Management options influence seasonal CO2 soil emissions in Mediterranean olive ecosystems

Field trials were conducted at traditional Mediterranean olive agro-ecosystems grown at two locations (Italy –IT, Greece –GR). Groves were managed for many years using sustainable (S, cover crops, compost application, mulching of pruning biomass) or conventional (C) practices (e.g., soil tillage, burning of pruning residuals). The IT grove was rainfed (RAIN) while the GR was irrigated (IRR). This study examined the seasonal variation of soil CO2 emission (Rs) to explore the effect of the management options (C, S) on Rs at both sites. The second aim was to test the hypothesis that the seasonal Rs is differentially modulated by soil temperature and moisture, namely that (i) soil moisture limits Rs when it is below the lower limit of the readily available water (RAWLLim) and (ii) soil temperature above a threshold (max_T) reduces Rs even if soil moisture is non limiting. On the whole-season basis, the mean Rs rate at the rainfed site was 2.17 ± 0.06 (SE) at CRAIN and 2.32 ± 0.06 μmol CO2 m−2 s–1 at SRAIN plot, while at the irrigated site Rs was about 3.64 ± 0.11 (CIRR) and 4.05 ± 0.15 μmol CO2 m−2 s–1 (SIRR). The seasonal oscillation of Rs was consistent across locations and partitionable in three periods according to DOY (Day of Year) interval: Phase I (DOY 20–103 –GR; 20–118 -IT), Phase II (DOY 141÷257, GR; 142–257, IT) and Phase III (DOY 291–357, GR; 286–350, -IT). Pooling all the Rs data across sites and managements, max_T was ∼ 20 °C discriminating a differential response of Rs when soil moisture was < or > RAWLLim. These differential modulations exerted by temperature and moisture were integrated into a conditional model developed with a repeated random subsampling cross-validation procedure to effectively (R2 = 0.84) predict Rs. This paper mechanistically describes the interaction of the environment (soil moisture and temperature) and the management options (S, C) under various moisture conditions on Rs and would support carbon flux accounting procedures (e.g., regulating ecosystem services) tailored to the estimation of sink/source capability of traditional olive agro-ecosystem within environmental-friendly agricultural domains

How Does Agricultural Water Resources Management Adapt to Climate Change? A Summary Approach

This editorial paper takes the form of a concise report and delves into a critical and intricate issue essential for the sustainability of agriculture. It centers on the intricate relationship between agri-cultural water resource management and agronomical practices, as well as their ability to adapt to the impacts of climate change while ensuring both the quantity and quality of crop yields. Specifically, this paper serves as a synopsis of how the far-reaching consequences of climate change for water resources impact agricultural production. It also highlights primary adaptation strategies for managing agricultural water resources, as drawn from the existing literature. Such strategies are designed to counteract the potentially adverse impacts of climate change on the rural sector. Fur-thermore, this brief report offers a valuable overview of the 17 selected papers featured in this Special Issue (SI) on Water, published by MDPI. These papers serve as exemplars of cutting-edge approaches to adaptability in water resource management and resilient crop production systems, as these fields attempt to thrive in an ever-changing environmental landscape

Developing an Open-Source IoT Platform for Optimal Irrigation Scheduling and Decision-Making: Implementation at Olive Grove Parcels

Climate change has reduced the availability of good quality water for agriculture, while favoring the proliferation of harmful insects, especially in Mediterranean areas. Deploying IoT-based systems can help optimize water-use efficiency in agriculture and address problems caused by extreme weather events. This work presents an IoT-based monitoring system for obtaining soil moisture, soil electrical conductivity, soil temperature and meteorological data useful in irrigation management and pest control. The proposed system was implemented and evaluated for olive parcels located both at coastal and inland areas of the eastern part of Crete; these areas face severe issues with water availability and saltwater intrusion (coastal region). The system includes the monitoring of soil moisture and atmospheric sensors, with the aim of providing information to farmers for decision-making and at the future implementation of an automated irrigation system, optimizing the use of water resources. Data acquisition was performed through smart sensors connected to a microcontroller. Data were received at a portal and made available on the cloud, being monitored in real-time through an open-source IoT platform. An e-mail alert was sent to the farmers when soil moisture was lower than a threshold value specific to the soil type or when climatic conditions favored the development of the olive fruit fly. One of the main advantages of the proposed decision-making system is a low-cost IoT solution, as it is based on open-source software and the hardware on edge devices consists of widespread economic modules. The reliability of the IoT-based monitoring system has been tested and could be used as a support service tool offering an efficient irrigation and pest control service

A Review of HYDRUS 2D/3D Applications for Simulations of Water Dynamics, Root Uptake and Solute Transport in Tree Crops under Drip Irrigation

