1 Crop-livestock systems: old wine in new bottles?

www.laventana.nl Many farmers in tropical and temperate countries manage a mix of crops and animals. In these systems crop residues can be used to feed the animals and the excreta from the animals as nutrients for the crops. Other forms of mixing take place where grazing under fruit-trees keeps the grass short, where manure from pigs is used to 'feed ' fish in a pond or where young animals bred in remote areas are fattened near urban centres with high demands for meat. In addition, inclusion of livestock alters the rate of nutrient turnover, it provides a labour opportunity in slack times for crops and adds value to crop (by-)products. Livestock thus affects the socio-economic and biophysical dynamics of the entire farming system. Indeed, a wide variety of forms and processes in mixed farming are known world-wide. To different degrees they are all essential for the livelihood of farmers and for the production of food and other commodities for cities and export markets. More recently, even highly specialised crop and livestock systems in developed and developing countries have rediscovered the advantages of mixed farming. Specialised industrial pig and poultry farmers have been banned from densely populated countries such as Singapore, and in Western Europe they are obliged by law to exchange their dung surpluses with crop farmers. Moreover