A MULTIVARIATE DIAGNOSIS APPROACH APPLIED TO CELERY

Celery (Apium graveolens L. var Dulce) is a high value crop affected a t different growth stages by a variety of nutrient disorders. Each nut rient concentration can be corrected for its dependence on concentrati ons of other nutrients by recognizing plant composition as a closed sy stem whose components add up to one. New variables z(i) are computed a s logratioed values of individual nutrients, where each nutrient conce ntration is corrected for the geometric mean of all nutrient concentra tions. The z(i) are used together with principal component analysis (P CA) to relate celery composition to yield, deficiency symptoms and qua lity parameters. A survey of commercial celery fields suggested that ( 1) celery growth is most often limited by P and N deficiencies associa ted with Fe toxicity; (2) K uptake is most likely to become limiting w hen the crop reaches 15 cm in height; (3) blackheart incidence can be traced to low levels of K and Mg in external petioles, and (4) cracked stem incidence is related to low B when the crop is 30 cm in height.