Orchards with tree crops are of critical importance to the global economy and to the environment due to their ability to be productive for many years without the need for replanting. They are also better adapted to extreme climatic conditions compared to other crops. However, new challenges are emerging as climate change threatens both tree production and water supply. Drip irrigation (surface and subsurface) is an irrigation method that has the potential to save water and nutrients by placing water directly into the root zone and minimizing evaporation. Many irrigation designs and strategies have been tested to best perform drip irrigation for any given soil, crop and/or climate conditions. The researchers’ need to find the optimal combination of irrigation management and design in the most economical and effortless way led to the use of comprehensive numerical models such as HYDRUS 2D/3D. HYDRUS 2D/3D is a widely used mathematical model for studying vadose zone flow and transport processes. A review of HYDRUS 2D/3D applications for simulations of water dynamics, root uptake and solute transport under drip irrigation in the four most common categories of tree crops (citrus, olive, avocado and deciduous fruit/nuts) is presented in this study. The review promotes a better understanding of the effect of different drip irrigation designs and treatments, as well as the reliability provided by HYDRUS 2D/3D in the evaluation of the above. This manuscript also indicates gaps and future challenges regarding the use of the model in simulations of drip irrigation in tree crops

A Comparison between Variable Deficit Irrigation and Farmers’ Irrigation Practices under Three Fertilization Levels in Cotton Yield (Gossypium hirsutum L.) Using Precision Agriculture, Remote Sensing, Soil Analyses, and Crop Growth Modeling

The major global challenge for the coming decades will be increasing crop production with less water consumption. Precision agriculture (PA) and variable deficit irrigation (VDI) are management strategies that help farmers to improve crop production, fertilizer’s efficiency, and water use efficiency (WUE). The effects of irrigation (IR1 = variable deficit irrigation; IR2 = farmers’ irrigation common practices) under three fertilization (Ft1, Ft2, Ft3) treatments were studied on a cotton yield, on various indicators for more efficient water and fertilizer use, and on plant growth characteristics by applying a number of new agrotechnologies (such as TDR sensors; soil moisture (SM); PA; remote-sensing NDVI (Sentinel-2 satellite sensors); soil hydraulic analyses; geostatistical models; and SM root-zone modelling 2D GIS mapping). The reference evapotranspiration was computed based on the F.A.O. Penman–Monteith method. The crop (ETc) and actual (ETa) evapotranspiration were computed using crop coefficients obtained from the remote-sensing NDVI vegetation index (R2 = 0.9327). A daily soil–water–crop–atmosphere (SWCA) balance model and a depletion model were developed using sensor data (climatic parameters’ sensors, as well as soil and satellite sensors) measurements. The two-way ANOVA statistical analysis results revealed that irrigation (IR1 = best) and fertilization treatments (Ft2 = best) significantly affected the cotton yield, the plant height, the plant stem, the boll weight, the above-ground dry matter, nitrogen and fertilizer efficiency, and WUE. VDI, if applied wisely during critical growth stages, could result in a substantial improvement in the yield (up to +28.664%) and water savings (up to 24.941%), thus raising water productivity (+35.715% up to 42.659%), WUE (from farmers’ 0.421–0.496 kg·m−3 up to a VDI of 0.601–0.685 kg·m−3), nitrogen efficiency (+16.888% up to +22.859%), and N-P-K fertilizer productivity (from farmers’ 16.754–23.769 up to a VDI of 20.583–27.957). © 2022 by the authors

Growth, photosynthesis and pollen performance in saline water treated olive plants under high temperature

© G.C. Koubouris et al., 2015. Olive cultivation in hot arid areas is hindered by the scarcity of irrigation water. The exploitation of saline water has been proposed as a solution to partially cover plant water demands. This paper presents the effects of salinity [0, 60 and 120 mM sodium chloride (NaCl)] on physiological and reproductive functions of cultivars Koroneiki and Amphissis in a closed hydroponic system. Shoot growth was markedly reduced in high salinity dose in Amphissis (−81%) and Koroneiki (−75%). The photosynthetic rate was significantly reduced at 120 mM NaCl for both cultivars, as well as chlorophyll and carotenoids content (43% and 44%, respectively). The Na+ content in all plant parts increased in both salinity doses especially in Amphissis while K concentration decreased for both cultivars. Inflorescences in Amphissis were severely damaged due to salinity. Consequently, pollen sampling and in vitro germination study was only feasible for Koroneiki. Indeed, Koroneiki pollen germination was reduced at 60 mM NaCl (−42%) and at 120 mM NaCl (−88%). Pollen tube length was also reduced by 15% and 28% for the middle and high salinity dose, respectively. The results of the present study indicate that Amphissis is more sensitive in high salinity doses compared to Koroneiki and that reproductive functions are severely affected by salinity

