Search

Cover crops are multifunctional, and contribute to improving soil properties and reducing environmental impact compared to no-cover crops, thus could provide multiple soil, agricultural, and environmental benefits, and they are recognized as a valid strategy for the achievement of sustainable agriculture. However, cover crops' impacts on subsequent cash crops and soil characteristics are dependent on several factors, such as pedoclimatic conditions, cover crop species, agricultural practices, method of termination, and irrigation management. The fact that cover crops are never applied as a single practice in the real agricultural sector, but are instead combined with other factors or agricultural practices, deeply affects their performance, but the scientific literature nevertheless keeps considering the use of cover crops alone. Moreover, the potential outcomes of cover crops that encompass other factors or agricultural practices affecting soil quality, weed control, and cash crops are still unclear. Additionally, cover crops are still poorly use in the Mediterranean type of climate. Therefore, this study reviewed the scientific literature to identify the most relevant factors or agricultural practices driving cover crops' performance, and to outline future fields of investigation looking towards promising sustainable agriculture in Mediterranean areas with a view to minimizing the competition for soil water with the cropping systems and to reduce soil degradation. Furthermore, the investigation includes multiple factors or agricultural practices that better represent the real farming system, contributing to a comprehensive understanding of their interactions with cover crops, and suggests alternative strategies for reducing yield gap while seeking to achieve agricultural sustainability. [ABSTRACT FROM AUTHOR]

Predictive weather-based models are widely used to schedule irrigation through the estimation of crop evapotranspiration. However, perceiving real-time crop water requirements remains a challenge. This research aims at field validating and exploiting a low-cost IoT soil moisture tensiometer prototype to consequently compare weather-based irrigation to soil water moisture-based irrigation in terms of yield and crop water productivity. The prototype is based on the ESP32 microcontroller and BMP180 barometric sensor. When compared to a mechanical tensiometer, the IoT prototype proved its accuracy, registering an average R2 equal to 0.8 and an RMSE range of 4.25–7.1 kPa. In a second step, the irrigation of a Romaine lettuce field (Lactuca sativa L.) cultivated under a drip system was managed according to two different scenarios: (1) using the data feed from the IoT tensiometers, irrigation was performed to keep the soil water potential between −15 and −25 kPa; (2) using the data provided by the in-situ weather station to estimate the crop water requirements. When comparing the yield, no significant difference was registered between the two scenarios. However, the water productivity was significantly higher, registering a 36.44% increment in scenario 1. The experiment highlights the water-saving potential achievable through real-time monitoring of soil moisture conditions. Since it is a low-cost device (82.20 USD), the introduced prototype facilitates deploying and managing a fleet of sensors for soil water potential live mapping. [ABSTRACT FROM AUTHOR]

Agrivoltaics, a system combining the production of agricultural crops and solar energy on the same land area, offers a potential solution to land use competition between different sectors. However, concerns have been raised regarding the impact of shade on plant growth under Agrivoltaic Systems (AVSs). Numerous studies have explored the effects of AVSs shading on agricultural crops. However, most of these studies focused on shade-tolerant crops, leaving a gap in the understanding of how these systems affect shade-intolerant crops. To this end, this study was conducted in Bari, southern Italy, using two types of AVSs: conventional (Con) and semi-transparent (ST) panels. The objective was to assess the impacts of the different levels of shading on the tomato yield and fruit quality. Tomato cultivation occurred between May and August under various conditions: Con panels, ST panels, and Open Field. The results revealed that soil temperature decreased under both AVSs compared to in the open field conditions. However, the significant reduction in photosynthetically active radiation (PAR), up to 43% in ST and 67% in Con, led to yield reductions ranging between 28% and 58% in ST and Con, respectively. Nonetheless, AVSs demonstrated their potential to reduce irrigation water demand by over 15% in ST and more than 20% in Con. Interestingly, the AVSs reduced fruit size but improved certain fruit quality attributes, such as titratable acidity, which is closely correlated with fruit flavour. These findings highlight the challenges of cultivating shade-intolerant crops under AVSs in a Mediterranean climate, while temperate, dry conditions may offer more favourable prospects for agricultural production. [ABSTRACT FROM AUTHOR]

