1. Univ. of Technology; Dep. of Agriculture; Private Mail Bag Lae Papua New Guinea
2. Dep. of Soil Science and Plant Nutrition; Wageningen Agricultural Univ.; P.O. Box 8005 6700 EC Wageningen the Netherlands
3. International Centre for Research in Agroforestry (ICRAF); P.O. Box 30677 Nairobi Kenya