Assessment of nitrogenized nutrition of citrus rootstocks using chlorophyll concentrations in the leaf

The objective of this study was to evaluate the nitrogen (N) nutrition in lemon tree rootstocks "Cravo" (Citrus limonia Osbeck) and "Volkameriano" (Citrus volkameriana Ten. e Pasq.) and mandarin tree rootstocks "Cleopatra" (Citrus reshni Hort. ex Tan.) and "Sunki" (Citrus sunki Flort. ex Tan.), using the chlorophyll concentration in the rootstock leaves, grown in 3.0 dm(3) capacity container in a greenhouse. Nitrogen was added to the lemon tree substrate at 0, 158, 316, 474, and 632 mg/dm(3), and 0, 193, 386, 579, and 772 mg/dm(3) were added to the mandarin trees. These N quantities were divided into 20 urea applications for the lemon trees and 24 applications for the mandarin trees during the experiment. The experiment consisted of a factorial arrangement (4 x 5), carried out in a randomized block design, with three replications. The experimental unit consisted of four containers, with one plant per container. The chlorophyll concentration, measured by the Arnon standard method and by the SPAD-502 portable apparatus, were affected by the N. In general, the rootstocks presented little variation in the chlorophyll concentration measured in the leaves. These values were positively correlated with the growth characteristics and N concentration in the leaves, indicating that N can be monitored using such determinations.