Irrigated agriculture is threatened by soil salinity in numerous arid and semiarid areas of the world, chiefly caused by the use of highly salinity irrigation water, compounded by excessive evapotranspiration. Given this threat, efficient field assessment methods are needed to monitor the dynamics of soil salinity in salt-affected irrigated lands and evaluate the performance of management strategies. In this study, we report on the results of an irrigation experiment with the main objective of evaluating time-lapse inversion of electromagnetic induction (EMI) data and hydrological modelling in field assessment of soil salinity dynamics. Four experimental plots were established and irrigated 12 times during a two-month period, with water at four different salinity levels (1, 4, 8 and 12dSm-1) using a drip irrigation system. Time-lapse apparent electrical conductivity (σa) data were collected 6 times during the experiment period using a CMD Mini-Explorer. Prior to inversion of time-lapse σa data, a numerical experiment was performed by 2D simulations of the water and solute infiltration and redistribution process. The obtained potential spatio-temporal distributions of water content, solute concentration and bulk electrical conductivity (σb) assisted in understanding of how solute concentration and water content changes during the experiment influence σb distribution as well as optimizing the time-lapse inversion parameters for resolving σb changes in this experiment. Finally, we inverted the time-lapse field σa data and interpreted the results in terms of concentration distributions over time. Our investigation shows that EMI measurements and suitable modelling techniques allow for rapid and non-invasive investigation of spatio-temporal variability in soil salinity over large areas. Their effectiveness and relatively low cost make them appealing for management of water irrigation in salinity-threatened regions of the world. [ABSTRACT FROM AUTHOR]

Olive mill wastewater (OMW) is a compound originating from oil mills during oil extraction processes. In the Mediterranean area, more than 30 million m³ of OMW are produced each year, which represents 95-97 % of world production. Such volumes of untreated OMW are usually directly disposed of into drainage systems, water bodies (such as streams, lagoons and ponds), or else are sprinkled on soils, causing potentially severe environmental problems to soils and groundwater. There is thus a serious waste management problem related to the olive oil industry, such practices no longer being acceptable. In the case of on-land OMW disposal, characterization and identification of this contaminant in soils is a fundamental task especially with a view to maintaining the integrity and quality of agroecosystems. In recent years, soils have been extensively studied to detect contaminants by using various geophysical methods. Among such techniques, time domain reflectometry (TDR) has shown, in different contexts, evident sensitivity and resolution capability for characterizing contaminated soil sites. In order to further exploit the potential of the TDR technique, in the present study we conducted a series of laboratory-controlled tests to explore how OMW influences the dielectric response of contaminated soils. The research led to the development of an empirical dielectric model to estimate the presence of OMW in variably saturated-contaminated soils with different textures and pedological features. [ABSTRACT FROM AUTHOR]

This paper mainly aims to illustrate an irrigation management tool to simulate scheduling of district-level water needs over the course of an irrigation season. The tool is mostly based on a daily model for simulating flow of water (and solutes) in heterogeneous agri-environmental systems (called FLOWS-HAGES). The model produces information on the daily evolution of: soil water contents and pressure potentials in the soil profile; water uptake and actual evapotranspiration; stress periods for each crop; return fluxes to the groundwater and their quality in terms of solute concentrations (e.g., nitrates). FLOWS-HAGES provides a daily list of hydrants to be operated according to water or crop-based criteria. The daily optimal sequence of hydrant use may thus be established by passing the volumes to be delivered on to the model for simulating the hydraulics of the irrigation network, in order to ensure that the discharges flowing inside the network of distribution pipes are delivered under optimal pressure head distribution in the system. All the above evaluations can be carried out in a stochastic framework to account for soil heterogeneity and climate changes. To illustrate the potential of FLOWS-HAGES, a case study was considered for a selected sector of the Irrigation District 10 in the “Sinistra Ofanto” irrigation system (southern Italy, Apulia region). In a 139 ha area (Sector 6 of the Irrigation District), soil profiles were analyzed for characterization of hydraulic properties variability. Hydraulic properties were determined by a combination of field and laboratory measurements. Model simulations were validated by comparing soil water storage simulated and measured by a sensor based on electromagnetic induction technique. Irrigation water volumes and frequency calculated by the model were compared to the volumes actually supplied by the farmers. Compared to the farmers behavior, the model simulates more frequent irrigations with lower irrigation volumes. Finally, some indexes of irrigation performance were calculated for each farm under study. The resulting maps provide useful information on the spatial distribution of farmer behavior, indicating the abuse or underuse of water as well as the fraction of the water lost by drainage following the irrigation method applied. [ABSTRACT FROM AUTHOR]