Growth, photosynthesis and pollen performance in saline water treated olive plants under high temperature

© G.C. Koubouris et al., 2015. Olive cultivation in hot arid areas is hindered by the scarcity of irrigation water. The exploitation of saline water has been proposed as a solution to partially cover plant water demands. This paper presents the effects of salinity [0, 60 and 120 mM sodium chloride (NaCl)] on physiological and reproductive functions of cultivars Koroneiki and Amphissis in a closed hydroponic system. Shoot growth was markedly reduced in high salinity dose in Amphissis (−81%) and Koroneiki (−75%). The photosynthetic rate was significantly reduced at 120 mM NaCl for both cultivars, as well as chlorophyll and carotenoids content (43% and 44%, respectively). The Na+ content in all plant parts increased in both salinity doses especially in Amphissis while K concentration decreased for both cultivars. Inflorescences in Amphissis were severely damaged due to salinity. Consequently, pollen sampling and in vitro germination study was only feasible for Koroneiki. Indeed, Koroneiki pollen germination was reduced at 60 mM NaCl (−42%) and at 120 mM NaCl (−88%). Pollen tube length was also reduced by 15% and 28% for the middle and high salinity dose, respectively. The results of the present study indicate that Amphissis is more sensitive in high salinity doses compared to Koroneiki and that reproductive functions are severely affected by salinity

Sustainable Agricultural Practices for Improving Soil Carbon and Nitrogen Content in Relation to Water Availability – An Adapted Approach to Mediterranean Olive Groves

<p>A field experiment was conducted in an irrigated olive orchard to determine the effects of an orchard management system consisting of increased carbon input management on spatial distribution (tree inter-row/in-row, soil depth 0–10/10–20 cm) of nitrogen and carbon in the soil as well as on some microbial properties in relation to water availability. The experiment consisted of 12 blocks (each with 4 trees covering 200 m² of land), uniform olive tree canopy size and natural vegetation, used as replications (three per treatment) in a split plot design for the following four treatments: a) spreading of olive mill compost on the soil without soil tillage, b) spreading of chopped pruning residue on the soil without soil tillage, c) combination of b + c, and d) control which received no organic materials and soil was kept free of weeds with frequent tillage and herbicide sprays. Increased soil organic matter content (SOM) (up to +80%), NO₃ N (up to +194%), and NH₄ N (up to +37%) by carbon inputs were observed in soil layer 0–10 cm. Irrigation enhanced SOM, NH₄ N, and electrical conductivity (EC) while it favored NO₃ N increase by carbon inputs. All microbial properties (Soil Basal Microbial Respiration, Soil Microbial Biomass Carbon, and Metabolic quotient) were significantly higher at 0–10 cm in comparison to 10–20 cm depth. This study suggests good agricultural management practices for optimized soil organic carbon (SOC) storage adapted to the typical Mediterranean agroecosystems.</p

Application of time-lapse electrical resistivity tomography and groundwater simulation models to monitor the transport of organic contaminants under unsaturated and saturated conditions

Production of olive oil is one of the most important activities in the Mediterranean area, particularly in Greece, which holds the third place worldwide after Spain and Italy. For every tone of produced olive oil, about 25% of liquid wastes (olive oil mill wastes- OOMWs) enriched with organic load and inorganic constituents are produced. The OOMWs are usually disposed in uncontrolled, unprotected and poorly constructed shallow evaporation ponds, causing several ecological problems such as odour, increased salinity, toxicity to soil and contamination to surface water bodies and groundwater. A pilot study area (an evaporation pond of OOMWs) has been constructed in Western Crete, at Alikianos village, very close (about 15 meters) from Keritis river. During the last decades, geophysical methods have gained popularity as efficient tools for monitoring the changes of subsurface physical properties over time and identifying the spatial distribution of pollutants. The OOMWs are mainly characterized by high electrical conductivity values and high concentration of phenolic compounds. Those characteristics of OOMWs can be used for detecting them and in particular using geoelectrical methods. In the present study, time-lapse electrical resistivity tomography (ERT) and self-potential techniques are used to map and monitor the subsurface contamination caused by OOMW. A three-dimensional finite-element model for groundwater flow and transport is developed to estimate the temporal and spatial distribution of the selected contaminant under unsaturated and saturated conditions. The resulted simulation models are verified by the obtained time -lapse two-dimensional ERT geophysical inversion images. Results of geochemical analysis of soil and liquid samples collected from two soil profiles excavated along the ERT profile have been used for calibration and validation of both simulation and geophysical results