Vasileios A. Tzanakakis

Soils are increasingly receiving treated wastewater (TWW) to support crop production and protect natural resources. However, besides water, various inputs, such as soil nutrients (salts), organic carbon, and various contaminants of emerging concern, including antibiotics, antibiotic resistance genes, pharmaceutical compounds, heavy metals, and microplastics, can be delivered. This review aims at (a) an integrated and mechanistic synthesis of current knowledge on potential impacts of TWW irrigation on key soil nitrogen turnover processes, such as nitrogen mineralization, nitrification, denitrification, and ammonia volatilization, and their drivers, and (b) identification of key knowledge and conceptual uncertainties to support future studies. Across the synthesis, no single, uniform TWW effect emerges. In fact, outcomes are consistently conditional on several co‐factors, such as treatment level, irrigation duration, soil type, and plant species, with the latter two sometimes exerting effects exceeding those of water quality itself. TWW alters soil conditions through substrate availability, redox dynamics, soil acidity and salinity, and contaminant exposure, but the mechanistic evidence linking specific drivers to specific nitrogen‐process outcomes is itself uneven. Identified knowledge and methodological gaps suggest long‐term field studies across TWW regimes, soil types, and climates; designs capable of disentangling co‐varying drivers at field scale; and laboratory studies addressing contaminant‐specific impacts, microbial functional persistence, and potential decoupling between nitrogen and carbon dynamics, an effect already evident, though unexplored as a general phenomenon, within the reviewed literature. Overall, this review offers an integrated, system‐level framework to support the evidence‐based management of environmentally and climate‐vulnerable soils receiving reclaimed or even conventional irrigation water.

Scaligeria napiformis (Willd. ex Spreng) Grande is an underutilized wild edible plant associated with the Cretan flora and diet, yet cultivation-oriented information on its response to nutrient management remains limited. This study compared two practical foliar nutrient management regimes, including a biostimulant-containing foliar product (INM-b) and a conventional foliar fertilization regime (CovF), together with an untreated control (Ctrl). Relative chlorophyll status, assessed by SPAD, maximum quantum efficiency of PSII photochemistry (Fv/Fm), CIE L*a*b* leaf colour parameters, fresh and dry biomass, and macro- and micronutrient concentrations in the edible aerial parts were determined. Foliar nutrient management significantly affected the SPAD-based relative chlorophyll status, leaf colour, edible biomass and selected mineral elements, whereas Fv/Fm was not significantly affected by treatment. CovF was associated with the highest SPAD values, darker, greener and less yellow leaves, and the highest N, Zn and Fe concentrations. Both INM-b and CovF increased fresh and dry biomass relative to the Ctrl and increased the P, K and Mn concentrations, while Ca, Mg and B were not significantly affected. Because INM-b and CovF differed in nutrient composition, formulation and nutrient supply, the present design does not isolate the specific effect of the biostimulant-containing component. Therefore, these findings should be interpreted as preliminary responses of S. napiformis to the tested foliar management strategies under pot cultivation, requiring future validation through isonutrient-, factorial- and field-based experiments.

The prehistoric and historic Greek populations have a long and glorious history and could teach us significant lessons relevant to water resources and their management. Most Greek civilizations lived in harmony with the environment, with a profound understanding of environmental sustainability. The Minoan era, considered as Pax Minoica (or Minoan peace), was a time when palaces and other living places did not have defensive walls; in that time, human rights and power without a military aristocracy developed. During that time, hydro-structures with a high degree of security, which remained in operation for millennia, were developed, most of them established in predominantly arid areas for reasons of security, protection, and public health. The study presents important elements of the development and progress of these technological achievements provided by ancient civilizations throughout the prehistoric to modern period, in the context of revealing and highlighting potential lessons to understand and address current critical issues in the management of water resources. Furthermore, the methodology used and the technological structural advancement of water works, their infrastructure durability, and early water law principles are considered. Many modern systems are designed for operational lifespans of 50–100 years, whereas several ancient Greek hydraulic structures remained functional for centuries by relying on renewable natural resources—reflecting a fundamentally different design philosophy centered on longevity and robustness. Thus, terms such as “sustainability” and “water security/safety”, first taught by ancient civilizations, need to be reconsidered and adopted again nowadays to inspire policies, strategies, and actions against the increasing challenges.

