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Mulching of agricultural soils has been identified as a viable solution to sequester carbon into the soil, increase soil health and fight desertification; as such, it is an interesting option for carbon farming in Mediterranean areas. Models are used to project the effects of agricultural practices on soil organic carbon in the future for various soil and climatic conditions, and to help policy makers and farmers assess the best way to implement carbon farming strategies. Here, we modify the widely used RothC model to include mulching practices and their direct and indirect effects on soil organic matter input, soil temperature changes, and soil hydraulic balance. We then calibrated and validated our modified RothC (RothC_MM) using the dataset collected in a field mulching experiment described in detail in a companying article, and used the validated RothC_MM to estimate the expected soil carbon sequestration by year 2050 due to mulching for the Valencian community (Spain). Our results show that RothC_MM improved the fit with experimental data with respect to basic RothC, and was able to predict SOC and CO2 observations taken in the field, and to model the effects of mulch on soil temperature and soil water content.

Observed variations in the ground electrical conductivity (σb*) measurements obtained with EMI instruments depend on several soil proxies that infuence crop growth and development such as salinity (σe), contents of water (θw), clay (wc) and organic matter (wom) and bulk density (ρb). However, the relative contributions of all these to σb* are unknown. This knowledge is needed to improve the planning and interpretation of σb* data for precision agriculture applications. Recently, a semi-empirical model has been developed to relate σb* measurements taken with an EM38 device to σe, θw, wc, wom and ρb and also soil temperature (t). In this work this model was subjected to a global sensitivity analysis (GSA) based on the soil data obtained during two surveys carried out, one in summer and the other in autumn, in an ample irrigated area in SE Spain. On the basis of the multiple linear regression meta-models developed for the σb* measurements, these were found to linearly respond to the soil properties (R2 between 0.92 and 0.96) and thus, the GSA could be based on their standardised regression coefcients. According to these, the soil characteristics explain the following percentages of variance in σb* (PV): 30–34 (σe), 8–20 (θw), 32–47 (wc), 0.6–2.6 (wom), 5.7–7.5 (ρb) and 0.3–0.4 (t) with changes from the summer to the autumn season of − 4, − 12 and+15 in the PV explained by the most infuential properties, respectively, σe, θw and wc. The results of the GSA will help the planning and interpretation of σb* measurements for improving crop management.

The inter-row soils in conventionally run citrus orchards in Eastern Spain lose fertility, either physically, chemically, or biologically, as a consequence of machinery traffic and the use of herbicides. In order to regain inter-row soil fertility, two grass-cover management alternatives to the commonly used herbicide-kept bare management, namely, spontaneous plants and fescue, were established and left for four years until their effects on several physical, chemical, and biological parameters were monitored for two years more. The fescue ground cover exhibited lower average and maximum soil temperatures due to higher evapotranspiration rates but also higher annual soil water content on average and, additionally, higher rhizodeposition. Despite the fact that these new beneficial conditions helped enhance the soil’s biological fertility under fescue, the physical or chemical fertilities did not improve and neither did the organic carbon (SOC). The spontaneous plants also enhanced the biological fertility, but in this case, beneficial conditions were reflected by improvements in the chemical fertility, particularly the exchangeable potassium, and in the physical fertility by increasing the surface hydraulic conductivity and decreasing the bulk density. In the inter-rows of this citrus orchard, a seeded grass cover does not seem able to provide any soil fertility enhancement in comparison to a spontaneous one; rather the opposite. However, a lack of natural or man-driven nitrogen inputs poses a constraint to SOC gains. For this aim, the annual surface application of organic nitrogen-rich materials or even better, the fostering of N-fixing organisms would be recommended., This research was funded by the European Rural Development Fund (EAFRD), grant numbers AG_COOP_A/2018/036 and AG_COOP_A/2021/015. The participation of Enrique Peiró was funded by the Operative Program of the European Social Fund of the Valencian Community 2014–2020 and the IVIA through a specialization scholarship.

Inadequate nitrogen fertilizing practices lead to low nitrogen uptake efficiency (NUE), which increases water NO3− pollution, as well as N2O emissions to the atmosphere. In order to increase the NUE and decrease the N losses as NO3− and N2O from the soil-plant system, accurate data about optimum crop N concentrations and dry matter production throughout the growing season are still needed for many vegetables typically grown under Mediterranean climate. For this reason, several N fertilization trials were set up for globe artichoke, carrot, cauliflower, chard, chinese cabbage, early potato, leek, lettuce, onion, red cabbage, romanesco, and spinach, under the semiarid Mediterranean conditions of the Valencian Community (Eastern Spain) during several years. The fresh and dry matter weight (W), as well as the nitrogen concentration in the dry matter (%N) in both the marketable and non-marketable crop parts, was measured between 3 and 7 times throughout their respective growing seasons. The a and b coefficients of the average N dilution curve (%N = a W − b), for which all %N and W data were used, and the critical N dilution curve (%Nc = a Wc−b), for which only the minimun %N for maximum W data were used if available, in addition to the dry/fresh yield matter ratio (DM) and the harvest index (HI), were calculated for all these crops. No significant differences were observed between the average and critical N dilution curve coefficients in this work. Interestingly, the coefficients of both N dilution curves differed from the ones found in the literature with the exception of those obtained for similar cultivars, e.g., early potatoes, and under similar climatic conditions, i.e., Mediterranean. Besides, there were neither differences of DM and HI among the several N fertilization treatments. Therefore, due to the absence of changes in the N dilution curve and dry matter production coefficients for the different N supplies, all these parameters were estimated on the basis of the whole dataset, i.e., regardless of the N input. The use of the critical nitrogen dilution curve coefficients and dry matter production parameters presented in this work should contribute to better fit the N fertilizer additions to N demands of these vegetables under Mediterranean conditions, mainly, by their use through simulation models. Therefore, the NUE in horticulture should increase and the N losses as NO3− to inland and sea waters in these environments, and as N2O to the atmosphere should decrease.