The term non-aqueous phase liquid (NAPL) refers to a group of organic compounds with scarce solubility in water. They are the products of various human activities and may be accidentally introduced into the soil system. Given their toxicity level and high mobility, NAPLs constitute a serious geo-environmental problem. Contaminant distribution in the soil and groundwater entails fundamental information for the remediation of polluted soil sites. The present research explored the possible employment of time domain reflectometry (TDR) to estimate pollutant removal in a silt-loam soil that was primarily contaminated with a light hydrocarbon and then flushed with diverse washing solutions. Known mixtures of soil and NAPL were prepared in the laboratory to achieve soil specimens with diverse pollution levels. The prepared soil samples were repacked into plastic cylinders and then placed in testing cells. Washing solutions were then injected upward into the contaminated sample, and both the quantity of remediated oil and the bulk dielectric permittivity of the soil sample were determined. The above data was also used to develop a dielectric model (the α mixing model) which permits the volumetric NAPL content (θNAPL) within the contaminated sample to be determined and quantified during the different decontamination stages. Our results demonstrate that during a decontamination process, the TDR device is NAPL-sensitive: the dielectric permittivity of the medium increases as the NAPL volume decreases. Moreover, decontamination progression can be monitored using a simple (one-parameter) mixing model. [ABSTRACT FROM AUTHOR]

This paper deals with the issue of monitoring the horizontal and vertical distribution of bulk electrical conductivity, σb, in the soil root zone by using Electromagnetic Induction (EMI) sensors under different water and salinity conditions. In order to deduce the actual distribution of depth-specific σb from EMI depth-weighted apparent electrical conductivity (ECa) measurements, we inverted the signal by using a regularized 1D inversion procedure designed to manage nonlinear multiple EMI-depth responses. The inversion technique is based on the coupling of the damped Gauss-Newton method with truncated generalized singular value decomposition (TGSVD). The ill-posedness of the EMI data inversion is addressed by using a sharp stabilizer term in the objective function. This specific stabilizer promotes the reconstruction of blocky targets, thereby contributing to enhance the spatial resolution of the EMI reconstruction. Time-Domain Reflectometry (TDR) data are used as ground-truth data for calibration of the inversion results. An experimental field was divided into four transects 30 m long and 2.8 m wide, cultivated with green bean and irrigated with water at two different salinity levels and using two different irrigation volumes, to induce different salinity and water contents within the soil profile. For each transect, 26 regularly spaced monitoring sites (1 m apart) were selected for soil measurements using a Geonics EM-38 and a Tektronix Reflectometer. Despite the original discrepancies in the EMI and TDR data, we found a significantly high correlation of the means and standard deviations of the two data series, especially after filtering the TDR data. Based on these findings, the paper introduces a novel methodology to calibrate EMI-based electrical conductivity via TDR direct measurements by simply using the statistics of the two data series. [ABSTRACT FROM AUTHOR]

