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Ali Coşkan, Mustafa Gök, Kemal Doğan University of Çukurova, Faculty of Agriculture, Department of Soil Science, Adana, Turkey Abstract A laboratory experiment was carried out to determine the denitrification capacity of the Doğancı, Geçitkale, Akdeniz, Balıkesir, Pamuklu, Zümrütköy and Türkmenköy that are widely distributed soil series of Turkish Republic of Northern Cyprus. Soils are placed in anaerobic jars (20% initial O2, 80% He) with addition of 300 mg kg-1 NO-3-N. Produced gases (CO2, N2 and N2O) along with O2 consumption were determined by gas chromatography. Moreover, ammonium and nitrate concentration of the soils were measured at regular intervals. The measured O2 consumption and CO2 production values as parameters of biological activities, revealed considerable differences among the soil series studied. The more rapid O2 consumption and the higher CO2 production were determined in Balıkesir, Zümrütköy and Türkmenköy soil series. Furthermore, O2 level in the anaerobic jar was immediately dropped in early measurement intervals and was about 0% at the end of the last measurement, particularly above mentioned soil series. The Zümrütköy soil series has higher CO2 production in all measurement periods than the others and reached 975 ?g CO2 g dry soil-1, at the end of experiment where others vary from 257 to 745.The measurements of N2O and N2 gases revealed that the most of the denitrification product consists of N2. Additionally, the highest N2O and N2 productions were determined in the Balıkesir series with 251 ?g N2O-N g dry soil-1 and 498 ?g N2-N g dry soil-1. When all series compared, there were significant differences for the production of N2 and N2O production. Nitrate and ammonium analyses measured in relation to time, ammonium content was similar in all series, however, nitrate content significantly decreased according to the measurement period. Introduction Efficient use of nitrogen fertilizer requires well understanding of nitrogen dynamics in the soil. Due to the many loss pathways, applied nitrogen fertilizer did not effectively used by plants. One of the major nitrogen losses progress, denitrification results economical and environmental impacts. The denitrification products, nitrous oxides, are effective as a "green house" and contribute to the formulation of tropospheric ozone (Barrow, 1994; Gök, 1988). Denitrification, therefore, occurs in many soil conditions, stimulated by nitrate and water contents of soil, temperature and insufficient oxygen diffusion (Gök et al., 1999; Boşgelmez et. al., 2001). The nitrogen fertilizers could easily convert to nitrate due to the nitrification progress and thus, denitrification would be triggered even in the case of utilization of ammonium as a nitrogen source. Fertilization with high levels of N (300 kg of N ha-1) positively affected on the occurrence and amounts of the diazotrophic bacteria (Junior et. al, 2000). Low N use efficiency and high nitrate pollution potentials are the major problems in intensive agricultural production systems. Losses the denitrification in suitable condition accounted for ~25% of the applied nitrogen (Jackson et. al., 1994). Freney et. al. (1992) reported that, the use of an inhibitor for limiting nitrification, prevents nitrogen loss by denitrification, increases grain N and resulted in a 46% greater recovery of applied nitrogen in the plant-soil system at harvest.The aim of the research was to determine the denitrification capacity of widely distributed TRNC soils. Material and Methods Some of physical and chemical properties of the sub soils (0-20 cm) of selected soil series were given in Table 1.  The selected soil samples were placed into anaerobic jars as soon as set to field capacity and enriched by 300 mg NO3--N kg-1 dry soil-1. The atmosphere of the jar was adjusted for 20% oxygen and 80% helium (v/v). Samples incubated at 30 OC for 55 days. The atmosphere of the jar was analyzed by gas chromatography (Hewlett Packard GC 5890) equipped with ECD (Electron Capture Detector) and TCD (Thermal Conductivity Detector). The gases of CO2 and O2 were measured using TCD (200 OC detector, 54 OC oven and 60 oC injector temperatures) whereas N2 and N2O were measured by ECD (300 oC detector, 54 OC oven and 60 OC injector temperatures) (Benckiser, 1995). One parallel of the jars quashed on every other sampling day and the soils were analyzed for their nitrate (Fabig et. al., 1978) and ammonium (Deutsche Einheitsverfahren, 1983) contents. Results Oxygen Consumption and CO2, N2, N2O Fluxes The effects of 55-day incubation on the gases of O2, CO2, N2 and N2O for the soil series of Doğancı, eçitkale, Akdeniz, Balıkesir, Pamuklu, Zümrütköy, Türkmenköy were given in Figure 1a and 1b.   