The creation of flexible and high strength hydrogel materials from natural polymers as low cost and safe solid electrolytes is an area of intense research nowadays. We present a novel approach for the preparation of gelatin and chondroitin sulfate hydrogel complexes by using a simple centrifugation process. The innovative dual-bio-gel-network is able to swell and shrink upon changes on the pH and NaCl concentration. The solid bio-gels sandwiched between two macroporous carbon electrode materials are assembled in symmetric cells and their electrochemical properties are evaluated by cyclic voltammetry, galvanostatic, and impedance spectroscopy measurements. The cells exhibit areal capacitance values up to 2.74 mF cm¿2 (3.1 F g¿1) and a low resistance value of 12 Ohm cm2 for graphene electrode materials. These properties are the consequence of the successful infiltration of the solid gel inside the porous structure of the carbon electrode that boosts the charge transfer at the biopolymer/carbon electrode interphase. The results obtained may provide additional inspiration in the emerging field of bioelectronics, where biocompatible and powered systems are of the utmost importance., The authors would like to thank David Go´mez for assistance regarding scanning electron microscopy (SEM). Rebeca Herna´ndez is a member of the SusPlast platform from the Spanish National Research Council (CSIC). This study was supported by CONICET (National Scientific and Technical Research Council), ANPCyT (National Agency of Scientific and Technology Promotion, PICT 2016-1905), UNMdP (National University of Mar del Plata) and Spanish Ministry of Economy, Industry and Competitiveness (MINECO) (grants: MAT2017-83014-C2-2-P and MAT2017-88232-P). Javier Carretero-Gonza´lez acknowledges the Ramon y Cajal Fellow (RYC-2015-17722) from the Spanish Ministry of Economy, Industry and Competitiveness (MINECO)

Persimmon trees grafted on D. lotus have been found to be extensively affected by leaf necrosis in the important cropping area of Valencia (E Spain). Although this problem has been attributed to chloride toxicity, this association had not been rigorously demonstrated. In addition the chloride and salinity tolerance of persimmons grafted on D. lotus has not been characterised, and neither has the performance of this rootstock been compared to D. virginiana. Two outdoors experiments, one in pots, and another one in the field were set up and conducted for three years with trees grafted on both rootstocks. Trees in the pots experiment were arranged in five groups and irrigated with waters differing in their salt and thus, Cl−, Ca2+ and Na+ water contents. Season-end leaf contents of Na, Cl, N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn, toxicity symptoms and fruit yields were assessed. In the field experiment, one irrigation water quality was used, and just leaf chloride contents, water potential and fruit yields were evaluated. Field toxicity symptoms were reproduced in the pots experiment in the trees on D. lotus, but not on D. virginiana, with leaf chloride contents increasing with increasing irrigation water salinity. Leaf chloride contents were much higher than either sodium or boron, and significantly more correlated with toxicity symptoms. Comparing to chloride toxicity and salinity tolerance data from similar woody crops, D. lotus was classified as sensitive to salinity with, respectively, threshold ECe and slope of 1.2 dS m−1 and 22 dS−1 m. D. lotus rootstocks lend persimmon trees very lower ability to avoid chloride toxicity likely because of, on the one hand, its low soil exploration capacity, and, on the other hand, its low chloride exclusion capacity. In return, however, D. lotus lends persimmon trees more productivity, which still keeps for waters with slight-to-moderate chloride contents (3–4 mmol/L)., F. Visconti thanks the financial support received from the Spanish Ministry of Economy and Competitiveness (MINECO) through grant “Juan de la Cierva” (JCI-2011-11254) during the 2012–2015 triennium.

Early diagnosis of specific chloride toxicity in persimmon trees requires the reliable and fast determination of the leaf chloride content, which is usually performed by means of a cumbersome, expensive and time-consuming wet analysis. A methodology has been developed in this study as an alternative to determine chloride in persimmon leaves using near-infrared spectroscopy (NIRS) in combination with multivariate calibration techniques. Based on a training dataset of 134 samples, a predictive model was developed from their NIR spectral data. For modelling, the partial least squares regression (PLSR) method was used. The best model was obtained with the first derivative of the apparent absorbance and using just 10 latent components. In the subsequent external validation carried out with 35 external data this model reached r(2) = 0.93, RMSE = 0.16% and RPD = 3.6, with standard error of 0.026% and bias of -0.05%. From these results, the model based on NIR spectral readings can be used for speeding up the laboratory determination of chloride in persimmon leaves with only a modest loss of precision. The intermolecular interaction between chloride ions and the peptide bonds in leaf proteins through hydrogen bonding, i.e. N-H···Cl, explains the ability for chloride determinations on the basis of NIR spectra.

