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Crassulacean acid metabolism (CAM) crops are important agricultural commodities in water‐limited environments across the globe, yet modelling of CAM productivity lacks the sophistication of widely used C3 and C4 crop models, in part due to the complex responses of the CAM cycle to environmental conditions. This work builds on recent advances in CAM modelling to provide a framework for estimating CAM biomass yield and water use efficiency from basic principles. These advances, which integrate the CAM circadian rhythm with established models of carbon fixation, stomatal conductance and the soil–plant‐atmosphere continuum, are coupled to models of light attenuation, plant respiration and biomass partitioning. Resulting biomass yield and transpiration for Opuntia ficus‐indica and Agave tequilana are validated against field data and compared with predictions of CAM productivity obtained using the empirically based environmental productivity index. By representing regulation of the circadian state as a nonlinear oscillator, the modelling approach captures the diurnal dynamics of CAM stomatal conductance, allowing the prediction of CAM transpiration and water use efficiency for the first time at the plot scale. This approach may improve estimates of CAM productivity under light‐limiting conditions when compared with previous methods. This work uses a mathematical description of the CAM circadian rhythm to predict CAM biomass accumulation and transpiration in the field. Results are compared with data from field experiments and predictions from the environmental productivity index for Opuntia ficus‐indica and Agave tequilana. [ABSTRACT FROM AUTHOR]

Environmental and economic sustainability of agricultural systems has to face the general decreasing trend of water resources through the adoption of strategies aimed at improving water-use efficiency. In the study, during three consecutive summer seasons, the effects of deficit irrigation (DI) treatments applied on mature orange trees [Citrus sinensis (L.) Osbeck] cv. "Tarocco Meli" were analyzed. Two different DI strategies supplying 70 and 50% of crop evapotranspiration (ETc) were compared with irrigation at the full rate of ETc; the comparisons were carried out in terms of plant physiological response, crop production, quality, and nutritional status. The orange trees became less sensitive to moderate water restrictions (DI = 70% ETc) permitting approximately 80 mm of water saving (i.e., corresponding to a threshold for water stress integral of 60 MPa) per season without any significant impact on their water status and on agronomic performances. Severe water restrictions (DI = 50%ETc) reduced fruit weight and crop production every year, with water-use efficiency values similar to those of the moderate DI (70% ETc). The study does not evidence crop mineral nutrition imbalances and yield decrease caused by mild water reductions. A moderate water restriction can be applied in commercial orange orchards because it saved water and improved fruit quality by increasing total soluble solids and titratable acidity while the fruit maturity was delayed. [ABSTRACT FROM AUTHOR]

In this study, the adaptation characteristics of orange trees, related to the application over a decade of deficit irrigation (DI) strategies, have been explored. To this purpose, the analysis of a minimal dataset composed of physiological information (stem water potential - Ψ stem and sap flow - SF measurements), yield (fruits number and weight) and qualitative parameters (titratable acidity, TA; and total soluble solids, TSS) was performed with reference to the last irrigation seasons (i.e. 2018–19). The applied irrigation treatments were the following: sustained deficit irrigation (SDI); regulated deficit irrigation (RDI); partial root-zone drying (PRD), each distributing a water deficit of about 19%, 29% and 52%, respectively, compared to the control treatment (FI) supplying the full irrigation level (100% ET c). In general, higher water use efficiencies (WUE) have been obtained in DI treatments, which guarantee greater water savings (up to 50%), without affecting yield and quality characteristics. In particular, the most stressed treatment (PRD), while reaching the lowest Ψ stem values (− 1.8 to − 2.0 MPa), as also shown by SF versus Ψ stem clusters, resulted in WUE values for yield (WUE Y), TA (WUE TA) and TSS (WUE TSS) parameters of approximately 2.6, 2.9, and 3.1 times greater than FI, respectively. Overall, this study allowed identifying the cumulative adaptation characteristics of the orange trees under study to the application of long-term DI strategies and showing that trees were able to achieve yields and qualitative features similar to those obtained with FI, even after 10 years of application of deficient irrigation regimes. • Water savings up to 53% were reached for citrus grove under deficit irrigation (DI). • Higher water use efficiencies for DI regimes than for full irrigation conditions. • Orange trees showed adaptation effects after long-term DI application. • Long-term water deficit application did not affect orange yield and quality. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experiment carried out in Southern Italy (Sicily) on the estimation evapotranspiration (ET) in pilot constructed wetlands planted with different species (Chrysopogon zizanioides, Myscanthus x giganteus, Arundo donax, Phragmites australis, and Cyperus papyrus). In the two monitored growing seasons, reference ET0 was calculated with the Penman-Monteith formula, while actual ET and crop coefficients were measured through a water balance and the FAO 56 approach, respectively. The highest average seasonal ET value was observed in Phragmites australis (17.31 mm d−1) followed by Arundo donax (11.23 mm day−1) Chrysopogon zizanioides (8.56 mm day−1), Cyperus papyrus (7.86 mm day−1), and Myscanthus x giganteus (7.35 mm day−1). For all plants, crop coefficient values showed different patterns in relation to growth stages and were strongly correlated with phenological parameters. Myscanthus x giganteus and Arundo donax showed a water use efficiency values significantly higher than those observed for the other tested species. Results of this study may contribute to select appropriate plant species for constructed wetlands located in semi-arid regions, especially when the use of reclaimed water and/or the use of aboveground biomass are planned. [ABSTRACT FROM AUTHOR]

