Abstract

RUBIO-COVARRUBIAS, Oswaldo A.; BROWN, Patrick H.  and  WEIBAUM, Steven A.. Seasonal, diurnal, and within canopy variation of leaf nitrogen compounds in almond and nectarine leaves. Terra Latinoam [online]. 2009, vol.27, n.3, pp.187-196. ISSN 2395-8030.

Traditionally, total leaf nitrogen has been used to indicate the nutritional status of orchard trees. With the objective of exploring new alternatives, in the present study we tested different nitrogen compounds as indicators and determined their variability in the tree canopy over time. The seasonal, diurnal and positional variability of nitrate, ammonium, soluble nitrogen (SN) extracted with formic acid 0.2 N, as well as total nitrogen (TN) were determined in the leaves of young field-grown almond (Prunus dulcis (Mill) D. A. Webb) and nectarine (Prunuspersica L. Batsch) trees. Over a 3 year period, four nitrogen treatments (0, 78, 157, and 313 g N tree^-1 year^-1) were established in field grown trees. The third year two treatments (0 and 157 g N tree^-1 year^-1), representing nitrogen deficiency and sufficiency, respectively, were chosen for leaf analysis. Both species showed high concentrations of ammonium, SN and TN at the beginning of season. However, in Nfertilized almond and nectarine trees, ammonium and SN tended to increase slightly during the day after 9:00 h. In contrast, nitrate exhibited the opposite trend. Leaf TN and SN concentrations decreased from the apical to the basal leaves while nitrate concentrations showed and opposite tendency and ammonium did not vary consistently. All the nitrogen compounds in the leaves of both species were sensitive to the nitrogen supplied. However, considering the variability of the nitrogen compounds over time, within tree canopies and, in particular, the variability among trees with the same fertilization treatment, it was concluded that TN was the best nitrogen indicator.

Keywords : Prunus dulcis; Prunus persica; ammonium; nitrate; soluble nitrogen.

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