| Summary: | The project reported here took place in Messara plain, Crete, Greece, a semi-arid Mediterranean region. It involved a literature review (Chapter 1), a field survey (Chapter 2), two field experiments (Chapters 3 and Chapter 4) and associated laboratory analyses. The survey took place in three crop years using pairs of neighbouring organic and conventional commercial olive orchards of the cultivar Koroneiki at the valley and the surrounding hills. Both field experiments took place in a 2.4 ha table olive orchard consisted of trees of Kalamon and Manzanila olive cultivars for three crop years. Results from the field survey (Chapter 2) indicate that organic olive oil production systems developed in the Messara plain can produce the same or higher yields of oil than conventional production in the same area. Although olive oil produced from both systems is of similar quality, slightly but significantly higher levels of acidity were detected in organic olive oil. Pesticide contamination was identified as a problem in both organic and conventional production with endosulphan sulphate being the main pesticide residue. This will have to be resolved to preserve the reputation of the region for high quality oil production. Improvement in cover cropping was the main target in the 1st field experiment (Chapter 3). There were few significant effects of cover crops/cover crop mixtures on nutrient availability, invertebrate activity, and yield parameters. Rhizobium inoculation had a negative effect on Vicia sativa establishment but did not affect any of the nodulation parameters assessed. The highest levels of Hymenoptera activity were found in the cover crop mixture consisting of vetch, peas and barley. Also, the non-inoculated vetch and the cover crop mixture reduced the concentrations of olive leaf boron. The development of improved olive fruit fly management strategies was the main target in the 2nd field experiment (Chapter 4). Wind direction, humidity, rainfall and temperature were identified as important potential environmental drivers for olive fly pest pressure in the Messara region. Also, results indicate that soil survival is probably not an important over-wintering mechanism for the olive fly in the Messara plain and other semiarid Mediterranean regions. The two mass trapping systems compared differ significantly with respect to number of non-target invertebrates killed, but caught similar numbers of olive fruit flies. Results also indicated that the dates for placing mass-traps into orchard may need to be revised and related to the drivers of olive fly pressure.
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