Dynamics of minerals and nutrient imbalances in olive leaves under tillage and annual legume cover crops
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abstract
The concentration of minerals in leaves depends on phenology, crop yield, soil
characteristics, environmental conditions and agronomic practices. This study was
undertaken to compare the dynamics of minerals of olive rainfed trees under tillage
(two per year) with trees in consociation with a mixture of 11 early season self-reseeding
Legumes. The results of leaf minerals concentrations, on both treatments, showed
similar variation between sampling dates, with higher levels of N, P, K, B and Zn found in
summer, at endocarp sclerification, and of Ca, Mg, Fe and Mn at winter resting period,
resulting in statistically significant changes on nutrient ratios, with higher Ca, Mg, Fe and
Mn-to-N and Ca:Mg and Fe:Mn ratios and Lower K, P, B, Cu and Zn-to-N and K:Ca, K:Mg,
Cu:Zn, Zn:Fe and Zn:Mn ratios during winter. Trees of plots managed with the cover
crop had higher concentrations of N, Mg and Mn, in close association with leaf water
status, photosynthetic activity and crop yield. Moreover, legumes plots presented
significant higher Mg and Mn-to-N ratios and Lower P, Fe and 8-to-N ratios, as well
lower K:Mg, Ca:Mg, Fe:Mn and Zn:Mn ratios on both dates, and lower K and Cu-to-N
ratios during summer. Although only Cu values were higher than typical sufficient Levels,
important relative nutrient changes were found. Phosphorus and Mg-to-N ratios were
above the optimal ratios for olive leaves, on both seasons, the Fe: N ratio was over
during winter, the Mn:N ratio was higher under cover crop, the K:N ratio was Lower at
winter and Ca:N was below the reference Levels during summer. These results
highlighted that nutrient ratios can be more indicative than nutrient concentrations
regarded as optimal for olive. lt is important to standardise the procedures for leaf
sampling and to define target values for nutrient ratios in different conditions, in order
to detect and, if necessary, to correct nutrient imbalances.
This work was funded by the INTERACT project- "Integrative Research in Environment, Agro-Chains and
Technology'', no. NORTE-01-0145-FEDER-000017, in its lines of research entitled ISAC, eo-financed by the
European Regional Development Fund (ERDF) through NORTE 2020 (North Regional Operational Program
2014/2020).