Variation in nutrition along time and relative chlorophyll content of Leucospermum cordifolium cv. 'High Gold', and their relationship with chlorotic sypmptoms

Foliar samples, SPAD-502 measurements (both along the growing season), and soil samples were taken from protea plants (Leucospermum cordifolium), cultivar 'High Gold' cultivated in six commercial plantations of La Palma Island (Canarian Archipelago). Soil data (pH, available P, Ca, Mg, K and Na, and EC) ranged within normal levels for proteas, though O.M. was high. Drainage decreased the potential problem that could be caused by the high clay content of the soils. Leaves showed high concentrations of N, K, Mg, and Na, while Ca and Cu were normal. On the other hand, Fe and Zn presented some low foliar levels, while Mn values fluctuated depending upon the different plantations. N contents were higher in spring, and those of K, Ca, Mg, and Na increased with time. Relative chlorophyll contents (SPAD-502 measurements) were compared with macro(N, P, Na, K, Ca, Mg) and micro- (Cu, Fe, Mn, Zn) foliar levels. Results showed no positive correlation between leaf chlorophyll and N content. Higher leaf N concentrations were observed in chlorophyll deficient than chlorophyll sufficient leaves at one site and vice versa at another site. In contrast, lower Mn, Fe and Ca concentrations, the last corresponding with higher ratios of N/Ca were observed in chlorophyll deficient than chlorophyll sufficient leaves at several sites. It is concluded that amendment of soils with Mn, Fe and Ca may prevent the development of chlorophyll deficiency symptoms, associated with diminished photosynthetic capacity, in this important commercial cultivar. (c) 2005 Elsevier B.V. All rights reserved.