THE USE OF DAIRY MANURE COMPOST FOR SUSTAINABLE MAIZE (Zea mays L.) PRODUCTION Vânia Cabüs de Toledo Thesis submitted to the University of London in partial fulfilment of the requirements for the Degree of Doctor of Philosophy Wye College University of London September 1996 7 BIBL\ t Lc4oI() Abstract Intensive production systems for maize (Zea mays L.) based on the use of inorganic fertilisers are expensive and unsustainable, as their production is dependent on fossil fuels. Additionally, inorganic fertilisers are unable to maintain soil fertility over the long-term, and are related to environmental problems such as soil erosion and nitrate pollution of the ground water table. Moreover, high cost agrochemicals are either unavailable or too costly for small farmers in tropical countries, where maize is usually grown as a subsistence crop. This research project examined the use of compost derived from dairy manure and cereal straw, renewable resources available on the farm, as an organic fertiliser for a sustainable maize production system. The effects of this compost on soil and plant nutrient content, and on maize and weed growth were studied, examining the various soil-plant interactions. The relevant literature was reviewed, comparing different production systems, and examining aspects of maize production, nutrient recycling and the effects and interactions of compost in the soil-plant system. Field and glasshouse experiments were carried out from 1993 to 1995 on Wye College Estate, UK, comparing the use of dairy manure compost and inorganic fertiliser in forage maize production. Soil chemical (nutrient content) and biological (microbial biomass and activity) aspects were analysed at several stages of maize development. Plant (maize and weed) nutrient content and biomass production were also determined. A laboratory experiment studied nitrogen mineralisation rates of dairy manure compost under controlled conditions. A further field experiment, conducted by the Llniversità degli Studi della Tuscia in Viterbo, Italy, allowed comparisons of some results under different climatic conditions. There was evidence that compost application could adequately supply maize nutrient requirements, by enhancing and sustaining soil fertility, with increased microbial biomass and nutrient levels. In general, maize biomass production was similar under both compost and chemical fertiliser addition, but a potential for higher maize dry matter yields with long-term compost application was suggested. In addition, compost was consistently associated with a lower potential for nitrate pollution of the ground water table. 2 Acknowledgements This research project would not have been possible without the help and support received, which I gratefully acknowledge: Dr. Howard Lee and Dr. Trudy Watt, dedicated supervisors, and, above all, friends on whom I could count; Dr. Joe Lopez-Real, for the support with the Controlled Composting Systems Unit, the Microbiology Laboratory and the friendship; Sara Marinari, Dr. Luigi Badalucco and Prof. Stefano Grego, from the Department of Agrobiology and Agrochemistry in Università degli Studi della Tuscia (Viterbo, Italy), with whom I had the privilege to work; Sarah Brocklehurst and Trudi Krol, helping me with all those soil and plant samples in the Analytical Laboratory; Len Godden and Dan Barker, from the Agricultural Engineering Workshop, the two pairs of hands that made the hard work in the field experiments possible, and John Sharp, for keeping all the machinery working; Roger Stuart, from the NIAB office, not only lending equipment but also helping in the harvest; Pam Kite and the technicians in the glasshouse, assisting in all those experiments; Sian Phelps and all the library staff, always friendly and helpful; Jeff Brooks, for all the Audio-Visual support; Charles, Donald, Geoff, Joe, Andy, Dylan, Fred, Asun, Susie, Ruth, and all those who helped me at some stage with the practical work; all the friends in Wye, for the chats and the good moments. Special thanks to Lucienne Rasetti and Mario Rodrigues, dear friends who shared with me sweat, tears and laughs, in and outside maize experiments. A very special thank you to my partner Bill Martin, not only for helping me with those endless sample grindings on Sundays, but for being patient and for making me happy. This research project had the financial support of CAPES-Brazil. 3 To Rubens, Rosa and Valéria, father, mother and sister, whom I love and admire, and whose support throughout my life made this work possible. Table of Contents Abstract .2 Acknowledgements .3 Dedication...............................................................................................4 Tableof Contents ...................................................................................5 Listof Tables.........................................................................................12 Listof Figures .......................................................................................15 Listof Plates..........................................................................................18 Abbreviationsand Symbols ...............................................................19 chapter1. Introduction......................................................................20 1.1 General aspects .................................................................................................20 1.2 Objectives of this research...............................................................................21 1.3 Structure of thesis.............................................................................................23 Chapter2. Literature lei.rie',v............................................................25 2.1 Maize production..............................................................................................25 2.1.1 Climatic requirements.........................................................................25 2.1.2 Agronomic and physiological aspects...............................................26 2.1.3 Factors affecting maize productivity.................................................27 2.1.4 Nutrient requirements.........................................................................28 2.2 Historical background of production systems.............................................30 2.2.1 From organic to chemical production systems................................30 2.2.2 Environmental problems.....................................................................31 2.2.3 Shift back to organic production - towards a sustainable agriculture......................................................................................................34 2.3 Recycling waste into nutrients........................................................................35 2.3.1 Integrating crop and animal production ..........................................35 2.3.2 Managing wastes through composting.............................................36 2.4 Organic vs. conventional farming - economical aspects.............................38 2.5 A closer look at compost..................................................................................40 2.5.1 Definition and process.........................................................................40 2.5.2 Biological, chemical and physical properties...................................41 2.5.3 Effects on soil properties.....................................................................42 2.5.3.1 Chemical aspects...........................................................................43 2.5.3.2 Physical aspects.............................................................................45 5 2.5.4 Effects on soil microorganisms biomass and activity .46 2.5.4.1 The role of soil microorganisms in soil fertility.......................46 2.5.4.2 Factors affecting soil microorganisms.......................................48 2.5.5 Effects on plants....................................................................................50 2.5.6 Effects on weed control .......................................................................51 2.5.7 Practical considerations on the use of compost...............................52 2.5.7.1 Time of application.......................................................................52 2.5.7.2 Method of application..................................................................53 2.5.7.3 Rates of application......................................................................53 Chapter3. General Material and Methods....................................55 3.1 Maize cultivars..................................................................................................55 3.2 Treatments applied...........................................................................................55 3.2.1 Fresh Dairy Manure.............................................................................55 3.2.2 Dairy Manure Compost.......................................................................55 3.2.3 Nitram....................................................................................................56 3.3 Field experiments .............................................................................................56 3.3.1 Site, climate and soils...........................................................................56 3.3.2 Experimental area.................................................................................56 3.3.3 Seedbed preparation and drffling......................................................57