Produced water (PW) is the largest by-product of the oil and gas industry. Its management is both economically and environmentally costly. PW reuse for irrigation offers an alternative to current disposal practices while providing water to irrigators in drylands. The aim of this investigation was to evaluate the environmental effects of irrigation with PW. The SALTIRSOIL_M model was used to simulate the irrigation of sugar beet with 15 PWs of a wide range of qualities in four climates of different aridity and on four contrasting soil types. The impacts on soil salinity, sodicity and pH as well as on crop yield and drainage water salinity were estimated. Well-drained soils with low water content at field capacity (Arenosol) are less sensitive to salinisation while a relatively high gypsum content (Gypsisol) makes the soil less vulnerable to both sodification and salinisation. On the contrary, clayey soils with higher water content at field capacity and lower gypsum content must be avoided as the soil structural stability as well as a tolerable soil electrical conductivity for the crop cannot be maintained on the long-term. Soil pH was not found to be sensitive to PW quality. Drainage water quality was found to be closely linked to PW quality although it is also influenced by the soil type. The impact of drainage water on the aquifer must be considered and reuse or disposal implemented accordingly for achieving sustainable irrigation. Finally, increasing aridity intensifies soil and drainage water salinity and sodicity. This investigation highlights the importance of adapting the existing irrigation water quality guidelines through the use of models to include relevant parameters related to soil type and aridity. Indeed, it will support the petroleum industry and irrigators, to estimate the risks due to watering crops with PW and will encourage its sustainable reuse in water-scarce areas.

Persimmon cultivation is gaining importance in many semiarid areas of the world. In this chapter, existing information in the literature on persimmon water requirements and responses to variations in water supply and quality are summarized. It is concluded that persimmon water needs can be particularly high during summer, when the crop coefficient can reach values close to or even above 1.0. To cope with water scarcity, regulated deficit irrigation (RDI) has been shown as a useful technique for reducing fruit drop in persimmon trees. Late RDI strategies during fruit ripening can accelerate fruit color development resulting in earlier harvesting but with lower fruit weight. This chapter also provides important information on persimmon tree responses to salinity, along with methods to alleviate the detrimental impacts of low-quality irrigation waters on tree performance.

The melon crop is moderately sensitive to soil salinity and, as a consequence, its yield decreases under saline conditions. Nevertheless, the exposure to moderate salinity also influences the melon quality by improving it, which offers compensation to the farmer. As a consequence, in moderately salt-affected lands, like the traditional irrigation area of the ‘Vega Baja del Segura’ (Alicante, Spain), melons are being grown. In this area the modernization of the secular irrigation system through the replacement of flood by drip systems, is currently being fostered. This fact, however, is generating some controversy, due to the known salt leaching effect that flood irrigation followed by drainage makes in the soil. In this study, the effects of three irrigation systems, namely, drip (DI), subsurface drip (SDI) and flood (FI), on soil salinity and thus, on the yield and quality of the melon, were compared. According to the results, the FI system kept the soil salt levels during the growth period at 4.1 ± 0.3 dS/m, that is, significantly lower than the 4.7 ± 0.2 dS/m attained with the DI and SDI systems. Nevertheless, the DI and, overall, SDI, provided higher and more homogenous soil moisture completely counteracting the effect of salinity as revealed by the soil water potential calculations. As a result, the SDI gave 27 ± 5 Mg/ha of total yield in comparison to 23 ± 2 Mg/ha (DI) and 20 ± 6 Mg/ha (FI). Besides, the SDI system reduced the number of damaged melons, thus additionally contributing to the significant higher marketable yield of the SDI (25 ± 4 Mg/ha) in comparison to the DI (20 ± 1 Mg/ha) and the FI (19 ± 7 Mg/ha). On the contrary, in the SDI treatment the fruit soluble solids content, tritatable acidity and pulp firmness decreased a bit, however, in the sensory evaluation no differences among irrigation treatments were observed.

Summary Traditional nitrogen (N) management practices with excessive N fertilizer application and higher N losses to the environment are more widely used than the recommended best management practices (BMPs) across the nitrogen vulnerable zone (NVZ) of the Mediterranean region of Valencia. Since reported underground concentrations for this region are as high as 100 mg NO3–N L−1, nutrient managers and policy makers need quick tools that qualitatively rank N management and their respective N losses to the environment in order to implement BMPs across the region. Our hypothesis was that a new tier one GIS N index tool (GIS NIT-1), based on quantitative N mass balance and qualitative rankings, can be used to assess N management practices across the NVZ. The new GIS NIT-1 assessment tool was able to simulate N uptake, hydrology characteristics (water leaching), N dynamics and NO3–N leaching across several sites of the NVZ (P

Soil salinity is an important issue constraining the productivity of irrigation agriculture around the world. The standard method for soil salinity assessment is based on a laboratory method that is cumbersome and gives rise to limitations for data-intensive works. The use of sensors for the assessment of the apparent electrical conductivity (EC) of soils offers a way to overcome these constraints. These sensors are based on three electromagnetic phenomena, namely, electrical resistivity, electromagnetic induction, and reflectometry. Each class of sensors presents its own advantages and drawbacks. In the following chapter, these are presented along with the most popular commercial EC sensors used in nowadays agriculture, equations for the assessment of soil salinity on basis sensor measurements, some examples of application, and present and future development trends.

This article presents experimental and modeled drying kinetics of potato slices of the Desiree variety (9 × 9 × 3 mm3) in a pulsed fluid bed as a function of the air velocity, air temperature, and rotating disk velocity of the pulse generator. A statistical multifactor experimental design (23) was applied to analyze the drying process with two levels each of drying temperature, air velocity, and rotating disk velocity. The results showed that the significant factors were air temperature, air velocity, rotating disk velocity, and the binary interactions of air velocity with both the temperature and the rotating disk velocity. The simplified variable diffusivity model (SVDM) gave the least deviation for the experimental data. The effective diffusivity values determined in this work are similar to those reported in the literature.