Soon, water scarcity is expected to worsen due to several factors including the population growth and the climate change. To address this, the European Water Framework Directive (WFD) mandates an increase in the water use efficiency of agrosystems. In this context, the aim of the study was to provide a novel methodological approach, based on the use of satellite-based classification algorithms (i.e., artificial neural networks, ANN, and the Optical Trapezoid Model, OPTRAM), agro-hydrological modelling (i.e., satellite-based ArcDualK c model versus traditional FAO-56 approach) combined with different sources of agrometeorological data (i.e., ground-based versus ERA5 Land data), for mapping the irrigated crops and determining their irrigation water requirements (IWR) at the irrigation district level. The study was carried out, during the period 2019–20, in an irrigation district, named "Quota 102,50" (Eastern Sicily, Italy) and managed by the local reclamation consortium. The use of ANN and of OPTRAM allowed to obtain an accurate detection of the irrigated crops, with overall accuracy of 82 % and 88 %, respectively during 2019–20. The IWR retrieved with the ArcDualK c model and the standard FAO-56 approach were generally underestimated in comparison to the volumes supplied by the farmers. The best performance resulted when the ArcDualK c model was implemented with ERA5 Land data, with average values of coefficient of determination, residual standard error and slope of 0.99, 975.31 m3 and 0.78, respectively, during 2019–20. The outputs at the district scale compared to the data declared by the reclamation consortium resulted in overestimations in terms of both irrigated areas and IWR, with absolute errors of about 1539 ha and 1431 ha, and of about 9 106 m3 and 12 106 m3, respectively, during 2019–20. Finally, the study provided a useful methodological framework for supporting the water management authorities to better planning and monitoring the irrigation water uses under the current WFD. • Land cover maps were obtained by implementing the artificial neural networks. • The use of the Optical Trapezoid Model allowed to detect the irrigated crops. • Irrigation water requirements were estimated through agro-hydrological modelling. • The ArcDualKc model performed better than the traditional FAO-56 approach. • The best results were observed using climate reanalysis as meteorological input. [ABSTRACT FROM AUTHOR]

Deep tillage can be applied to face high-density soil horizons by improving the root system's access to deeper layers. In this sense, soil and ecosystem services related to nutrients cycling and water recharge can be improved. In this study, the spatial and temporal dynamics of soil water content (θ) were inferred using two-dimensional electrical resistivity (ER) surveys, that were applied to explore the soil profile treated by deep tillage under different citrus rootstocks (RS) implantation. A seasonal scale ER monitoring (Spring 2018, Summer 2019, and Winter 2019) was carried out at a selected study area, characterized by Ultisols and located in Southeastern Brazil. Three different citrus RS-types, represented by the varieties 'Cravo Santa Cruz lemon' (CSC), 'Sunki Tropical Tangerine' (ST), and 'Citrandarin Indio' (CI). Deep tillage was adopted before RS citrus-types planting by opening furrows and subsoiling up to 0.6 m depth. The interrows citrus plants were covered with Brachiaria decumbens (Syn. Urochloa) in all citrus RS-type plots. A native forest area ('Forest') was used as reference for all θ evaluations. The model for the ER-θ relationships was determined from measurements conducted on soil samples in the laboratory. Root water uptake (RWU), in terms of θ changes, was evaluated at the different treatments under study. The obtained results proved the suitability of ER method for identifying the ER-θ dynamics in the Ultisol profiles over time. Lower and more stable θ values were obtained in the 'Forest' and interrow areas. Among the evaluated citrus RS-types, CSC showed the highest water use efficiency due to the greatest root system development. [Display omitted] • ER is a useful technique for inferring the soil water content (θ) dynamics. • ER-θ adjusted models explain 45–80 % of the θ changes in Ultisol. • ER season-based analyses allow to compare θ dynamics under citrus rootstocks. • Greater root-water uptake (RWU) was indirectly related to lower θ. • Greater RWU was observed in CSC rootstock. [ABSTRACT FROM AUTHOR]