Seasonal dynamics of leaf macro- and micronutrients in three commercial avocado varieties at Mojo and Melkassa, Ethiopia

Seasonal leaf nutrient data needed to guide fertilization are scarce for Ethiopian avocado orchards. We measured total nitrogen (TN), Ca, Cu, Fe, Mn and Zn in leaves of tagged Hass, Fuerte and Ettinger trees at the Melkassa Agricultural Research Center (February–July) and of Hass trees on three farms at Mojo (February–June), and described the soils of both sites. Data were analysed with linear mixed models, Tukey’s test and repeated-measures correlation. Mean leaf TN (1.13–1.41%) was below the sufficiency range in all varieties and did not differ significantly between months, varieties or sites, and leaf Zn was below 20 mg/kg in most samples. Leaf Ca increased from 0.79–1.00% in February to 1.61–1.65% in July in all varieties at Melkassa. Cu, Fe, Mn and Zn followed variety-specific seasonal patterns, and Hass leaves at Mojo contained more Mn, Cu and Zn than those at Melkassa. Within trees, Mn was positively correlated with Ca in all varieties and with Cu and Zn in Hass and Fuerte. Soils at both sites were neutral to alkaline (pH 7.24–8.50), very low to low in TN (0.05–0.18%) and mostly very low to low in DTPA-extractable Zn and Fe, in line with the low leaf N and Zn. Nitrogen and zinc supply may limit both orchards, leaf Fe should be monitored on these alkaline soils, and leaf samples for diagnosis should be taken at a fixed time of year because Ca and micronutrients change strongly with season.