DECREASED NITROGEN RATES AND IRRIGATION EFFECT ON CELERY YIELD AND INTERNAL QUALITY

The effect of decreased nitrogen rates (90, 60 and 30 kg N/ha) with an d without irrigation on celery yield quantity and internal quality wer e studied in field experiments in 1993 and 1994. The decreased nitroge n rates reduced yields in both years. In the dry and warm conditions o f 1994 nitrogen x irrigation interaction was clearly observed; irrigat ion increased yield more at higher nitrogen rates than at lower nitrog en rates. In the rainy conditions of 1993 irrigation did not effect th e yield level. On the other hand, in both years, decreased nitrogen ra tes increased dry matter, vitamin C and dietary fiber contents, and ni trogen had a minor effect on total sugar content. In 1994 alpha-and be ta carotene and thiamin were also analyzed but nitrogen had no effect on them. Irrigation increased dry matter and total sugar contents at t he two lowest nitrogen rates in 1994, but decreased vitamin C contents in both years. There was also slight evidence that irrigation might d ecrease a]pha-and beta-carotene and thiamin contents.