PHYSIOLOGICAL AND BIOCHEMICAL ASPECTS OF MINERAL NUTRITION OF DECIDUOUS FRUIT TREES: SIGNIFICANCE FOR IMPROVED YIELD AND FRUIT QUALITY; INTERPRETATION OF PLANT ANALYSIS DATA AND NUTRIENT ACQUISITION

It is obvious that in production of deciduous fruits the physiological and biochemical role of the various mineral nutrients often are not well considered. As a consequence, in the practice there are uncertainties with the various recommendations or they are not well defined. Thus, there is still a great necessity for applied research on optimal mineral nutrition of fruit trees (and as a consequence also on adequate fertilizer application) to make fruit production economically competitive. Examples will be given for misinterpretation of deficiency symptoms and how inadequate mineral nutrition may result in yield losses and low fruit quality. In detail effects of improved nutritional status on flower initiation and development, translocation of assimilates and fruit quality (bitter pit) will be discussed.

Optimized mineral nutrition for high yield and good quality, however, does not need in each case high fertilizer applications. Selfregulation of nutrient uptake and adaptive mechanisms for nutrient acquisition in fruit trees including rhizosphere processes have to be considered for fertilization recommendation to minimize mineral fertilizer use.