Despite a growing interest in biochar for olive orchard fertility management, little is known about its effects on nitrogen (N) dynamics and greenhouse gas (GHG) emissions in Mediterranean soils, particularly when comparing neutral (pH 6.7) and alkaline (pH 8.2) soils using farmer-accessible flame-curtain pyrolysis biochar. In this 60-day soil mesocosm study, we hypothesized that biochar amendments in fertilized soils would enhance soil N availability and potentially reduce N₂O emissions, with effects modulated by soil pH. Treatments included: control, urea fertilizer, and urea plus biochar (5% w/w). Urea fertilization significantly increased soil ammonium (NH₄⁺) and total oxidized nitrogen (NO₃⁻ + NO₂⁻) in both soils, and co-application of biochar further increased these pools, particularly in the neutral soil (NH₄⁺: + 91% and + 62% in neutral and alkaline soil, respectively). Biochar addition consistently reduced cumulative carbon dioxide (CO₂) emissions in both soils, supporting its role in stabilizing soil organic carbon. However, impacts on nitrous oxide (N₂O) emissions were soil-pH-dependent: biochar slightly reduced N₂O emissions in neutral soil, though nearly doubled N₂O emissions in alkaline soil, highlighting that biochar’s efficacy for GHG mitigation is context-specific. These findings underscore biochar’s potential to improve soil N availability and reduce carbon losses but reveal clear limitations for N₂O mitigation in alkaline soils, necessitating site-specific application strategies that explicitly consider soil pH when targeting climate benefits in Mediterranean olive production.

At the beginning of human history, surface water, especially from rivers and springs, was the most frequent water supply source. Groundwater was used in arid and semi-arid regions, e.g., eastern Crete (Greece). As the population increased, periodic water shortages occurred, which led to the development of sophisticated hydraulic structures for water transfer and for the collection and storage of rainwater, as seen, for example, in Early Minoan times (ca 3200–2100 BC). Water supply and urban planning had always been essentially related: the urban water supply systems that existed in Greece since the Bronze Age (ca 3200–1100 BC) were notably advanced, well organized, and operable. Water supply systems evolved considerably during the Classical and Hellenistic periods (ca 480–31 BC) and during the Roman period (ca 31 BC–480 AD). Also, early Indian society was an amazing vanguard of technology, planning, and vision, which significantly impacted India’s architectural and cultural heritage, thus laying the foundation for sustainable urban living and water resource management. In ancient Egypt, the main source of freshwater was the Nile River; Nile water was conveyed by open and closed canals to supply water to cities, temples, and fields. Underground stone-built aqueducts supplied Nile water to so-called Nile chambers in temples. The evolution of water supply and urban planning approaches from ancient simple systems to complex modern networks demonstrates the ingenuity and resilience of human communities. Many lessons can be learned from studying traditional water supply systems, which could be re-considered for today’s urban sustainable development. By digging into history, measures for overcoming modern problems can be found. Rainwater harvesting, establishing settlements in proximity of water sources to facilitate access to water, planning, and adequate drainage facilities were the characteristics of ancient civilizations since the ancient Egyptian, Minoan, Mohenjo-Daro, Mesopotamian, and Roman eras, which can still be adopted for sustainability. This paper presents significant lessons on water supply around the world from ancient times to the present. This diachronic survey attempts to provide hydro-technology governance for the present and future.

Since ancient times, dams have been built to store water, control rivers, and irrigate agricultural land to meet human needs. By the end of the 19th century, hydroelectric power stations arose and extended the purposes of dams. Today, dams can be seen as part of the renewable energy supply infrastructure. The word dam comes from French and is defined in dictionaries using words like strange, dike, and obstacle. In other words, a dam is a structure that stores water and directs it to the desired location, with a dam being built in front of river valleys. Dams built on rivers serve various purposes such as the supply of drinking water, agricultural irrigation, flood control, the supply of industrial water, power generation, recreation, the movement control of solids, and fisheries. Dams can also be built in a catchment area to capture and store the rainwater in arid and semi-arid areas. Dams can be built from concrete or natural materials such as earth and rock. There are various types of dams: embankment dams (earth-fill dams, rock-fill dams, and rock-fill dams with concrete faces) and rigid dams (gravity dams, rolled compacted concrete dams, arch dams, and buttress dams). A gravity dam is a straight wall of stone masonry or earthen material that can withstand the full force of the water pressure. In other words, the pressure of the water transfers the vertical compressive forces and horizontal shear forces to the foundations beneath the dam. The strength of a gravity dam ultimately depends on its weight and the strength of its foundations. Most dams built in ancient times were constructed as gravity dams. An arch dam, on the other hand, has a convex curved surface that faces the water. The forces generated by the water pressure are transferred to the sides of the structure by horizontal lines. The horizontal, normal, and shear forces resist the weight at the edges. When viewed in a horizontal section, an arch dam has a curved shape. This type of dam can also resist water pressure due to its particular shape that allows the transfer of the forces generated by the stored water to the rock foundations. This article takes a detailed look at hydraulic engineering in dams over the millennia. Lessons should be learned from the successful and unsuccessful applications and operations of dams. Water resource managers, policymakers, and stakeholders can use these lessons to achieve sustainable development goals in times of climate change and water crisis.