Diospyros lotus L. is advantageously used as rootstock for Diospyros kaki L. cv. “Rojo Brillante” in most plantations of Eastern Spain. However, one of the few drawbacks of D. lotus L. as rootstock, is the high sensitivity to soil salinity, and specifically chloride, it imparts to the scion, which is visually detected as an extensive late season leaf necrosis. Several complex mixtures of organic polymers such as calcium protein hydrolysates (CPH) have been recommended to counteract salt stress on plants. Nevertheless, the effects of these commercial complex products on tree crops, are not usually rigorously studied, nor satisfactorily explained. The effects on soil and plant of the addition of a commercial CPH in the irrigation water of a D. kaki L. cv. “Rojo Brillante” plantation grafted on D. lotus L. were studied during two successive seasons. Soil salinity and chloride contents, significantly, but slightly, increased in CPH treated subplots, while at the same time leaf chloride contents decreased. These effects suggest a lower chloride plant uptake in CPH treated subplots. The lower chloride uptake in CPH treated trees was accompanied by less leaf necrosis, and also lower leaf water potential. However, the yields of CPH treated and non-treated trees were statistically non-different. The build-up of compatible solutes, mainly proline and glycine betaine, in addition to the biosynthesis of salt-stress-response proteins, which would have been stimulated by the CPH, could explain the observed effects. However, the likely biosynthesis of all these substances may have drawn plant resources from fruit development, thus explaining why yields were the same in treated and non-treated subplots despite the trees in treated subplots showed better adaptation to soil salinity.

Irrigation in semi-arid areas can be optimally scheduled using models that maximize accuracy while minimizing data requirements. In this work, the validation of the one-dimensional transient-state SALTIRSOIL_M model able to monthly simulate the soil water content (θ), downward water flux (D), and the electrical conductivity in the saturation extract (ECe) is presented. The θ and the ECe were monthly monitored at 15 and 45cm depth in a plot in commercial production of globe artichoke under semi-arid climate and drip-irrigation in SE Spain during the 2011-2012 growing season. Data on water quality, weather, irrigation management, crop development and soil were also collected and used to simulate the θ, D, and ECe throughout the growing season at both depths with the SALTIRSOIL_M model. Reference and simulations of θ and D reasonably agreed with one another at both depths. ECe at 45cm depth was estimated correctly enough by the model but was underestimated at 15cm depth. The higher concentrations of nitrate, potassium, and hence other cations, which were observed at 15cm as a consequence of fertilization could explain this. The model was subsequently used to estimate the optimum water management in the plot. Use of 325-450mmyr-1 instead of 694mmyr-1, and by means of evenly distributed pulse irrigations instead of continuous ones, would have met the crop evapotranspiration requirements while avoiding excessive drainage, and maintaining soil salinity well below damaging values. © 2014 Elsevier B.V., This work has been performed thank to projects CGL2009-14592-C02-01 and CGL2009-14592-C02-02, program “Juan de la Cierva” (F.Visconti) and scholarship BES-2010-036515 (D. Martínez), all funded by the Ministerio de Ciencia e Innovación from the Government of Spain, and program Val i+d (F. Visconti), funded by Generalitat Valenciana.

Capacitance sensors such as Decagon 10HS and 5TE are increasingly used for soil water content (θ) estimation. However, their reliability and limitations in clayey soils irrigated with saline waters have not been completely characterized under field conditions. Four levels of soil water content were combined with six levels of soil salinity in twenty-four pots to assess the performance of both sensors in a wide range of soil salinities. A simplified power-law dielectric mixing model was calibrated in the laboratory to estimate the θ of a clay loam soil from the measurements of apparent dielectric permittivity (e{open}b) performed with both sensors. The calibrated equation was subsequently validated for the estimation of θ at two depths in six irrigated salt-threatened soils with clayey textures in SE Spain. The 10HS sensor provides higher estimations of e{open}b than the 5TE. Besides, the 5TE sensor was more sensitive to soil salinity. Consequently, a different calibration was carried out for each sensor. When all the soil salinity treatments were included in the calibrations, the results were poor. However, for soil apparent electrical conductivities below 1.7dSm-1 the 5TE sensor could be calibrated with low prediction errors, and with the calibration parameters b0 and b1 very close to their characteristic values in clayey and mineral soils. In field testing, the 5TE sensors calibrated with the obtained equation provided average correct estimations with an error of ±0.05m3m-3. On the contrary, the 10HS sensor overestimated the soil water content by 0.07m3m-3 on average. The proposed simple calibration equation for the 5TE sensor can be reliably used under field conditions to estimate θ of irrigated clayey soils up to an apparent electrical conductivity of 1.7dSm-1. © 2013 Elsevier B.V., The funding for this work was provided by the Spanish Ministerio de Ciencia e Innovación through projects CGL2009-14592-C02-01 and CGL2009-14592-C02-02, and program “Juan de la Cierva” (F. Visconti) and scholarship BES-2010-036515 (D. Martínez), and Generalitat Valenciana through program Val i+d (F. Visconti). We thank the two anonymous reviewers and joint editor-in-chief for their constructive comments that improved the article.

