Can sustainable management models for olive groves adequately satisfy their nutritional needs?

Two sustainable management models were studied, in order to investigate if they were successful in satisfying the nutritional needs of mature olive groves (20 year-old olive trees- Olea europaea, cv. 'Koroneiki'), situated in two geographical regions of Greece (Thessaloniki, Central Macedonia, Northern Greece, and Corfu, Ionian Islands, Western Greece). Nutrient supply in both olive orchards was based, during the last 20 years, on pruning material recycling, as well as on cow manure (8 t/ha/year, in the grove of Corfu) and patent kali (5 kg/tree/year, in the grove of Thessaloniki) application. Soil analysis revealed that pH was slightly alkaline in the olive grove of Thessaloniki and acidic (6.00-6.34) in the olive orchard of Corfu; organic matter content was approximately two times greater in the grove of Corfu. Exchangeable Ca concentrations in deeper soil layers (20-40 and 40-60 cm) of the olive orchard of Thessaloniki were approximately two times greater, compared to those found in the grove of Corfu. In contrast, 2-14.5 times greater K exchangeable concentrations, but only in deeper layers (20-40 and 40-60 cm), were found in the grove of Corfu. DTPA extractable Fe, Mn and Zn concentrations were 9-14, 3-5, and 3-5.5 times greater (depending on soil layer) in the olive orchard of Corfu, compared to those found in Thessaloniki. Leaf K concentrations were significantly greater in the grove of Corfu (1.2-1.4% d.w.), while Fe concentrations in the same olive orchard exceeded 120 ppm. Generally, most of the leaf nutrient concentrations for both groves were within the normal levels of sufficiency, or within the over-sufficiency range (e.g. those of N and K in the grove of Corfu, and P in both olive orchards). Only leaf B concentrations in January (17-19 p.p.m.), in both orchards, and leaf Mn levels in the grove of Corfu were slightly (but not seriously) deficient to marginal. Consequently, it can be concluded that both studied sustainable management models for mature olive groves (no soil tillage, pruning material and weed cuts recycling, in addition to: (i) patent kali, or (ii) manure supply) were successful. Thus, the two models are commercially and environmentally sustainable for olive cultivation, especially in marginal, degraded, and/or hilly Mediterranean areas. Finally, they are of great socioeconomic importance in specific rural areas (where olive-growers combine olive oil production with domestic animal breeding).