According to FAO, water scarcity is now affecting all five continents and is expected to intensify in the coming years as the water demands of the growing population increase and the impacts of climate variability become more pronounced. The existing unevenness of water resource availability and insufficient investment in relevant infrastructure have forced the water sector to recognize the importance of nonconventional water resources (NWR) in planning for a sustainable water future. The purpose of this review is to highlight the available and potentially available NWR and to discuss the future application of these water sources.

Origanum dictamnus L. (Lamiaceae), a local endemic plant of Crete (Greece), creates polysaccharide-containing subcuticular compartments presenting biological activity against phytopathogenic fungi, and, among others, significantly affects the fungal cell wall polysaccharides. This field study introduces a fertilization scheme for O. dictamnus, which was developed and refined to optimize the yield as well as critical herbal quality aspects. Five fertilization schemes were investigated, based on a polysaccharide-based Integrated Nutrient Management (INM), a mixture of conventional inorganic fertilizers (ChF) and two biostimulants (not algae) via foliar and soil application. Plant growth, together with leaf chlorophyll fluorescence and color (SPAD meter, DA meter, Chroma Meter) were determined. The leaf content of chlorophyll, three critical antioxidant compounds (carotenoids, flavonoids, phenols) and nutrients were also assessed. Considering all three antioxidants together, the enhanced efficiency, non-toxic, water-soluble, polysaccharide-based INM by foliar application was the most stimulatory scheme, playing an important role in plant growth and development. The present field study provides, for the first time, baseline fertilization data improving key herbal quality features in O. dictamnus and unravels the attainment of high antioxidant properties. The latter may be exploited in favor of its further utilization as a raw material for tea preparation, medicinal purposes, natural food flavoring and/or food preservative.

Due to the combined climate and biodiversity crisis, the sustainable utilization of phytogenetic resources stands as a one-way alternative, while nutrient management strategies are gaining an increasing role in agriculture. Building on previous studies regarding the Endangered local endemic of Crete (Greece) Carlina diae (Asteraceae), with medicinal and ornamental value, this investigation focused on its pilot cultivation and fertilization (foliar or soil application). Foliar application comprised inorganic fertilization (conventional) or integrated nutrient management (INM). Soil application consisted of conventional inorganic fertilizers, biostimulants, or INM with biostimulants. Above-ground biomass content of nutrients, leaf chlorophyll fluorescence, and color parameters (SPAD meter, DA meter, Chroma Meter) were estimated. The leaf chlorophyll content, three key antioxidant compounds, and nutrient titers were also determined. The fertilization scheme did not influence plant growth and visually perceived quality (leaf color and shape). Notably, foliar INM fertilization increased biomass partitioning to inflorescences (harvestable organs for either medicinal or ornamental purposes) and decreased tissue water content (facilitating processing). Considering all three antioxidants together, INM with biostimulant appeared the optimum scheme, being associated with the highest (carotenoids, phenolics) or the second highest (flavonoid) content. In C. diae, therefore, INM fertilization was optimal for upgrading yield (foliar) and herbal quality in terms of antioxidant profile (INM with biostimulant), which might be embraced as an eco-friendly approach for high-quality yields.

Herein, we applied DNA barcoding for the genetic characterization of Sideritis syriaca subsp. syriaca (Lamiaceae; threatened local Cretan endemic plant) using seven molecular markers of cpDNA. Five fertilization schemes were evaluated comparatively in a pilot cultivation in Crete. Conventional inorganic fertilizers (ChFs), integrated nutrient management (INM) fertilizers, and two biostimulants were utilized (foliar and soil application). Plant growth, leaf chlorophyll fluorescence, and color were assessed and leaf content of chlorophyll, key antioxidants (carotenoids, flavonoids, phenols), and nutrients were evaluated. Fertilization schemes induced distinct differences in leaf shape, altering quality characteristics. INM-foliar and ChF-soil application promoted yield, without affecting tissue water content or biomass partitioning to inflorescences. ChF-foliar application was the most stimulatory treatment when the primary target was enhanced antioxidant contents while INM-biostimulant was the least effective one. However, when the primary target is yield, INM, especially by foliar application, and ChF, by soil application, ought to be employed. New DNA sequence datasets for the plastid regions of petB/petD, rpoC1, psbK-psbI, and atpF/atpH were deposited in the GenBank for S. syriaca subsp. syriaca while the molecular markers rbcL, trnL/trnF, and psbA/trnH were compared to those of another 15 Sideritis species retrieved from the GenBank, constructing a phylogenetic tree to show their genetic relatedness.