Soil acidification is a process of degradation that becomes more pronounced as a result of various human activities, but can be controlled through appropriate soil management. Calcium, magnesium and phosphorus deficiencies along with aluminium (Al) toxicity are considered the major constraints to plant growth in acid vineyard soils. The main aim of this work was to develop a model for liming amendment recommendation in acid vineyard soils using two liming materials, dolomite and sugar foam. These were used at three doses: 900, 1800 and 2700kgha(-1) of calcium carbonate equivalent (CCE). Seven soil properties, namely pH in water, pH in 1M potassium chloride (KCl), phosphorus content, base saturation, calcium, magnesium, potassium and aluminium exchangeable contents, were monitored at two soil depths (0-30 and 30-60cm) during 3 years. The association among the soil properties, and with the soil acidity, was investigated through principal component analysis. This resulted in the selection of the aluminium saturation in effective cation exchange capacity (Al%ECEC) as the soil property to be modelled. According to the results of a subsequent analysis of variance (ANOVA), the Al%ECEC strongly depends on the dose (in CCE content) of the liming material independently of its dolomite or sugar foam nature. Besides, the dose effect is different depending on the soil depth and the sampling time. As a result, two quadratic models, one per soil depth and for the time of leaf drop stage, have been proposed to make liming recommendations in acid vineyard soils. These quadratic empirical models are comparable with the known linear Cochrane model using an f value between 1.5 and 2 in the range of doses studied, i.e. able to drop the exchangeable aluminium down to 50%. However, the models proposed in this work further provide (i) different dose recommendations for the arable and deeper soil layers, and (ii) confidence intervals for minimum and maximum additions of liming materials and, specifically, for these important soils dedicated to the growing of vines under Mediterranean conditions.

Aluminium toxicity has been recognized as one of the most common causes of reduced grape yields in vineyard acid soils. The main aim of this study was to evaluate the effect of two liming materials, i.e. dolomitic lime and sugar foam, on a vineyard cultivated in an acid soil. The effects were studied in two soil layers (0-30 and 30-60 cm), as well as on leaf nutrient contents, must quality properties and grape yield, in an agricultural soil dedicated to Vitis vinifera L. cv. ‘Mencía’ cultivation. Data management and analysis were performed using analysis of variance (ANOVA). As liming material, sugar foam was more efficient than dolomitic limestone because sugar foam promoted the highest decrease in soil acidity properties at the same calcium carbonate equivalent dose. However, potassium contents in vines organs, including leaves and berries, seemed to decrease as a consequence of liming, with a concomitant increase in must total acidity. Soil available phosphorus also decreased as a consequence of liming, especially with sugar foam, though no effects were observed in plants. For these reasons fertilization of this soil with K and P is recommended along with liming. Grape yields in limed soils increased, although non-significantly, by 30%. This research has therefore provided an important opportunity to advance in our understanding of the effects of liming on grape quality and production in acid soils.

In the world areas under arid, semi-arid or dry subhumid climate, i.e. where potential evapotranspiration (ETp) exceeds rainfall (R), water scarcity imposes limits on agricultural diversity and productivity. Nevertheless, soils of high potential productivity are also often found under such climates, usually associated to river lowlands where fresh water proximity has allowed irrigation development to produce crops of high nutritional and economic value. It has been estimated that one sixth of world cultivated area is irrigated (AQUASTAT, 2008). What is more important, one third of world agricultural production comes from irrigated lands, and this fraction is going to significantly increase in the upcoming years (Winpenny, 2003). The main restriction to meet all of the soil productive potential of areas where ETp exceeds R is, in addition to water scarcity, soil salinity.

Process-based models could be used to predict the soil saturated extract salinity from extractable ion contents. However, a rigorous validation of such models for this purpose had not been carried out. A process-based model to predict the main inorganic ion composition, electrical conductivity, and pH of the saturated paste extract from extractable ion contents was developed step by step. The model development started from the principle of matter conservation in the soil solution as it concentrates from the 1:5 to the saturated paste extract. The need to include new hypotheses in the model was studied through calculation and analysis of standardised differences between measurements and model predictions. Therefore, best estimates of saturation paste extract properties occurred after taking into account the following: (i) free equilibration of the soil solution with the minerals calcite and gypsum under CO2 partial pressure of the saturated paste; (ii) further equilibration of the soil solution with the exchange complex; and (iii) determination of salt contents within the diffuse double layer (DDL) of the soil colloids, i.e. the anion exclusion. The last was necessary because the extracts where the determination of soil extractable anions (1:5 extracts), cations, and cation exchange capacity (CEC) were carried out were separated from their suspensions through centrifugation. Therefore, the reliable prediction of soil saturated paste extract salinity demands data on soil extractable ion contents, CEC, and the quantification of salts within the DDL. © 2012 CSIRO.

