil system easy to form anaerobic area. Thereby it would affect the denitrification enzyme activity [13], which affects the intensity of denitrification. While in the cases of

3 586 Environmental Protection and Resources Exploitation II G, rice and non-plant system has low water content of soil pore. On one hand the lower moisture content may limit the amount and activity of the enzyme in soil [14].On the other hand, it increased the ability of soil pore exchange with the atmosphere, making the soil with greatly increased oxygen, thereby inhibiting denitrification process within the system, thus reducing the intensity of denitrification.in the cases of J, rice and control systems always maintained cm layer of water during rice in turn green to early tillering. Denitrification intensity in this stage was similar with the cases of C.From mid-tillering to maturity, the water in the system gradually dry off by the 5.0 cm water level and irrigated again to dry off, making the soil moisture in the system presented iterative process from wet to dry. Jian-gang Han [15,16] studies suggested that sediment moisture from the wet to dry process, nitrate reductase activity decreased rapidly, affecting denitrification strength.inferred by the results, along with changes in moisture content in the system, denitrification intensity showed repeatedly from high to low fluctuation trend. The study found that under three water managements, the average of rhizosphere soil denitrification intensity was greater than the average of no plant control system.the reason may be: plant rhizosphere is a special soil area.plant root exudates and root sheddings into the soil can increase the carbon source.while plant roots activity leads to aeration, moisture conditions and ph of the soil around the roots different with soil outside the root. So plant roots can improve denitrification [17].Therefore, the cultivation of rice soil denitrification intensity were higher than the control groups. Figure 1. Variation of soil denitrification intensity Figure 2. Variation of soil nitrate nitrogen content Conclusions Three kinds of water regimes on rice rhizosphere soil denitrification intensity has significant regulatory role, showing that: rice rhizosphere soil denitrification intensity was the highest in the cases of C, with an average of NO 3 - -N mg kg -1 d -1.While denitrification intensity was the lowest in the cases of G, with an average of only 52.34% of the case C. Denitrification intensity in the cases of J was between the two. With the growth of plants, denitrification intensity showed a downward trend under three water managements. To maturity denitrification intensity was the lowest. Denitrification intensity in the experimental group was higher than control group. Acknowledgements This work was financially supported by grants from Ministry of Education Key Laboratory of Modern Agricultural Equipment and Technology (no. NZ201010).

4 Advanced Materials Research Vols References [1] Kristiina Regina, Hannu Nyk?nen, JoukoSilvola,Pertti J. Martikainen.Fluxes of nitrous oxide from boreal peatlands as affected by peatland type, water table level and nitrification capacity.biogeochemistry,35(1996),p [2] Martikainen P J,Nykaken H C,Silvola P M. Effect of a lower water table on nitrous oxide fluxes from northern peatlands. Nature,366(1993),p [3] Zhi-Gao Sun, Jing-Shuang Liu, Ji-Song Yang, Xin-Hua Li, Wang-Ming Zhou Nitrification-denitrification and N2O emission of typical Calamagrostis angustifolia wetland soils in Sanjiang Plain. Chinese Journal of Applied Ecology, 18(1)(2007),p [4] Zhi-Gao Sun, Jing-Shuang Liu, Jun-Bao Yu, Hua-Peng Yi.Ammonia volatilization, nitrous oxide emission processes in wetland soil and affecting factors. Wetland science,18(1),(2008),p [5]Chen Zhigang,Chen Lei, Chen Hanxiang, et al. Denitrification enzyme activity in rice rhizosphere soil in response to water regulation[j].environmental Science&Technology,2014,37(5 ),p [6] Xiao-Juan Wang, Rong-She Zhang.Study on intensity of microorganism nitrification and denitrification in contructed wetlands. Acta Scientiae Circumstantiae, 26( 2)(2006),p [7] Shi-Dan Bao, et al. Analytical Methods of Soil and Agricultural Chemistry.Beijing : Agricultural Press, (2000),p [8] Yi-lin Li,Ya-li Zhang,Wei He, Qi-Rong Shen Comparison of growth and nitrogen uptake and assimilation by indica and japonica rice at the seedling stage under waterlogged conditions.journal of Nanjing Agricultural University,30 (3)(2007),p [9] Yi-lin Li,Ya-li Zhang,Jiang Hu, Qi-Rong Shen Spatiotemporal variations of nitrification in rhizosphere soil for two different rice cultivars at the seedling stage growing under waterlogged conditions. Acta Ecological Sinica,(2006),26 (5). [10] Li-Hua Liang,Jian-E Zuo.Review of modern culture-independent methods used to study community structure and function of denitrifying microorganisms. Acta Scientiae Circum Stantiae, 28(4)(2008),p [11] Li-Hua Liang,Jian-E Zuo.Denitrifying functional genes-the molecular marker for detection of denitrifying community structure. Microbiology,36(4)(2009),p [12] Xiang-Lan LI,Hua Xu,Zu-Cong Cai. Effect of water management on nitrous oxide emission from rice paddy field:a review. Soils,41(1)(2009),p [13] Ping-Ping Yu, Jin-Zhong Zhang, Cun-Gang Lin.Study progress on factors of influencing N2O emissions from agricultural soils. Environment and Sustainable Development,(5)(2006),p [14] Shu-Hui Huang, Jun Lu. Dynamic change of cracks and reductase activities in paddy fields. Journal of Soil and Water Conservation,18(1)(2004),p [15] Jian-Gang Han,Wei Zheng,Chun-Du Wu,Yong-Li Zhu. Response of nitrate reductase activity to alternation of drying and rewetting for sediment from a reed wetland. Environmental Science &Technology,34(5)(2011),p [16] Wei Zheng, Wei-Hong Huang, Jian-Gang Han.Denitrifying enzyme activities under alternation of drying and rewetting for wetland Sediments in Chongming East intertidal flat. Chinese Journal of Soil Science,44 (1)(2013),p [17] PHILIPPOT L,HALLIN S,BORJESSON G,et al.biochemical cycling in the rhizospere having an impact on global change. Plant and Soil,321( 1/2)(2009),p

5 Environmental Protection and Resources Exploitation II / Study on Denitrification Intensity in Rice Rhizosphere Soil under Water Management Model /