1. Day, A. D., McFadyen, J. A., Tucker, T. C., and Cluff, C. B.: 1981, J. Environ. Qual. 10, 47.
2. Epstein, L., Ditz, K., and Saffr, G. R.: 1982, J. Environ. Qual. 11, 65.
3. Feigin, A., Vaisman, L, and Bielorai, H.: 1984, J. Environ. Qual. 13, 234.
4. Jackson, M. L.: 1958, Soil Chemical Analysis, Publ. Prentice Hall International, Inc., London.
5. Juwarkar, Asha and Shende, G. B.: 1985, Effects of Sewage and Sludge Application to Crops. Effects on Rhizobium and Nodulation of Moong and Pea, Proceedings 26th Annual Conferences of AMI, 10?12 October.