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Olive trees constitute one of the most dynamic cultivations for Mediterranean countries, while their economic importance is high. As water constitutes a fundamental factor affecting olive tree production, soil water content is a most critical parameter that must be monitored to improve olive trees’ cultivation management. Effects of precipitation, irrigation, and soil management on water content in four soil depths (10, 20, 30, 40 cm), four periods of the year (February–March, April–May, June–July, August–September) and three successive years were determined in 12 Mediterranean olive groves (Trifilia, southern Greece) as well as their respective fruit and olive oil yields. Significantly higher soil water content was recorded in the first (+16.8%) and third (+27.4%) year compared to the second year. Higher (+6.8%) water content was observed in irrigated olive groves compared to rainfed fields. Higher (+5.6%) water content was observed in sustainable olive groves compared to intensively managed fields. Significantly, higher soil moisture was recorded at 40 and 30 cm depth compared to 10 cm depth while intermediate values were observed at 20 cm. Marked increase in fruit yield was achieved through sustainable management (+39%) compared to intensive olive groves. The potential to improve irrigation practices in the area was also indicated by results of the present study.

The objective of this work was to classify and map the areas environmentally sensitive to desertification in the Mediterranean island of Crete. Sensitivity to desertification was estimated with a modification of the MEDALUS Environmentally Sensitive Area Index (ESAI) approach, using 15 quantitative parameters divided into four main quality indices: climate, vegetation, soils and management quality. The ESAI methodology was modified to include two additional parameters related to soil quality (water erosion and soil organic matter). According to the results, 37% of the island's area is characterized as critically sensitive to desertification. This percentage varies significantly across the island, with the western part having the least critically sensitive areas, and the eastern part the most critically sensitive. The results of this study also indicate that critically sensitive areas are found in the eastern side of the island mainly due to human-related factors and climatic conditions. It was concluded that the proposed methodology is a valuable tool for regional-scale assessment of areas environmentally sensitive to desertification in Mediterranean environments.

Olive trees are a major source of agricultural residues. Strategies based on different management of organic amendments have been reported to increase soil fertility. The effect of sustainable organic matter input practices (application of shredded pruning residue and olive residue compost to soil) on soil properties in irrigated and rain-fed olive groves was investigated. The study took place in 40 olive groves in the region of Peza, island of Crete, Greece during a 5-year period (2012–2017). The results showed that olive trees play an important role in soil nutrient conservation under semi-arid conditions in the Mediterranean basin. The addition of olive tree residues, in combination with conservation tillage practices, improved soil fertility over the experimental period. Most of the soil properties were favored by irrigation. In olive soil parcels receiving organic materials the soil organic matter and the total nitrogen were increased in irrigated fields. The ability of surface soil to sequester carbon and nutrients beneath the tree canopy of olive groves was high. It is recommended that sustainable soil management practices should consider soil fertility variability of olive orchards.

The effect of addition of organic materials (shredded pruning residues, composted olive mill by-products) on spatial distribution of soil chemical and microbial properties in irrigated and rainfed olive groves was investigated. Most of the soil parcels were subjected to reduced tillage or no tillage practices. Soil sampling took place in 40 olive groves in the region of Messinia, south-western Peloponnese, Greece during a 5-year period (2012–2017). The results showed significant increases in soil organic matter, humic acids and nitrate content at the end of the study period, compared to the first year of the soil sampling campaign. On the other hand, the relatively low amount of fresh organic materials that was applied to the soil produced unfavorable results. Differences between irrigated and rainfed soil parcels were not significant, for most of the soil properties, since the area receives much higher loads of rain than the average rainfall, as registered in the main olive growing regions of Greece. The area underneath the tree canopy favors an environment that enhances soil fertility, compared to the area out of the tree canopy. Changes of soil properties according to depth showed that the surface soil in olive orchards has the potential to sequester carbon and nutrients.

The aim of the present study was to determine the short-term effects (three years) of four sustainable management systems including different carbon inputs (compost, pruning residues and cover crops, applied solely or combined) on the mineral content of soil, olive trees and weeds, on some specific groups of soil microorganisms, and on weed mycorrhizal colonization in an olive orchard compared to a conventional system involving soil tillage and only mineral forms of fertilizers. The study was performed between 2013 and 2015 in a 40-year-old olive plantation. The results showed that soil organic matter, as well as main macro- and micronutrients, were markedly improved following three years of increased biomass inputs. Data related to the mycorrhizal colonization of spontaneous weed flora and to actinobacteria, Azotobacter and proteolytic bacteria suggest favourable effects on soil biology and agro-ecosystem complexity. Sowing a mixture of winter cover crops for three successive years also contributed to soil enrichment in biological as well as mineral nutrient aspects. Adoption of the sustainable management here applied practices is in complete agreement with the European policy on the transition from a linear to a circular economy and would provide significant benefits for rural stakeholders and ecosystems in the long term.