Micronutrient Symposium INTRODUCTION The subject of minor element, trace element, or micronutrient deficiencies in soils, plants, a n d animals i s well documented in the technical literature. These nutrient elements frequently a r e of major importance in efficient crop production. They are required in measurable proportions rather than in true trace quantities. Hence, the accepted term has become micronutrient, implying that the required amounts o f these nutrients a r e generally small in comparison with crop demand f o r macronutrients. Research has been a n invaluable a i d in dealing with micronutrient problems in many regions o f the world. Certain of these nutrients have been applied regularly to specific areas of soil and to particular crops for a long direct time. The use of micronutrients i s increasing-as additions t o the soil, as foliage sprays, and as constituents
o f mixed fertilizers. New d a t a on their chemistry, manufacture, and use a r e continually being revealed b y able scientists in research and deve!opment. The p a r ticipants in this symposium a r e outstanding leaders in the micronuirients field. In developing the symposium, the purpose was t o correlate the subject matter in the form of a survey of the present-day needs for micronutrients, the properties o f materials supplying these needs, and the routes b y which the needs are satisfied. The following contributions t o the symposium meet this g o a l in an admirable manner.
JOHN 0. HARDESTY, Symposium Chairman U. S. Department o f Agriculture, Beltsville, Md. -
MICRONUTRIENT R E S E A R C H
Introduction to Micronutrient Elements
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THE P A S r T J L~ ~ Y T YE 4r
