JOURNALOF InternationalScientificPublications: EcologyƬSafety,Volume6,Partʹ Peer-ReviewedOpenAccessJournals Publishedat: http://www.science-journals.eu PublishedbyInfoInvestLtd www.sciencebg.net ISSN1313-2563,2012,EuropeanUnion JournalofInternationalScientificPublications: EcologyƬSafety,Volume6,Partʹ ISSN1313-2563,Publishedat:http://www.science-journals.eu EditorinChief IoannisTakos,Greece Co-EditorinChief CengizKurtulus,Turkey ExecutiveSecretary MarinaSizemskaya,Russia EditorialBoardMembers AlexyDanchev,Turkey BrankoMarinkovi©ǡSerbia DimiterSyrakov,Bulgaria DimitriosBakaloudis,Greece DanielBucur,Romania GalatsidasSpyridon,Greece HamidAbbasdokht,Iran IjazNoorka,Pakistan LjubicaKomazec,Serbia JuyingJiao,China JovanCrnobarac,Serbia LevRuzer,USA MuhammadAfzal,Pakistan MeenuVikram,USA NadezhdaKhristoforova,Russia OanaZamfirescu,Romania OlegRomanovskii,Russia TheodoraMerou,Greece TatianaTolstikova,Russia VladimirSolodukhin,Kazakhstan 2 PublishedbyInfoInvest,Bulgaria,www.sciencebg.net JournalofInternationalScientificPublications: EcologyƬSafety,Volume6,Partʹ ISSN1313-2563,Publishedat:http://www.science-journals.eu PublishedinAssociationwithScienceƬEducationFoundation. AnypapersubmittedtotheJournalofInternationalScientificPublications: EcologyƬSafetyǦshouldNOTbeunderconsiderationforpublicationatanother journal.Allsubmittedpapersmustalsorepresentoriginalwork,andshouldfully referenceanddescribeallpriorworkonthesamesubjectandcomparethe submittedpapertothatwork. Allresearcharticlesinthisjournalhaveundergonerigorouspeerreview,based oninitialeditorscreeningandanonymizedrefereeingbyatleasttworeferees. Recommendingthearticlesforpublishing,thereviewersconfirmthatintheir opinionthesubmittedarticlecontainsimportantornewscientificresults. Theauthorsofthearticlesbeartheresponsibilityfortheircontent. Whenquotingthearticlestheirauthorandeditionshouldbementioned. Itisnotallowedtheeditionofthescientificarticlestobecopied,multipliedand distributedwiththepurposeoftradewithoutthepermissionoftheeditor. 3 PublishedbyInfoInvest,Bulgaria,www.sciencebg.net JournalofInternationalScientificPublications: EcologyƬSafety,Volume6,Partʹ ISSN1313-2563,Publishedat:http://www.science-journals.eu VARIOUS FLUXES OF CARBON (C) AND NITROGEN (N) UNDER CONVENTIONAL AND NO-TILLAGE MANAGEMENT PRACTICES: A MODELLING STUDY AT SELECTED SITE IN THE SLOVAK REPUBLIC Jan Horak1, Zuzana Lehocka2, Stefan Zak2, Karol Kovac3, Dusan Igaz1 and Jan Cimo1 1Department of Biometeorology and Hydrology, Slovak University of Agriculture in Nitra, Hospodarska 7, Nitra 94901, Slovakia 2Research Institute of Plant Production, Bratislavska cesta 122, Piestany 92168, Slovakia 3Agrogenofond n.o., Mala podhajska 2323/9, Nitra 94901, Slovakia Abstract This paper describes and quantifies effects of conversion of conventional tillage system (CT) to no-till system (NT) on various fluxes of carbon (C) and nitrogen (N) in agro-ecosystem. The process-based model DNDC was used in this study to quantify these effects. The study was carried out at a selected experimental station of the Research Institute of Plant Production (RIPP) in the maize growing region in the Slovak Republic during the period of 1999-2004. Modeling results showed that the conversion of CT to NT system (1) increased soil organic carbon (SOC) content on average by 14%, and switched the SOC balance from a net loss to a net sink; (2) decreased soil CO2 emission on average by 12%; (3) had little impact on N2O emissions; (4) decreased NO emission on average by 9%; (5) increased - N2 production by 11%; (6) decreased NO3 leaching by 9%; (7) and had impact on the quality of soil organic matter. Key words: DNDC model, conventional tillage, no-till, carbon, nitrogen, agro-ecosystem 1. INTRODUCTION Conventional tillage (CT) system as a traditional farming management has its advantages and disadvantages. For example advantages of this system is, that soil nutrients are more intensively used by crops, which compensate the costs of expensive mineral fertilizers. CT system completely inverts the soil and has the positive effect on weediness. However there is a growing trend for a conversion of CT system to conservation tillage systems including reduced till (RT) and no-till (NT) systems. It is mainly influenced by higher production cost under CT system and also by soil-ecological conditions. CT system on agricultural land has influence on soil quality and soil moisture. Continuous use of CT system can increase the depletion of soil organic matter and cause soil erosion (Hussain et al., 1999). Intensive soil tillage increase decomposition of soil organic matter and release nutrients from soil. If the soil organic matter inputs into the soil are not adequate to mineralization, the amount of humus continuously decreases (Kovac et al., 