SALTIRSOIL (SALTs in IRrigated SOILs) is a model for the medium to long term simulation of soil salinity in irrigated, well-drained lands. Once the algorithms were verified, the objective of our study was to validate SALTIRSOIL under one of several water quality and management scenarios in Mediterranean agriculture. Because drip and surface are the most common irrigation systems in irrigated agriculture in Valencia (Spain), the validation was performed with climate, soil, irrigation water (composition and management) and crop (species and management) information from an experimental plot surface irrigated with well water and planted with watermelon that has been monitored since the late spring of 2007. To carry out the validation, first we performed a global sensitivity analysis (GSA). Second, we compared simulated soil saturation extract composition against measured data. According to the GSA, SALTIRSOIL calculations of soil salinity seem to be most affected by climate (rainfall and evapotranspiration) with 60% of explained soil salinity variance, water salinity with 26% of explained variance, and then irrigation with 4%. According to the closeness of the first comparisons between predictions and measurements, SALTIRSOIL does not seem to be affected by any systematic error, and as a consequence, neither inclusion of new parameters nor calibration of the others already included would be needed at least for surface irrigation. The validation of SALTIRSOIL continues under other water quality and irrigation management scenarios. © 2011 Elsevier Ltd., This work has been done in the framework of projects CGL2006-13233-CO2-01 and CGL2006-13233-CO2-02. The authors acknowledge the Ministerio de Educación y Ciencia from Spain their financial support. F. Visconti also thanks the Generalitat Valenciana for its financial support through a grant in the framework of project GV 0461/2006., Ministerio de Educación y Ciencia (España), Generalitat Valenciana

12 páginas, 13 figuras, 5 tablas., The knowledge of the soil saturated hydraulic conductivity (Ks) is essential for irrigation management purposes and for hydrological modelling. Several attempts have been done to estimate Ks in base of a number of soil parameters. However, a reliable enough model for qualitative Ks estimation based on the expert assessment of field characteristics had not been developed up to date. Five field characteristics, namely macroporosity (M), stoniness (S), texture (T), compaction (C) and sealing (L), in addition to tillage (G) were carefully assessed according to three classes each, in 202 sites in an agricultural irrigated area in Eastern Mediterranean Spain. After the evaluation of field characteristics, a single ring infiltrometer was used to determine the Ks value as the solution of the infiltration equation when the steady state was reached. The distribution of the Ks was assessed and five classes with 10-fold separations in class limits were defined accordingly. The relationships among site characteristics and Ks were analyzed through a correspondence analysis (CA). Next, an ordered logistic regression model (OLRM) for the prediction of the Ks class was developed. The CA revealed that, though tightly related, the set of six site characteristics should not be simplified into a smaller set, because each characteristic explains a significantly different aspect of Ks. Consequently, the OLRM was based on the six characteristics, which presented the following order of importance: L > M > G > T > C > S. According to the cross-validation of the OLRM the hit probability for the prediction of the Ks class attained an average value of 50%, which increased to 63% for the highest class of Ks. Moreover, wrong estimation of the Ks class exceeded the +-1 range only in 3% of sites. Therefore, a reliable enough assessment of Ks can be based on the expert assessment of field characteristics in combination with an OLRM., This work has been done in the framework of projects CGL2006-13233-CO2-01 and CGL2006-13233-CO2-02. The authors acknowledge the Ministerio de Educación y Ciencia from Spain their financial support. We would like to thank the two anonymous reviewers for their constructive comments.

10 páginas, 9 figuras, 6 tablas., The electrical conductivity of the water within the soil pores (ECp) measured with the WET sensor, appears to be a reliable estimate of soil salinity. A methodology combining the use of the WETsensor along with geostatistics was developed to delimit and evaluate soil salinity within an irrigated area under arid to semiarid Mediterranean climate in SE Spain. A systematic random sampling of 104 points was carried out. The association between ECp and the saturation-extract electrical conductivity (ECse) was assessed by means of correlation analysis. The semivariograms for ECp were obtained at three different soil depths. Interpolation techniques, such as ordinary kriging and cokriging, were applied to obtain ECp levels in the unknown places. For each one of the soil depths, a model able to predict ECse from ECp was developed by means of ordinary least squares regression analysis. A good correlation (r = 0.818, p < 0.001) between ECp and ECse was found. Spherical spatial distribution was the best model to fit to experimental semivariograms of ECp at 10, 30, and 50cm soil depths. Nevertheless, cokriging using the ECp of an adjacent soil depth as an auxiliary variable provided the best results, compared to ordinary kriging. An analytical propagation-error methodology was found to be useful to ascertain the contribution of the spatial interpolation and ordinary least squares analysis to the uncertainty of the ECse mapping. This methodology allowed us to identify 98% of the study area as affected by salinity problems within a rooting depth of 50 cm, with the threshold of ECse value at 2 dS m–1. However, considering the crops actually grown and 10% potential reduction yield, the soil-salinity- affected area decreased to 83%. The use of sensors to measure soil salinity in combination with geostatistics is a cost-effective way to draw maps of soil salinity at regional scale. This methodology is applicable to other agricultural irrigated areas under risk of salinization., This article is a result of a research project GV 0461/2006 funded by Conselleria de Agricultura Pesca i Alimentacio of Valencian Community. We also thank the anonymous reviewers for their fruitful comments.

Ponencia presentada en el 6th International Conference on Sensitivity Analysis of Model Output celebrado en Milan (Italia) del 19 al 22 de julio de 2010, SALTIRSOIL is a model for the prediction of soil salinity, sodicity and alkalinity in irrigated well-drained lands. These three characteristics are respectively assessed through the electrical conductivity and the sodium adsorption ratio of the soil saturation extract (ECse and SARse), and the pH of the soil saturated paste (pHsp). A global sensitivity analysis (GSA) was carried out to ascertain what input variables are more influential on these three outputs. The standardised regression coefficients of the linear regression analyses were used to calculate sensitivity measures. The irrigation water quality represented by ECiw and SARiw is the most influential factor on salinity and sodicity calculation, i.e. ECse and SARse respectively, while the carbon dioxide partial pressure so is on alkalinity (pHsp). Next there are the variables featuring the soil water balance: rainfall, average annual basal crop coefficient and reference evapotranspiration., The authors thank the Spanish Ministry of Science and Innovation for their financial support through projects CGL2006-13233-CO2-01 and CGL2006-13233-CO2-02. Fernando Visconti also thank the Valencian local government for a research scholarship in the framework of grant UCAM 2005020112.