In arid regions, the limited rainfall may frequently produce flashfloods, with large volumes of water flowing in the streambed of so called wadi basins. Appropriate wadi management may turn flashfloods into a significant water resource to be used for agricultural purposes. In larger wadi, runoff volumes may be diverted from the stream to crop fields. In smaller wadi systems the infiltration of wadi flows in alluvial-type sediments (so-called transmission losses) represents the main source of water to eventually meet crop requirements. Using rationally this water for agricultural purposes requires to understand the rainfall-runoff behaviour of the wadi basin and the related streambed storage characteristics. In this study, the hydrological behavior of a wadi basin in Egypt (Agarma basin) was assessed. A modeling approach combining a runoff model and a soil-plant-atmosphere model was used to simulate respectively the amount of water stored in the wady stream bed after a single rainfall event and the depletion of the stored water by evapotranspiration in the period between two subsequent rainfall events. The study was based on a large data set collected in two years in the Agarma sub-basin of the Wadi Kharrouba in Egypt. The database was used as input for both a surface runoff hydrological model and a soil-plant-atmosphere model to understand the behavior of the wadi in question and the potential of its stream bed for agricultural exploitation. Specifically, the model KINEROS2 was used for predicting runoff and average transmission losses (water on average stored in the porous medium of the terraces artificially developed in the stream bed) during a single rainfall event. Being an event-based model, the KINEROS model does not account for evapotranspiration or soil water movement between rainfall events. Thus, to describe unsaturated wadi bed behavior in the time intervals between two subsequent rainfall-runoff events, in this study we applied a numerical agro-hydrological model (FLOWS-HAGES - FLOw of Water and Solutes in Heterogeneous AGri-Environmental Systems)Overall, the methodology allowed to quantify the volumes of water infiltrating in the wadi alluvial beds for each rainfall event and thus the water potentially available for crops at the end of the rain season. The results confirmed the importance of having distributed water storage measurements available, in addition to basin outlet discharges, to improve model predictive capability. [ABSTRACT FROM AUTHOR]

Improved understanding of soil hydraulic parameters and determining the potential for water movement in the root zone are very important in managing scarce water and agricultural land in a sustainable manner. Direct methods are based on drilling and cause major disturbance to the natural conditions. In addition, this procedure is time-consuming, labor intensive, and expensive, given a large number of soil samples that need to be collected. Recent research has shown that how Electromagnetic induction (EMI) method allow a rapid, noninvasive, and spatially dense data for soil characterization on a large scale. However, the potential of this method has not been fully addressed in the hydrogeophsyical approach. In our study, we used the Electromagnetic Induction (EMI) method and the inversion algorithm in the monitoring of salt and water infiltration in order to investigate the potential of EMI in root zone hydraulic parameters characterization. In this regard, water and salt infiltration measurements were performed at a parcel scale using an EMI sensor (i.e. CMD mini-Explorer) and Time Domain Reflectometry (TDR) sensors during 11 irrigation events in one day. In this regard, 3 TDR probes were inserted at 3 depths: 20, 40, 60 cm and in the 4 corners of the experimental plot prior to the experiment to monitor water content and bulk electrical conductivity (σb) while EMI data were collected at the middle of the plot in two directions.The apparent electrical conductivity data (σa) was inverted to estimate σb distribution in time. In addition, an inverse procedure was applied using HYDRUS 1D to estimate the hydraulic properties through data set collected by TDR sensors and tensiometers during the experiment. The σb data inferred from the inversion of σa at depths 20, 40 and 60 were compared to the σb measured by the TDR sensors and those simulated by the HYDRUS. We also investigated the resolution of the inverse model by performing a synthetic test.The results of our study show a very strong correlation between modeled σa data and TDR measurements as well as the HYDRUS simulations revealing the potential use of EMI data and inversion process for soil hydraulic characterization. The proposed EMI measurements and modeling techniques also allowed for detecting water and salt variations. Acknowledgment Publication supported by FCT- project UID/GEO/50019/2019 - Instituto Dom Luiz [ABSTRACT FROM AUTHOR]