1 Agrifood Research Reports 121 2 Agrifood Research Reports 121 1 N i t r o g e n d y Nitrogen dynamics of organic n a m ic farming in a crop rotation based on s o f o red clover (Trifolium pratense) leys r g a n i c f a r Doctoral Dissertation m i n g i n Arja Nykänen a c r o p r o t a t i o n b a s e d o n r e d c l o v e r ( T r i f o l i u m p r a t e n s e ) l e y s Plant Production Agrifood Research Reports 121 60 pages, 4 appendices Nitrogen dynamics of organic farming in a crop rotation based on red clover (Trifolium pratense) leys Doctoral Dissertation Arja Nykänen Academic Dissertation To be presented, with the permission of the Faculty of Agriculture and Forestry of the University of Helsinki, for public criticism in Viikki, Auditorium B6, on April 25th,2008, at 12 o’clock noon. MTT Agrifood Research Finland Supervisor: Professor Artur Granstedt (Biodynamic Research Institute, Sweden) Reviewers: Professor Kerstin Huss-Danell (Swedish University of Agricultural Sciences) Docent Jouko Kleemola (Kemira Grow-How Ltd.) Opponent: Professor Friedhelm Taube (University of Kiel, Germany) Custos: Professor Markku Yli-Halla (University of Finland, Finland) ISBN 978-952-487-169-3 (Printed version) ISBN 978-952-487-170-9 (Electronic version) ISSN 1458-5073 (Printed version) ISSN 1458-5081 (Electronic version) http://www.mtt.fi/met/pdf/met121.pdf Copyright MTT Agrifood Research Finland Arja Nykänen Distribution and sale MTT Agrifood Research Finland, Information Management FI-31600 Jokioinen, Finland, phone + 358 3 4188 2327, e-mail [email protected] Printing year 2008 Cover picture Arja Nykänen Printing house Tampereen Yliopistopaino - Juvenes Print Oy Nitrogen dynamics of organic farming in a crop rotation based on red clover (Trifolium pratense) leys Arja Nykänen MTT Agrifood Research Finland, Plant Production Research, Lönnrotinkatu 3, 50100 Mikkeli, Finland, e-mail: [email protected] Abstract In agricultural systems which rely on organic sources of nitrogen (N), of which the primary source is biological N fixation (BNF), it is extremely important to use N as efficiently as possible with minimal losses to the environment. The amount of N through BNF should be maximised and the availability of the re- sidual N after legumes should be synchronised to the subsequent plant needs in the crop rotation. Six field experiments in three locations in Finland were con- ducted in 1994-2006 to determine the productivity and amount of BNF in red clover-grass leys of different ages. The residual effects of the leys for subse- quent cereals as well as the N leaching risk were studied by field measurements and by simulation using the CoupModel. N use efficiency (NUE) and N bal- ances were also calculated. The yields of red clover-grass leys were highest in the two-year-old leys (6 700 kg ha-1) under study, but the differences between 2- and 3-year old leys were not high in most cases. BNF (90 kg ha-1 in harvest- ed biomass) correlated strongly with red clover dry matter yield, as the propor- tion of red clover N derived from the atmosphere (> 85%) was high in our con- ditions of organically farmed field with low soil mineral N. A red clover con- tent of over 40% in dry matter is targeted to avoid negative N-balances and to gain N for the subsequent crop. Surprisingly, the leys had no significant effect on the yields and N uptake of the two subsequent cereals (winter rye or spring wheat, followed by spring oats). On the other hand, yield and C:N of leys, as well as BNF-N and total-N incorporated into the soil influenced on subsequent cereal yields. NUE of cereals from incorporated ley crop residues was rather high, varying from 30% to 80% (mean 48%). The mineral N content of soil in the profile of 0-90 cm was low, mainly 15-30 kg ha-1. Simulation of N dynamics by CoupModel functioned satisfactorily and is considered a useful tool to esti- mate N flows in cropping systems relying on organic N sources. Understanding the long-term influence of cultivation history and soil properties on N dynam- ics remains to be a challenge to further research. Key words: biological nitrogen fixation, mineral nitrogen, modelling, nitrogen use efficiency Puna-apilanurmiin perustuvan viljelykierron typpitalous luonnonmukaisessa viljelyssä Arja Nykänen MTT, Kasvintuotannon tutkimus, Lönnrotinkatu 3, 50100 Mikkeli, e-mail: [email protected] Tiivistelmä Luonnonmukaisessa