Many farmers in tropical and temperate countries survive by managing a mix of different crops and/or animals. The best known form of mixed farming is when crop residues are used to feed the animals and the excreta from the animals are used as nutrients for the crops. Other forms of mixing take place where grazing under fruit-trees keeps the grass short, or where manure from pigs is used to "feed" the fish pond. Traditionally, a wide variety of mixed farming systems has been used worldwide. These systems are essential for the livelihood of farmers and for the production of food and other commodities for the cities and export markets. Even many highly specialized crop and livestock systems in developed and developing countries are rediscovering the advantages of mixed farming. For example, specialized industrial pig and poultry farmers are banned from modern countries such as Singapore, and in western Europe they are forced to exchange their dung surpluses with crop farmers. Moreover, the essence of many modern organic farming systems lies in the mixing of crops and animals.
What is the essence of mixed farming, how important is it, is it something of the past or is it a new vision for the future? Where and how does mixed farming occur and what can be done to make it more productive while at the same time giving due attention to aspects of sustainability? These are the main issues discussed in Chapters 2 and 3, which explain several forms of mixing and ways to characterize them on the basis of the relative availability of production factors - land, labour and capital. The similarity between issues of mixing in agriculture and in society is also apparent. In the same way that dung from animals is recycled for use on crops, it becomes increasingly important in cities to recycle newspapers, glass, tin cans, etc. Recycling can be necessary because of a lack of resources, such as in low external input agriculture (LEIA), and as a result of problems with waste disposal in high external input agriculture (HEIA).
Conservation farming in Kenya: anti-erosion bunds are planted with grass that can be used to feed animals
A specialized dairy farm with buffaloes in India: these dung surpluses will be hard to recycle if the neighbourhood turns from rice fields into suburbs
Chapters 4 to 7 present a series of traditional technologies and their suitability under different conditions, together with examples of social organization to make various technologies successful. The existence of many different mixed farming systems and modes of production has at least two implications. The first refers to a wide variation in the types of technologies and management practices. The second refers to the fact that no one technology or a few technologies can be suitable for a wide range of systems. However, much can still be done in terms of traditional techniques for mixed farming, and these chapters focus on areas such as:
The wide range of technologies for mixed farming has made it necessary to be selective, i.e. only some animal species are discussed in Chapter 4; only some aspects of disease, feeding and breeding are discussed in Chapter 5; nutrient cycling is discussed in Chapter 6 in a condensed way; while some aspects of social organization and management are given in Chapter 7. Chapter 8 presents a series of mixed farming systems that have proved to be successful over a longer period of time, together with some general conclusions.
The thinking behind this publication is based on modern insight from system theory and it is stressed that there is no such thing as one solution for all problems. Technologies and management methods can be very useful, but mostly only under certain conditions and circumstances. On the other hand, innovations to cope with changing farming systems are found everywhere. Not only can research provide new technologies, but the farmers themselves can also search for ways to cope with change. They modify traditional technologies and adopt and adapt methods passed on from colleagues and formal research centres.
Throughout it is aimed to show that the thinking and technicalities behind the mixing of several enterprises are things for the future, not only for the past, and not only for agriculture but also for society in general. Perhaps the biggest change that could or should take place to "improve" mixed systems is that farmers and development workers start to see the development of a part of the system in the context of the whole. This can be called the "communal ideotype", which implies that farmers and researchers should aim for maximum but sustainable output of the farm, sometimes at the expense of the output of an individual crop or animal. Another change is perhaps that official research recognizes farmers' experience and participation as assets to modify new technologies for their own variable conditions. Today this is already accounted for in many research and development projects that are implemented in developing countries but much more can be done.