11 páginas, 7 figuras, 7 tablas., Many empirical equations have been developed to predict the properties of saturation extracts, primarily electrical conductivity, from the properties of soil water extracts of 1 to 5 ratio. Soil water 1:5 extracts are more rapidly and reproducibly prepared than saturation extracts. However, the electrical conductivity of saturation extracts (ECse) is the benchmark to assess soil salinity. Analysis of the information provided by the electrical conductivity of soil 1:5 extracts (EC1:5) is a prerequisite to guide equation development and to use EC1:5 for soil salinity assessment. A total of 135 soil samples were taken from 39 sites at up to four different depths per site, down to a maximum depth of 95 cm in an irrigated agricultural area in SE Spain. Soil 1:5 extracts obtained from each sample were analysed for twelve chemical properties: concentration of sodium, ammonium, potassium, magnesium, calcium, chloride, nitrite, nitrate, sulphate, alkalinity and electrical conductivity. A principal component analysis (PCA) was applied to the correlation matrix of the log-transformed data set. The equilibrium status of 1:5 extracts with regard to gypsum was assessed with the chemical speciation programme SALSOLCHEMIS. The soil gypsum content was determined by using an adaptation of the classical method of total dissolution of soil gypsum, adequate to determine low gypsum contents, i.e. lower than 2%. Three principal components, accounting for 82% of the variance in the correlation matrix, were retained after eigenvector extraction. The first component accounted for 53% of the variance and was interpreted as representing the extract salinity due to gypsum dissolution. The second component accounted for 16% of the variance and was interpreted as representing the component of the extract salinity due to salts more soluble than gypsum, such as sodium and chloride salts. The information about soil salinity is split in two components in the 1:5 extracts, which are not easily resolved, whereas only one salinity component was obtained in the saturation extracts. The EC1:5 is a reliable property to estimate ECse, with a 95% confidence interval of ±1.2 dS m−1, only when it is lower than 1 dS m−1. When EC1:5 is higher than 2.4 dS m−1 it could also be reliably used to estimate soil salinity only if the 1:5 extract is gypsum-saturated, which is highly probable when the soil gypsum content is higher than 1.5%, or when the saturation extract is not gypsumsaturated, situation which happens when soil gypsum content is lower than 0.2%. When the EC1:5 is between 1 and 2.4 dS m−1, it provides poor information about the ECse, which could be between 4 and 14 dS m−1 unless the soil gypsum content is negligible, i.e. lower than 0.2%. The usefulness of the EC1:5 to estimate soil salinity can be extended when it is used in conjunction with an estimate of soil gypsum content. The development of more than one equation to estimate ECse from EC1:5 depending on soil gypsum content is recommended., We thank the Conselleria de Medi Ambient from the Generalitat Valenciana for funding this research through project GV 0461/2006. We would also like to thank the two anonymous reviewers, and editor-in-chief for their fruitful comments and indications, which improved the article.

10 páginas, 6 figuras, 6 tablas., Calcite equilibrium characterisation of soil solutions is needed in order to provide soil salinity modellers with reliable solubility constants in solutions where the hypothesis of equilibrium can be accepted. A total of 134 soil samples were taken from 39 sites at 2, 3, or 4 depths per site, down to a maximum depth of 95 cm, during a survey in the irrigated agricultural area of the Segura River Lowland (SE Spain). Soil saturation extracts obtained from each sample were analysed for thirteen chemical properties: Na, NH4, K, Mg, Ca, Cl, NO2, NO3, SO4, alkalinity, chemical oxygen demand, and electrical conductivity. A principal component analysis (PCA) was then done on the correlation matrix from the log-transformed data set. Three principal components, accounting for 76% of the variance in the correlation matrix, were retained after eigenvector extraction. These components were interpreted as representing salinisation, soil superficiality as opposed to soil depth, and fertilisation status. Sodium, chloride, magnesium, calcium and sulphate concentrations were highly correlated with the first principal component and were interpreted as explaining the variance in electrical conductivity of the soil saturation extracts, and by proxy soil salinity. Alkalinity, pH, chemical oxygen demand, and nitrite were correlated with the second principal component. Nitrate, potassium and ammonium concentrations were correlated with the third principal component, and their variation in soil was independent of soil saturation extract salt content and soil depth. According to the interpretation of the second principal component, soil saturation extracts are further than the solutions in the saturated pastes from being in equilibrium with calcite. The calcite oversaturation status of soil saturation extracts is related to soil organic matter content., We thank the Conselleria de Medi Ambient from the Generalitat Valenciana for funding this research through project GV 0461/2006. We also thank the two anonymous reviewers for their fruitful comments.