viljelyssä, jossa typen (N) lähteenä käytetään vain biolo- gisen typensidonnan (BNF) kautta saatua orgaaniseen ainekseen sitoutunutta typpeä, on erityisen tärkeää käyttää typpi mahdollisimman tehokkaasti mini- moiden hävikit ympäristöön. Tällaisissa viljelytavoissa BNF tulisi maksimoi- da ja palkokasvien jälkeen maahan jäävän typen saatavuus tulisi sovittaa vilje- lykierron seuraavien kasvien tarpeisiin sekä ajallisesti että määrällisesti. Tut- kimuksessa tehtiin yhteensä kuusi kenttäkoetta kolmella paikkakunnalla Suo- messa vuosina 1994 – 2006. Tavoitteena oli selvittää luonnonmukaisesti viljel- tyjen eri-ikäisten säilörehuksi korjattujen puna-apila-heinänurmien sadontuotto ja BNF. Nurmien jälkivaikutusta seuraaville kahdelle viljalle kuten myös typen huuhtoutumisriskiä selvitettiin kenttäkoemittauksilla sekä CoupModel tietoko- nesimuloinnin avulla. Typenkäytön tehokkuutta (NUE) ja typpitaseita lasket- tiin myös. Tutkitut puna-apila-heinänurmet tuottivat keskimäärin korkeimmat sadot 2-vuotisina (6 700 kg ha-1), mutta ero 3-vuotisiin nurmiin oli pieni. BNF (90 kg ha-1) korreloi voimakkaasti apilan kuiva-ainesadon kanssa, kun apilan typestä suurin osa (> 85 %) oli peräisin ilmakehästä ja maan liukoisen typen määrä oli alhainen. Nurmiviljelyssä, jossa nurmisato korjataan pois, pitäisi nur- men apilapitoisuuden olla yli 40 % kuiva-aineesta, jotta nurmen typpitase oli- si positiivinen ja typpeä jäisi seuraavan kasvin käyttöön. Tutkittujen nurmien peltoon jättämä typen ylijääm oli pieni, mikä selittänee nurmen alhaista jälki- vaikutusta seuraavien viljojen satoon ja typen ottoon. Toisaalta nurmisadot ja niiden C:N, kuten myös nurmesta maahan muokattu typpi- ja BNF -määrä vai- kuttivat viljasatoihin. Viljojen NUE oli kohtalaisen korkea, 30 % - 80 % (keski- määrin 48 %), kun se laskettiin nurmien maahan muokatun typen perusteella. Maan liukoisen typen pitoisuus koko maaprofiilissa (0 - 90 cm) oli matala, pää- osin 15 - 30 kg ha-1. Tietokonesimulointi CoupModel -ohjelmalla onnistui koh- talaisen hyvin ja se vaikuttaakin lupaavalta jatkokehittelyyn käytettäväksi luo- muviljelyssä. Lisätutkimusta tarvitaan selvittämään viljelyhistorian ja maape- rätekijöiden vaikutusta luomutuotannon typpitalouteen koko viljelykierrossa. Avainsanat: biologinen typensidonta, maan liukoinen typpi, mallintaminen, ty- pen käytön tehokkuus 4 Foreword The research projects presented here were conducted at the MTT Agrifood Re- search Finland during 1996-2006. The field experiments were carried out in the research stations of MTT in Juva, Mietoinen and Sotkamo. I wish to express my sincere thanks and deep gratitude to Professor Markku Yli- Halla for guiding me through this demanding process. Your endless work by commenting my text made it possible to achieve all the goals I had in my mind. I am grateful for my supervisor Professor Artur Granstedt, who initiated most of the experiments and encouraged me with all my research work in the begin- ning of my career as a researcher. You have given me your support also during the difficult years of my life. I appreciate Professor Antti Jaakkola for his encou- ragement and initiation of my studies to be a PhD. My warmest thanks to all my co-authors in the articles of this thesis: M.Sc. Su- sanna Kunttu, M.Sc. Antti Laine and Mr. Jukka Kemppainen. Especially I wish to thank M.Sc. Lauri Jauhiainen for being so patient with me and doing the sta- tistical analyses whenever I needed them. I also thank Dr. Tapio Salo for giving his valuable input on the modelling without any ‘project’ for that. I am so grate- ful for Dr. Kristina Lindström for her support and discussions during our trips in China, as well as for the guidance in scientific writing. I am thankful to the reviewers of this thesis, Professor Kerstin Huss-Danell and Docent Jouko Klee- mola, for their useful comments and suggestions for improving the manuscript. I am grateful to all the people, who conducted the field and laboratory work. Es- pecially I thank Mr. Kari Narinen and Ms. Marja Harmoinen for their valuable work in the fields of Partala and the endless sorting of clovers, grasses and weeds. I thank also Ms. Päivi Hämäläinen and Mr. Lauri Kössö in Juva as well as Ms. Marja Kujala and Mr. Reijo Björkbacka in Mietoinen. I wish to thank Ms. Riit- ta Koistinen and Ms. Ritva Kalakoski for always finding me the right articles in a short time. I acknowledge