Use of Chlorophyll Meter to Assess the Effect of Nitrogen on Sweet Pepper Development and Growth

Abstract

The evolution of both leaf expansion and chlorophyll content was assessed in potted sweet pepper plants subjected to four different levels of nitrogen (mg N/kg of soil): N1 = 25 (basal dressing); N2 = 50 (basal dressing); N3 = 100 (basal dressing and one side dressing); and, N4 = 150 (basal dressing and two side dressings). In each plant, the first leaves (numbered 1–5) were chosen at the main stem and the next four ramifications. The relative chlorophyll content of leaves 1 to 5, from all treatments, was obtained by a portable chlorophyll meter, SPAD-502, twice a week. The SPAD readings were subsequently converted into total chlorophyll (μ g cm− 2). The plant dry weight, the number of fruits per plant, and the N content of leaves were measured at final harvest (70 d after transplantation, DAT). Until the first side dressing (35 DAT), the increase in chlorophyll content was similar in all treatments, decreasing afterward under the N1 and N2 treatments (leaves 1 and 2), while under the N3 and N4 treatments the increase in the chlorophyll content continued after the first side dressing. The application of the second side dressing (53 DAT) under the N4 treatment induced a subsequent increase in chlorophyll content in all leaves compared with those of N3. An early senescence was observed under the N1 and N2 treatments compared with the others. Applied N in side dressing led to an increase in leaf width (leaves 2–5) and longevity, mainly in leaves 2 and 3, and a subsequent increase under fruit number and fruit dry weight under the N3 and N4 treatments.