We integrated an index-based attenuation factor/retardation factor (AF/RF) model into a GIS to evaluate the risk of leaching of the most frequently applied herbicides (glyphosate, diuron, diquat, bromacil, simazine, linuron, terbuthylazine, and terbumeton) used in citrus orchards of the Valencia Community, Spain. The GIS-model system was applied to a region of 33,800 ha located near Valencia City. The soil and climate data required by the model were stored in an Arc/Info GIS in which the model algorithms were integrated using the AML programming language. A graphical user interface was developed to facilitate the use of the GIS-model system. The resulting simulation maps indicate that terbumeton, bromacil, and simazine herbicides have the highest risk of leaching because of their high mobility and low Koc (32–158 mg l− 1). The remaining herbicides are strongly adsorbed by clay particles and organic matter, thus minimising the risk of leaching through the soil profile and into groundwater. The obtained ranking of the leaching potential of analysed herbicides is as follows, from highest to lowest risk: terbumeton > bromacil > simazine > terbuthylazine > diuron > linuron > glyphosate > diquat.

Soil is one of the main non-renewable natural resources in the world. In the Valencian Community (Mediterranean coast of Spain), it is especially important because agriculture and forest biomass exploitation are two of the main economic activities in the region. More than 44% of the total area is under agriculture and 52% is forested. The frequently and or semi-arid climate with rainfall concentrated in few events, usually in the autumn and spring, scarcity of vegetation cover, and eroded and shallow soils in several areas lead to soil degradation processes. These processes, mainly water erosion and salinization, can be intense in many locations within the Valencian Community. Evaluation of soil degradation on a regional scale is important because degradation is incompatible with sustainable development. Policy makers involved in land use planning require tools to evaluate soil degradation so they can go on to develop measures aimed at protecting and conserving soils. In this study, a methodology to evaluate physical, chemical and biological soil degradation in a GIS-based approach was developed for the Valencian Community on a 1/200,000 scale. The information used in this study was obtained from two different sources: (i) a soil survey with more than 850 soil profiles sampled within the Valencian Community, and (ii) the environmental information implemented in the Geo-scientific map of the Valencian Community digitised on an Arc/Info GIS. Maps of physical, chemical and biological soil degradation in the Valencian Community on a 1/200,000 scale were obtained using the methodology devised. These maps can be used to make a cost-effective evaluation of soil degradation on it regional scale. Around 29% of the area corresponding to the Valencian Community is affected by high to very high physical soil degradation, 36% by high to very high biological degradation, and 6% by high to very high chemical degradation. It is, therefore, necessary to draw up legislation and to establish the policy framework for actions focused on preventing soil degradation and conserving its productive potential. (c) 2005 Elsevier Ltd. All rights reserved.

Affordable, commercial dielectric sensors of the frequency domain reflectometry (FDR) and capacitance-conductance (CC) types estimate the dielectric permittivity (εb) and electrical conductivity (σb) of bulk soil. In this work, an equation was obtained to estimate the pore-water electrical conductivity (σp), which is closely related to the soil salinity in contact with plant roots, from εb and σb data, by combining the simplified dielectric mixing (SDM) model that relates εb to the soil volumetric water content (θ), with the Rhoades equation that relates θ and σb to σp. This equation was calibrated with measurements of εb and σb obtained with the Delta-T WET (FDR) and the Decagon 5TE (CC) sensors, in 20 pots filled with a clay loam soil and arranged as combinations of four levels of soil moisture with five levels of soil salinity. The calibrations were performed against reference θ and σp values. The σp was calculated with the chemical equilibrium model SALSOLCHEMEC and used as a more reliable reference than the electrical conductivity of the soil wetting water. For both sensors, the SDM model on the one hand, and the Rhoades equation on the other, provided the most accurate estimations using the least number of parameters regarding their respective alternatives, i.e. the third-order polynomial and the Hilhorst equation. The combined equation for estimation of σp subsequently provided root mean square deviations of 3.1 (WET) and 4.1 (5TE) dSm-1, which decreased to 1.5 and 2.6dSm-1 for θ >0.22m3 m-3, and σb 0.22m3 m-3 and σb

Optimizing water use in vineyards is crucial for ensuring the sustainability of viticulture in semi-arid regions, and this may be achieved by minimizing direct water evaporation from the soil through the use of mulching. In this context, the current study aimed at assessing the combined effects of the vine-row application of an organic mulch (vine prunings) and no-tillage under two water regimes on soil properties, plant water and nutritional status, yield and must composition of grapevine (Vitis vinifera L.) cv. Bobal grown under semi-arid conditions. For this purpose, a field experiment in a split-plot design was carried out for three years (2016–2018) in a mature Bobal vineyard located in Eastern Spain. Two soil management strategies (tillage and organic mulching with no-tillage) were assessed under two water regimes (rainfed and deficit drip irrigation) with four replications per combination. Vine responses were determined by measuring midday stem water potential, leaf nutrient concentrations, pruning weight, yield components and grape composition. Soil properties were assessed at the end of the experiment. Mulching and no-tillage positively affected vine water status under both water regimes, resulting in reductions in grape phenolic composition. Interactive effects of both water regime and soil management on water use efficiency were found. Regardless of soil management practice, irrigation increased yield and pruning weight when compared to rainfed conditions. Soil management had slight effects on vine nutritional status. At the end of the experiment, soil compaction increased and infiltration decreased as a consequence of mulching and no-tillage. Organic mulch and no-tillage improved vine water status, however, considering the final soil surface compaction and low water infiltration rate, longer-term studies are necessary to assess the sustainability of combining both practices., This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) with FEDER co-financing [grant number AGL2017-83738-C3-3] and the EU by H2020 project SHui [grant number 773903]. Cajamar and Lucio Gil de Fagoaga for facilitating the experimental field.