Sevastiana Ruusamo and Mary Mezler for the lin- guistic revision of my thesis. This work was initially supported by MTT Agrifood research Finland and I wish to express my sincere thanks to Dr. Pirjo Dalman, Prof. Sirpa Kurppa, Dr. Aar- ne Kurppa and M.Sc. Harri Huhta. The financial support of the Ministry of Ag- riculture and Forestry of Finland, guided by Lic.Sc. Markku Järvenpää, is great- ly acknowledged. Additional support for the writing of this thesis belong to the Agricultural Research Foundation of August Johannes and Aino Tiura and the Finnish Cultural Foundation. Finally, I owe my dearest thanks to my children Paula, Paavo and Pekka for li- ving their lives as children do, and ignoring me when loosing my nerves. I thank my mother and father as well as my brother Jouko and my former husband Arto for taking care of the children during the critical times of writing. My warmest thanks to my sister Pirjo and all my friends for being so supporting and encou- raging during this project. 5 List of original articles The thesis is a summary and discussion of the following articles, which are re- ferred to by their Roman numerals in the text: I Nykänen, A., Granstedt, A., Laine, A. & Kunttu, S. 2000. Yields and clo- ver contents of leys of different ages in organic farming in Finland. Bio- logical Agriculture and Horticulture 18: 55-66. II Nykänen, A., Jauhiainen. L., Kemppainen, J. & Lindström, K. 2008. Field-scale spatial variation in soil nutrients and in yields and nitrogen fixation of clover-grass leys. Agricultural and Food Science. Submitted. III Nykänen, A., Granstedt, A., Laine, A. & Jauhiainen, L. 2008. Residual effect of clover-rich leys on soil nitrogen and successive grain crops. Ag- ricultural and Food Science. In press. IV Nykänen, A., Salo, T. & Granstedt, A. 2008. Simulated cereal nitrogen uptake and soil mineral nitrogen after clover-grass leys. Nutrient Cycling in Agroecosystems. Submitted. The author’s contrbution in joint publications I, III, IV Arja Nykänen planned and conducted the field experiments together with Artur Granstedt, and calculated the results including the correlation analysis in Paper III. She also participated in the management of the field experiments in Juva. Arja Nykänen was mainly responsible for interpret- ing the results and for writing the papers. II Arja Nykänen planned and conducted the field experiments and calculat- ed and interpreted their results. She also participated in the management of the field experiment in Juva. Arja Nykänen was mainly responsible for writing the paper. Reprints of the original articles are published with the kind permissions of A B Academic Publishers (I) and The Scientific Agricultural Society of Fin- land (III). 6 Abbreviations BNF: biological nitrogen fixation BNF-N: N originated from BNF, for example in incorporated biomass DM: dry matter N: nitrogen Ndfa: proportion of clover N derived from air NH +-N: ammonium-N 4 NO --N: nitrate-N 3 N : total N content tot NUE: N use efficiency OM: organic matter PCA: Principle component analyses PC: Principle component 7 Contents 1 Introduction .........................................................................................9 1.1 Organic farming in Finland .................................................................9 1.2 Red clover in leys ..............................................................................10 1.3 Biological nitrogen fixation .............................................................11 1.4 Nitrogen cycling and processes in soil ..............................................13 1.5 Crop rotation and the problem of nitrogen in organic farming ........15 1.6 Objectives of the study ......................................................................18 2 Materials and methods ..............................................................................19 2.1 Experimental sites .............................................................................19 2.2 Field experiments ..............................................................................21 2.3 Methods of analyses and measurements ...........................................23 2.4 Calculated parameters .......................................................................24 2.5 Description of the CoupModel ..........................................................25 2.6 Statistical analyses ............................................................................26 3 Results .......................................................................................................28 3.1 Nitrogen input from red clover based leys ........................................28 3.1.1 Ley yields and red clover contents ......................................28 3.1.2 Biological nitrogen fixation .................................................33 3.1.3 Incorporated material - nitrogen content and C:N ...............35 3.2 Nitrogen output from red clover based leys ......................................36 3.2.1 Cereal yields and nitrogen uptake ........................................36 3.2.2 Nitrogen in soil and leaching risk ........................................38 3.3 Nitrogen balance in crop rotation .....................................................39 3.3.1 Nitrogen input-output-ratio ..................................................39 3.3.2 Nitrogen use efficiency ........................................................40 3.3.3 Simulation as a tool for describing N dynamics ..................41 4 General discussion ....................................................................................43 5 Conclusions ...............................................................................................45 6 References .................................................................................................46 7 Appendices................................................................................................61 8 1 Introduction 1.1 Organic farming in Finland According to the International Federation of Organic Agriculture Movements (IFOAM), organic agriculture consists of four principles: the principles of Health, Ecology, Fairness and Care (IFOAM 2005). Organic food and farming aims to minimise the use of external inputs and it favours renewable resourc- es and recycling. Organic farming respects the environment’s own systems for controlling weeds, pests and disease by avoiding the use of synthetic pesticides, herbicides, chemical fertilisers, growth hormones, antibiotics and gene manip- ulation. Instead, organic farmers use a range of techniques that help sustain ec- osystems and reduce pollution. Soil fertility is maintained and enhanced by a system, which optimises soil biological activity as the means to provide nutri- ents for plants and animals as well as to conserve soil resources. Animal hus- bandry is regulated with particular concern for animal welfare and by using natural foodstuffs. Currently in all the EU countries regulation 1804/1999 and supplementing reg- ulation 2092/91 on organic production provide a minimum standard concern- ing the right to label food as organic (CEC 1999). In Finland, state authorities carry out the inspection and certification of organic production. Biochemist Professor A.I. Virtanen can be considered the pioneer of organic farming in Finland. During the 1930s, Virtanen developed the AIV-System, a N self-sufficient cultivation method, which included crop rotation with pastures, bread grains and also intensive red clover leys for winter-feeding preserved as silage. Silage was made by a new method using mineral acids for preservation. Professor Virtanen was awarded the Nobel Prize for chemistry in 1945 for this method, on which silage making in northern conditions is still based. Profes- sor Virtanen was also known as a researcher of BNF (Karström and Virtanen 1937, Virtanen 1938, Virtanen 1944). Organic farming began in Finland as early as 1910, and the first farm was start- ed in 1927. Organic acreage was very small until the early 1990s, when the Ministry of Agriculture and Forestry first started subsidizing farmers for con- version to organic farming. Even more farms started to convert in 1995, when Finland joined the EU. The highest number of farms and the greatest cultivat- ed area was reached in 2004, with 4 900 farms (6.6%) and 162 000 hectares (7.3%), respectively. Today, 6.6% of Finnish arable area is certified as organic, which totals 149 500 hectares and 3 900 farms. The average size of an organ- ic farm is 38 hectares, which is thus larger than the average size of all farms in Finland. About 50% of the total organic arable area was under ley cultivation and almost 35% was under cereals. About 45% of the organic farms practice animal production (Evira 2007). 9