This paper briefly discusses global human requirements of protein nitrogen (N) from crops and animals, and then estimates the need for fertilizer N as a function of N use efficiency, and the recycling of N from animal manure and sewage wastes. | Turk J Agric For 32 (2008) 165-176 © TÜB‹TAK Global Economics of Nutrient Cycling Bert H. JANSSEN1,*, Oene OENEMA2 1 Plant Production Systems Group, Wageningen University, Wageningen, THE NETHERLANDS 2 Environmental Sciences Group, Alterra, Wageningen UR, Wageningen, THE NETHERLANDS Received: Abstract: This paper briefly discusses global human requirements of protein nitrogen (N) from crops and animals, and then estimates the need for fertilizer N as a function of N use efficiency, and the recycling of N from animal manure and sewage wastes. These estimates are based on various assumptions and simple calculations. Results suggest that globally only 1% of N input is retained, 28% is lost to the wider environment, and some 70% is potentially available for recycling via manure and sewage. In addition, large amounts of nutrients recycle via crop residues. In practice, only a fraction of this potential is realized, in part because of the segregation of crop production systems from animal production (land-less livestock) systems and of the lack of economic incentives for recycling. As a consequence, nutrient use efficiency is low and nutrients are lost to the environment and create a cascade of unwanted side-effects. To economize on nutrients, side-effects of their use have to be internalized in decision making. This may be done via deposits and/or taxes to emphasize the non-disposal nature of nutrients. Increasingly, government policies provide incentives for recycling nutrients, but there are clear limits to the implementation of environmental regulations. Instead, we foresee a role for the fertilizer industry in processing and recycling animal manure from land-less livestock systems. Key Words: crop production, economics, land requirement, livestock, manure, nutrient cycling Introduction The title of this paper sounds ambitious and may promise more than can be offered within the limits of one article; therefore, we will first explain what is .