2007). The main reason for implementation of conservation tillage systems, including NT system is because they have shown potential for soil conservation and potential for saving their properties. They are more water efficient (Lindwall and Anderson 1981), reduce soil erosion (Hussain et al., 1999) and reduce production costs due to lower fuel and labor inputs. Conversion from CT system to NT system also changes carbon (C) and nitrogen (N) fluxes which move through agro-ecosystem in couple biogeochemical cycles. C and N have been adopted by most life forms on Earth as the basic material for construction and metabolism. As green plants grow by assimilating CO2, they require N to form amino acids and other essential compounds (Lacher, 1995; 4 PublishedbyInfoInvest,Bulgaria,www.sciencebg.net JournalofInternationalScientificPublications: EcologyƬSafety,Volume6,Partʹ ISSN1313-2563,Publishedat:http://www.science-journals.eu cit. in Li et al., 2005). As plant tissue are incorporated into the soil after the plants die, decomposers decouple C and N as they derive energy from the breakdown of the organic compounds, ultimately re- + - mineralizing most C and N to CO2 and inorganic N (e.g., NH4 or NO3 ). The energy required by the soil microbes is usually generated by oxidation-reduction reactions, transferring electrons from the C atoms existing in the organic compound to oxygen. If oxygen is unavailable, some microbes (e.g., denitrificants) can use other oxidants as electron acceptors. After oxygen, the most ready-reduced - oxidant is nitrate (NO3 ), and this denitrification process generates nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2) (Conrad, 1996; cit. in Li et al., 2005). N2O is also produced during nitrification, the microbially-mediated oxidation of ammonium to nitrate. Soils under NT system have lover mineralization of soil organic matter. Conservational systems have - been widely discussed for their potential to reduce nitrate (NO3 ) leaching through improving soil water and SOC content storage (Dinnes, 2004). Modeling results showed that under no-till conditions, reduction in the N mineralization rate directly resulted in increased SOC accumulation and less inorganic N available for crop uptake and leaching (Farahbakhshazad et al., 2007). Several studies showed that this conversion could have a favorable impact on atmospheric concentrations of greenhouse gas namely carbon dioxide (CO2) by increasing sequestration of soil carbon (C) (Kern and Johnson, 1993; Lal et al., 1998; West and Post, 2002,). However several field and modeling studies showed different statements on nitrous oxide (N2O) emissions under NT system. For example some studies reported that N2O fluxes can be greater under NT system as compared to CT system (Baggs et al., 2003; MacKenzie et al., 1997; Linn and Doran, 1984; Palma et al., 1997; Mummey et al., 1998; Goodroad et al., 1984; Aulakh et al., 1984). Other studies show similar values of N2O fluxes under both CT and NT systems (Kessavalou et al., 1998; Robertson et al., 2000; Parkin and Kaspar, 2006). On the other hand Jacinthe and Dick, 1997 reported higher N2O emissions under CT system as compared to NT system. Modeling assessment of N2O fluxes from 44 CT systems vs. NT systems comparison found, that for their humid climate classification (dominated by sites in the U.S. Corn Belt), the changes in N2O flux as a result of converting tilled systems to no-till changed over time (Six et al., 2004 cit. in Parking and Kaspar, 2006). They estimated that 5 years after the establishment of NT system, N2O were higher than CT. After 10 years under NT system, N2O emissions were reduced relative to CT. However, by year 20, N2O from NT system were lower than in a CT system. There is also effect of conversion CT to NT system on emissions of nitric oxide (NO) gas. Soil NO emissions can significantly affect tropospheric ozone (O3) production. Ozone is an important greenhouse gas. There are very few studies regarding tillage effects simultaneously with the effect of fertilizer management, which can influence NO and also N2O emissions (Mosier et al., 1998; Veldkamp and Keller, 1997). There is also study considering further reduction of N2O to dinitrogen (N2) because of higher WFPS under NT system in the overlying 0 to 10cm zone, thereby promoting the reduction of N2O to N2 during transport toward the soil surface (Linn and Doran, 1984b). Sahrawat and Keeney (1986) also noted that continuously wet soils made denitrification proceeds rapidly to N2. Implementation of conservation systems including reduced tillage and no-till systems is also an indirect measure resulting from ecological standards of the European Union for securing good agricultural and environmental conditions (GAEC) (ecological