Soil Solution Electrical Conductivity Research Articles

Assessing Soil Dynamics and Improving Long-Standing Irrigation Management with Treated Wastewater: A Case Study on Citrus Trees in Palestine

Irrigation with Treated Wastewater (TWW) is a well-known agricultural practice in Palestine. The long-term use of irrigation with TWW, a source of water and nutrients, can affect plant development, soil, and groundwater quality. Consequently, the frequency and the intervals of irrigation events should be adequately scheduled, especially when nutrients (TWW-N) cannot be separated from the water. Achieving good water quality implies its immediate reuse in irrigated agriculture. In contrast, long-term soil and groundwater quality conservation is marked by the complex mechanisms that correlate the soil, water, plant, and atmosphere. Therefore, monitoring and modeling (MMA) are combined to retrieve the soil water and nitrate fluxes and identify a proper irrigation management plan in a case study in Beit Dajan-Palestine, where a schedule adapted to conventional water was applied to a 6-year-old citrus orchard continuously irrigated with TWW. Soil nitrogen concentration and water content data were collected from March to August 2021 to calibrate the Hydrus-1D model under the (1) farmer demand (F) scenario, where irrigation volumes are delivered according to the farmer experience, and to define an optimal irrigation management strategy with TWW according to the (2) model demand (M) scenario, based on the irrigation frequency. The latter respects the allowable thresholds of soil solution electrical conductivity, σe, assuming an average soil salinity profile and estimated leaf nitrogen concentrations tolerance as reference; 2021 was taken as a calibration year to retrieve water and nitrate fluxes for 2019 and 2020. In 2021, the measured soil electrical conductivity, σe, showed no salinity risk with an average value of 1.07 dS m−1 (low salinity < 2 dS m−1) but with a leaf nitrogen deficit. Although an acceptable level of available soil nitrogen was observed (ranging between 10 and 35 mg kg−1, whereas the standard value is 10–40 mg kg−1), critical concentrations were observed in the leaves (below 1%) in scenario (F) compared to scenario (M) (ranging between 1.7 and 1.9%). The latter also showed a decrease in nitrate leaching by 33% compared to the former. Overall, the comparison between the simulated and measured soil variables shows that the 1D-Hydrus model could follow the temporal variation in the monitored data, with some overestimation of the measured data during the simulation period. The simulations demonstrate that by modulating the salt tolerance threshold, the M scenario achieved better results in terms of root water and N uptake despite the stress inevitably experienced by citrus with long-term TWW irrigation. Moreover, the optimum threshold values used to assess the soil quality and citrus response under conventional water irrigation were inadequate for TWW practices. Therefore, MMA could be an alternative strategy to schedule proper TWW irrigation.

Effects of Different Mulching Materials on Soil Salinity of a Semi-Arid Drip-Irrigated Nectarine Orchard

ABSTRACT The effectiveness of inorganic (plastic) and organic (geotextile and pine bark) mulching materials for soil salinity control as compared to the bare soil was assessed during three years in a semi-arid, drip-irrigated nectarine orchard. The soil solution electrical conductivity (ECss) was measured in 3174 samples regularly extracted with suction cups at two soil depths (20 and 40 cm) and three sampling positions (EM-emitter, EL-emitter line, and TR-tree row) during the 2010–2012 irrigation seasons. Considering all treatments, ECss increased (p < .05) with distance to emitters, both vertically (mean ECss = 4.7 dS m−1 at 20 cm and 6.3 dS m−1 at 40 cm soil depths) and horizontally (mean ECss (20 + 40 cm soil depth) = 2.9 dS m−1 at EM, 4.4 dS m−1 at EL, and 9.1 dS m−1 at TR). The monthly changes in ECss were negatively correlated (p < .01) with the monthly field-wide leaching fraction estimates. Based on the 2010–2012 mean ECss values, the effectiveness for soil salinity control of the examined treatments was (p = .05): plastic (4.2 dS m−1) = pine bark (4.6 dS m−1) < bare soil (5.8 dS m−1) = geotextile (5.9 dS m−1). Overall, due to their lower soil water evaporation rates, the plastic and pine bark materials were best suited for soil salinity control under the prevailing climatic characteristics in the study area.

Combined effects of hydrothermally-altered feldspar and water regime on cadmium minimization in rice

The accumulation of cadmium (Cd) in grains and edible parts of crops poses a risk to human health. Because rice is the staple food of more than half of the world population, reducing Cd uptake by rice is critical for food safety. HydroPotash (HYP), an innovative potassium fertilizer produced with a hydrothermal process, has the characteristics of immobilizing heavy metals and potential use for remediating Cd-contaminated soils. The objective of this study was to evaluate the HYP as a soil amendment to immobilize Cd in acidic soils and to reduce the accumulation of Cd in rice tissues. The experiment was performed in a greenhouse with a Cecil sandy loam soil (pH 5.3 and spiked with 3 mg Cd kg−1) under either flooding conditions (water level at 4 cm above the soil surface) or at field capacity. Two hydrothermal materials (HYP-1 and HYP-2) were compared with K-feldspar + Ca(OH)2 (the raw material used for producing HYP), Ca(OH)2, zeolite, and a control (without amendment). After 30 days of soil incubation, HydroPotashs, the raw material, and Ca(OH)2 increased both soil solution pH and electrical conductivity. These materials also decreased soluble Cd concentration (up to 99.7%) compared with the control (p < 0.05). After 145 days, regardless of the materials applied, plant growth was favored (up to 35.8%) under the flooded regime. HydroPotash-1 was more effective for increasing dry biomass compared with other amendments under both water regimes. HydroPotashs reduced extractable Cd in soil, Cd content in plant biomass at tillering and maturing stage, and were efficient in minimizing Cd accumulation in rice grains.

