Nutritional Status in Loquat Trees by Using the SPAD

Abstract

The aim of this work was to verify the possibility to determine mineral nutritional status in loquat leaves by using the portable instrument Chlorophyll Meter SPAD-502 (Minolta). For some species SPAD values have already been correlated to leaf chlorophyll concentration and leaf nitrogen level. SPAD has all requirements for the easy, handy and non destructive measurements. The work was carried out in Valencia (Spain) on 25-year-old loquat trees (Eriobotrya japonica Lindl. `Algerie¿), grafted onto seedlings, with visible differences on leaf colour, from deep green to yellowish leaf colour. Early in summer, leaves from current shoots, grouped in 10 groups according to colour, were SPAD measured and then collected for analysis, groups containing 20 leaves each. Total N of leaves was determined by the micro-Kjeldhal method, and cations K, Mn, Ca, Mg, Fe and Zn with an atomic emission spectrometer with an inductively coupled plasma as excitation source (Spectro ICICP-D, Germany).The results showed significant correlation between SPAD units and leaf N content, but not with cations content. The SPAD can be used to determine nitrogen status of loquat trees, in order to check fertilization.