1. Institute of Grassland and Forage Production, Technical Univ. of MunichD‐85350FreisingGermany
2. Institute of Soil Science and Forest Nutrition, Univ. of GöttingenBüsgenweg 2D‐37077GöttingenGermany
3. Natl. Inst. of Public Health and Environ. Protection, Lab. for Waste Materials and EmissionsP.O. Box 1NL‐3720BABilthoventhe Netherlands