The world-wide shortage of plant production menacing the survival of many people demands for more and better research, particularly on how to increase food and where it is most needed. Major problems of international concern for the scientific community are the availability in soil media of macro and micro nutrients and the efficiency of nutrient uptake by plant roots, the interactions between nutrients and other factors, the distribution of nutrients in different plant species, biochemical functions of nutrient elements, and their contribution to plant growth, yield and product quality. Feasibility and profit are also permanent concerns about plant nutrition in crop management, to which new require ments are now imposed by the need to decrease pollution hazards, a problem of prime importance to preserve the environment of the future. is A deeper insight into basic knowledge further required as well as into practical problems in the domains of agriculture, horticulture, and forestry. Such has been the concern of the International Association for the Optimization of Plant Nutrition (IAOPN) since 1964, promoting International Colloquia every four years as an opportunity for scientists concerned with plant nutrition to report new findings and to exchange ideas, experiences, and techniques. The Eighth International Colloquium for the Optimization of Plant Nutrition was hosted by Portugal and held in Lisbon from 31 August to 8 September 1992, with 280 delegates from 34 countries.

Inhalt
A: Plant Analysis Methods and Reference Values for Plant Material.- B: Nutritional Characteristics and Management of Growth Media.- C: Improving the Diagnosis of the Nutritional Status of Crops.- D: Nutrient Uptake and Interactions with Physiological and Biochemical Processes.- E: Mineral Composition in Relation to Crop Growth, Yield and Product Quality.- F: Response to form, Rate and Manner of Application of Fertilizers.- G: Influence of Fertilizers on Yield and Quality of Various Crops.- H: Effects of Heavy Metal Stress on Crop Behaviour.- I: Macronutrients and Environmental Stress.- J: Maximization of Nutrient Utilization in Relation to Environmental Protection.- Author Index.