Christina Giourga

Olive groves: ``The life and identity of the Mediterranean''

Olive tree cultivation in theMediterranean goes back to ancient times. Evensince the Roman Age, olive cultivation spreadto the entire Mediterranean basin. Thislongevous tree integrates and identifieseconomically, socially, and culturally theinhabitants of this basin and determines itsrural landscape. For the residents of theMediterranean, olive oil constituted the mainsource of nutritional fats, their most valuableexport product, and was identified with theirculture. Even now, olive cultivation has amultiple importance for the Mediterranean. Theolive groves, which grow mostly on inclined,shallow, and low fertility soils, and onhand-made stone terraces, have limited wateringrequirements and sustain the fragile naturalresources of the Mediterranean. Today,olive cultivation in the Mediterranean is anadditional income source and supports thepopulation in rural areas during the winterperiod, which profit from summer and seatourism activity. Although anagro-ecosystem, the olive grove resembles thenatural Mediterranean ecosystem and abandonmenttransforms them into natural Mediterranean typeforests. Their change of use from olivecultivation to pasture degrades the ecosystemand decreases the natural resources, because ofover-grazing. At this time, two major factorsthreaten the traditional olive cultivation (i)the competition of the intensive olive grovesin plain and irrigated areas and (ii) thecheaper seed-oils, which intensify theabandonment of traditional olive groves andchange them into pasture, resulting in thedeterioration of the ecosystem. Olivecultivation has left its mark on life in theMediterranean and has contributed to thesustainability of natural resources.Nevertheless, it succumbs under the pressure ofcurrent socioeconomic situations. Today, theconservation of olives in productionconstitutes a necessity for the fragileMediterranean ecosystems and a challenge foreverybody involved.

Ecological Patterns and Comparative Nutrient Dynamics of Natural and Agricultural Mediterranean-Type Ecosystems

An agricultural watershed, situated on an island of the Aegean archipelago, was studied in order to gain insight into the structure and the design of a typical terrestrial ecosystem of the Mediterranean region. Fieldwork was focused on the comparative study of seasonal patterns of inorganic nutrients, organic nitrogen, and erosion over the most abundant vegetation types of the area, such as olive groves, maquis, and wetlands. Nutrient losses via the pathway of erosion were provided by the determination of nutrient concentrations in runoff sediments. Results showed that nutrient levels are higher and more susceptible to rapid changes in the zones that host agricultural activities and animal husbandry. The behavior of nitrogen and phosphorus showed remarkable stability in the maquis, where dynamic processes were mainly affected by soil erosion, which led gradually to land degradation, especially on sloping terrains. The aim of this study was to form the basis for the quantification of the interconnections within the Mediterranean-type ecosystems and to conceptualize their operational properties.

Assessing Nitrogen Fertilization Strategies in Winter Wheat and Cotton Crops in Northern Greece

The management of fertilizer application is crucial for agricultural production and environmental safety. The objective of this study was to assess the efficiency of different fertilization strategies, applying fertilizers with and without nitrification inhibitors (NIs) in split application, in Greece. The assessment criteria used were based on crop yield, soil nitrogen (N) concentrations and economic efficiency. For this purpose two crops (winter wheat and cotton) were selected in order to explore the optimum fertilization strategy for each crop. Three treatments combining fertilizers with NIs were tested compared with conventional fertilization (CF). Slight differences in the quantity and the combination of fertilizers with NIs applied resulted in variable effects on crop yield, soil N and economic return. Split N application of 102 kg ha −1 , with half of the total amount applied at seeding, resulted in higher grain yield of winter wheat, lower NO3-N in soil and higher economic return. This result reveals the importance of N application at seeding in wheat crop. Fertilization strategy with 109.5 kg N ha −1 and split P application resulted in higher cotton yield and higher economic profit. Split P application seemed to increase yield, even though it is not a common practise in the area.

Land-Use Effect on Selected Soil Quality Parameters

Land use is a key factor that affects soil quality. The purpose of the present study was to investigate changes of selected soil chemical properties related to soil function under different land uses. Five experimental sites arranged in a complete randomized blocks located within the Kalloni watershed (Lesvos Island, Greece) corresponding to different land uses (Pinus brutia forest, brushwood pasture, rain-fed olive grove, wheat, and maize) were compared for soil pH, electrical conductivity (EC), total nitrogen (N), nitrate N (NO3-N), Olsen phosphorus (P), and organic matter. Soil nitrate and P concentration were in the order corn > wheat > olive > pasture > forest. Soil EC and NO3-N showed significant within-year variability only in the corn and wheat systems. Corn and wheat had the lowest soil organic-matter content followed the order forest > pasture > olive grove = wheat = corn. However, total N did not significantly differ among land uses.

Effect of Land-Use History on Soil Carbon and Nitrogen in a Mediterranean Catchment

The impact of land use on soil organic matter was investigated. Five land cover types (pine forest, olive groves, wheat, wheat/maize cultivation systems, and a shrub pasture) belonging to three land-use categories from the same catchment in the island of Lesvos, Greece, were used. The soils developed under similar pedogenetic processes and accepted similar agricultural practices for at least 30 years. The results showed that the land-use and cover types ranged according to their total soil carbon (C) content as follows: forest > double cultivation > wheat > olive > pasture. Crop plantations contained 31 to 40% less C at their upper 0- to 45-cm layer than forest. Pasture had shallow soils with a small C accumulation but high C concentration, whereas olive groves had the lowest concentrations of both soil C and nitrogen (N). Olive grove soils were the most prone to degradation but possessed the greatest potential for C sequestration.