Effects of foliar-applied nitrogen during winter on growth, nitrogen content and production of passionfruit

Abstract

The effects of foliar-applied nitrogen (11.5 g N l−1) during winter on growth, nitrogen content and production of passionfruit (Passiflora edulis f. edulis × P. edulis f. flavicarpa cultivar E-23 grafted onto P. edulis f. flavicarpa) was investigated in subtropical Queensland, Australia. Vegetative growth and flowering were severely restricted during winter in the untreated vines, despite the maintenance of leaf nitrogen levels within the range presently believed to be optimum for Queensland conditions after nitrogen was applied to the soil in autumn. Foliar urea applications during winter (monthly or twice monthly) increased leaf nitrogen levels but reduced growth and subsequent fruitlet number.

Reductions in vegetative growth during winter in passionfruit appear to be due to a direct effect of cool soil and/or air temperatures, unrelated to nitrogen uptake, translocation and leaf nitrogen level.