Results revealed that, the initial 20% oxygen was reduced in all soil series as a function of time. Therefore, in Balıkesir, Zümrütköy and Türkmenköy, oxygen consumption was significantly higher (P=0.05) than the other series. The measured oxygene percentage of Türkmenköy and Zümrütköy were decreased considerable in 13th measurement day and reached 0% in Türkmenköy on 41st day whereas Zümrütköy on 48th. In the last measurement, oxygen percentage of the series of Doğancı, Geçitkale, Akdeniz and Pamuklu were 7.5%, 6.6%, 5.8% and 6.2%, respectively. The CO2 fluxes in Balıkesir, Türkmenköy and Zümrütköy were significantly higher than the others, in accordance with O2 consumption. Although, the measured CO2 fluxes in Doğancı Geçitkale, Akdeniz and Pamuklu were increased rapidly; it was not significant (P=0,05). The CO2 values on the last measurement were 257, 445, 510, 745, 347, 974 and 676 ?g CO2/g dry soil for Doğancı, Geçtikale, Akdeniz, Balıkesir, Pamuklu, Zümrütköy and Türkmenköy soil series, respectively. Results showed that the most of the denitrification products consisted N2. The highest N2 was measured in Balıkesir series (498 g N2-N g ds-1) where as the lowest was in 136 ?g N2-N g ds-1in Turkmenköy. The lowest N2O-N values were 0.7 and 0.4 ?g N2-N g ds-1 in the Doğancı and Türkmenköy respectively while the highest value was in Balıkesir (251 g N2-N g ds-1). The highest denitrification losses (N2+N2O) were determined in Balıkesir (749 g N g ds-1) whereas the lowest were 137 g N g ds-1 in Türkmenköy. Nitrate and Ammonium Occurrence One parallel of the jars was quashed every other sampling day and the soils were analyzed for nitrate and ammonium contents. The effects of 55-day incubation on the nitrate and ammonium contents of soils were given in Table 2 and Table 3, respectively.   The soil nitrate contents were reduced as function of time in accordance with denitrification losses (N2 and N2O). In the Geçitkale, Akdeniz and Zümrütköy, the increments were significantly higher (P=0.05). Ammonium contents showed relatively lower values than the nitrate contents due to the enrichment by nitrate-N in the beginning of experiment. Conclusion The incubation study for the determination of the denitrification potentials of the widely distributed soil series of the Turkish Republic of Northern Cyprus (TRNC) related that soils with similar mineral N contents prior the incubation, the N losses (N2-N+N2O-N) following NO-3-N fertilization were significantly differing from each other. CO2 production and O2 consumption also showed significant flux differences related both to amount and time. Moreover, great amounts of denitrification losses occurred with the presence molecular O2. Significant differences both in denitrification and biological activity parameters should be most probably due to varying of soil properties, which also affected the biological properties as well. Abou Seada and Ottow (1988) suggested that denitrification losses are more closely related to waters soluble organic matter than the total organic matter content of the soil. Additionally, the presences of O2 along with mineralizable organic matter content are also important factors for the denitrification losses (Gök and Ottow, 1988). Results revealed that the determinations of present and potential denitrification losses are very important factors for fertilizer consumption and environmental pollution (degradation of ozone layer!). References . Abou Seada and M.N.I., Ottow, J.C.G., 1988. Einfluss chemischer Bodeneigenschaften auf Ausmass und Zusammensetzung der Denitrifikationsverluste drei verschiedener Bakterien. Z. Pflanzenernaehr. Bodenkd. 151: 109-115. . Barrow, C. J., 1994. Land degradation through global pollution: "the greenhouse effect", In: Land Degradation. Cambridge University Press. 196., p:31-47, Cambridge. . Benckiser, G., H.J. Lorch, J.C.G. Ottow, 1995. Quantification of Total Denitrification Losses from Undisturbed Field Soils by the Acetylene Inhibition Technique. In: Methods in Applied Soil Microbiology and Biochemistry ISBN 0-12-513840-7. Chapter 10. p 473-478. . Boşgelmez, A., Boşgelmez, İ. İ., Savaşçı, S., Paslı, N., 2001. Ecology-II (Soil) ISBN 975-96377-2-3. Ankara. . Deutsche Einheitsverfahren Zur Wasser-Abwasser Und Schlammuntersuchungen, (1983). Fachgruppe Wasserchemie in der Gesellschaft Deutscher Chemiker (ed.) Verlag Chemie, Weinheim / Bergstrasse (BRD). . Fabig, W., Ottow, J.C.G., Müller, F. (1978). Mineralization von 14C-markiertem Benzoat mit Nitrat als Wasserstoff-akseptor unter vollstaending anaeroben Bedingungen sowie bei vermindertem Saurstoffpartialdruck. Landwirtsch. Forsch. 35, 441-453. . Freney, J.R., Smith, C.J., Mosier, A.R., 1992. Effect of a new nitrification inhibitor (wax coated calcium carbide) on transformations and recovery of fertilizer nitrogen by irrigated wheat, Fertilizer Research, 32:1-11. . Gök, M., 1988. The Role of Soil Microorganisms on the Occurrence of Ozone Destructive Gases (N2O and NO). Conference on Fifth Scientific and Technical Environment Adana S: 452-463. (in Turkish) . Gök, M., Coşkan, A., Onaç, I., Sağlamtimur, T., Tansı, V., Karip, B., İnal, İ., 1999. The Effects of Organic Fertilization on N-Mineralization, N-loss by Denitrification and Microbial Activity. The 1st Conference on Agriculture in GAP (Southern Anatolia). 2nd Volume. T.C. University of Harran. Faculty of Agriculture. 26-28 May, Şanlıurfa. P 971-978. (in Turkish) . Gök, M., Ottow, J.C.G., 1988. Effect of Cellulose and Straw Incorporation in Soil on Total Denitrification and Nitrogen Immobilization at Initially Aerobic and Permanent Anaerobic Conditions. Biol. Fertil. Soils 5, 317-322. . Jackson, L.E., Stivers, L.J., Warden, B.T., Tanji, K.K., 1994. Crop nitrogen utilization and soil nitrate loss in a lettuce field, Fertilizer Research, 37:93-105. . Junior, F.B.R, Reis, V.M., Urquiaga, S., Döbereiner, J., 2000. Influence of nitrogen fertilization on the population of the population of diazotrophic bacteria Herbasprillum spp. and Azotobacter diazotrophicus in sugar cane (Saccharum spp.), Plant and Soil, 219:153-159. Acknowledgement We thank to Assoc. Prof. Dr. Erhan AKÇA at the University of Çukurova Faculty of Agriculture, Department of Soil Science, Adana-Turkey. |