Ebook: Handbook for Composting and Compost Use in Organic Horticulture

BioGreenhouse COST Action FA 1105, www.biogreenhouse.org, 2016. —108. —ISBN: 978-94-6257-749-7-108The Growers Handbook on Compost is divided into nine chapters:Chapter 1 presents the ecosystem approach in organic farming, explaining the concept of resilience and biodiversity, and how different farm management styles may incline more towards risk management or towards building long-term resilience. Soil ecosystem resilience is at the basis of organic farming systems, and the chapter highlights how compost can contribute to building resilience into the ecosystem services that the soil provides. When soil imbalance occurs, it is important for the grower to have a good understanding of the different aspects of his or her own soil, before deciding what management options are available. The chapter also explains how a visual soil assessment in the form of a spade test can be carried out, to identify the area in which soil problems exist. From there, soil management decisions can be made, regarding the right type and quality of soil amendments, the application rate, and/or the depth and frequency of tillage.Chapter 2 starts with a brief overview of the characteristics of different feedstocks which can be used in the composting process, and addresses specifically the nutrient contents of different types of manure. Depending on the carbon and nitrogen contents, manure can either be directly composted or mixed with structure- and carbon rich-materials. It also discusses the effects of the application of fresh manure compared to composted manure on amended soil. The next part of the chapter discusses the technical aspects of the composting process and the requirements for the preparation of starting mixes. Different compost types are described. The last part of the chapter gives an overview of the different composting systems that are applied in Europe: from farmer-field edge methods to commercial hall composting.Chapter 3 discusses the microbiology of the composting process. The most important groups of microorganisms involved in the composting process are discussed. The feedstocks that are used in compost production determine the availability of energy in the form of various organic compounds and the presence of nutrients, notably nitrogen. The roles of different microorganisms in the transformation of organic compounds and nitrogen in the various stages of the composting process are discussed. The different phases of the hot composting process are discussed in detail, including the role of specific bacteria and fungi. Finally stability and maturity are defined and the difference between them is explained.In Chapter 4, the management of the composting process is described in terms of parameters that are necessary to control production, including temperature, moisture content, oxygen content and available nitrogen. The maturity level at the end of the composting process can be determined by several tests. The last part of this chapter discusses the most important quality aspects of the final compost product. These include nutrient contents, pH value, salt contents, heavy metal contents, the intensity of colour extracts, and the presence of pathogens and weeds.Chapter 5 describes the hygienization aspects of composting. This includes not only plant pathogens and weeds, but also animal and human pathogens. The mechanisms through which pathogens are eradicated during the composting process are described, and the relevant aspects of risk pathogens are discussed. The next part of the chapter describes the main entries for plant pathogens and human pathogens in compost feedstocks. The last part of the chapter describes the critical aspects of the composting process, where improper handling may lead to failure of inactivation of pathogens.In Chapter 6 the phenomenon of natural disease suppression is described: What is it exactly and how can it be recognized in practice. Furthermore, the chapter deals with the use of compost to increase disease suppression and how compost may aid to combat soil-borne diseases such as plant pathogenic fungi, bacteria and nematodes.Chapter 7 describes the main differences between compost (produce aerobically) and digestate (resulting from anaerobic digestion). Both have specific characteristics which influence their utilization. Digestate has a stronger but shorter term fertilization effect than compost, but compost has better medium- and long-term effects on humus content and soil structure than digestate. So, depending on the target use, compost and digestate have specific advantages and disadvantages, opportunities and limits.Chapter 8 describes how compost influences diverse properties of soil and growing media such as water content and nutrient supply. In addition, it is indicated how the quality of the compost can be measured.Chapter 9 describes how growers can assess compost quality in order to choose the appropriate compost for the target application. There is a range of different methods that can help the grower to choose: observation with own senses, simple chemical analyses and bio-tests. In this chapter, these methods are briefly described and the interpretation of the obtained results is discussed.