The Effects of Soil Solution Electrical Conductivity and Sodium Adsorption Ratio on Soil Liquid Limit and Soil Strength

ABSTRACT Irrigation water quality is a global agricultural management issue. High solution sodium adsorption ratio (SAR) and low electrical conductivity (EC) of irrigation waters decrease both hydraulic conductivity and aggregate stability. Little is known how solution EC and SAR affects soil mechanical properties. Three smectitic soils were treated with salt solutions made from sodium and calcium chloride that had SAR levels of 5 and 17 at solution levels between 5 and 40 millimoles charge per liter (mmolc L−1). Soil Atterberg limits were measured using Cassagrande method and penetration resistance was measured using a falling cone penetrometer. At 5 mmolc L −1, whole soil liquid limits increased from 46% to 50% on average when solution SAR levels increased from 5 to 17, whereas plastic limit did not change. When comparing the effect of increasing SAR from 5 to 17 at a salinity level of 5 mmolc L−1 on the Aberdeen soil, the water content increased at soil strengths between 0.5 and 100 kPa. Increasing soil solution SAR at low EC levels alters soil mechanical properties leading to undesirable soil qualities for agricultural production, specifically creating greater difficulty for seedling emergence and increasing the force required for tillage.

Preliminary use of a fulvic acid, as a strategy to improve water use in saline soils

An evaluation of a fulvic acid (FA) was made in a Loam soil, by selecting the best dose to achieve salt displacement under a drip emitter. In trial 1, PVC columns were filled with a loam soil and irrigated with a KCl solution of electrical conductivity (EC) of 12.5 dS m-1. Once the soil solution EC reached the value of the KCl solution, FA doses of 0, 2.1, 5.3 and 10.5 kg ha-1 were applied. The bulk electric conductivity and soil chemical properties were evaluated after 6 irrigation cycles. In trial 2, the same soil salinized with the KCl solution was placed in 0.8 m3 containers. Two irrigations treatments were performed: a control and the best FA dose from trial 1. The displacement of the salt bulb created from irrigation with a dropper in the soil profile was characterized. In trial 1, the dose of 5.3 kg ha-1 reached the lowest EC after the third irrigation. In trial 2, the selected dose reduced EC until 3.75 dS m-1 at 0.3 m depth at the third irrigation, saving 246 L of water compared to control. Additionally, the salinity bulbs were more horizontally extended in the FA treatment. Highlights: Application of FA (5.3 kg ha -1) reduced the water use by 50% compared to leaching carried out exclusively with water. The use of Fulvic acid showed to be an alternative to consider in the recovery of saline soils under drip irrigation when irrigation water is scarce. Little or not residual effect was found after the use of Fulvic acid.

Influence of heavy rainfall in 2018-2019 and submerging on some soil properties greenhouse’s in Bazian plain, Sulaymaniyah Governorate

In rain season 2018-2019 Sulaymaniyah governorate has been precluded to rainfall precipitation with very high quantities that never has been recorded since 1985 that impact on some soil properties taking samples from 80 greenhouses in (Tainal watershed, Bazian plain, Sulaymaniyah Governorate). Since in some of these greenhouse waters flood get 1.5m high and others distorted and kinds of residues has been collected in others greenhouses as well as effects of water submerging on these greenhouses soils. Taking soil samples from greenhouses from all locations that effected hardly and making analysis for some properties’ as a parameters and the results showed that the soil solution electrical conductivity (EC) decreased significantly (P&lt;0.05) in ( Location1, Location2, Location6) (1.65dsm-1,0.35dsm-1, 0.25dsm-1 ) respectively. the pH of soils decreased as the results showed (Location1, Location2, Location3) (8.06, 8.31, 7.8) respectively but not significantly, soil aggregate differences had effected significantly and changed in different locations because of removal of the sand part, silt decreased from (% 17.25) in control Location to (5.6 in Location2, 4.1in Location7) but didn’t get to the limit that could change the soil texture. Submergence soils caused decreasing significantly (P&lt;0.05) in phosphorus concentration in (Location1, Location7) (17ppm, 12ppm) respectively. The Concentration of nitrate in soil solution decreased significantly (P&lt;0.05) (Location1, Location7) (2.5mg kg-1, 14mg kg-1) respectively under the submerged condition at field capacity causing an increase in the concentration of potassium (0.743 in Location3 and 4.358 in Location4) in some locations. Sodium increased in most of the locations significantly (P&lt;0.05) (L1, L3, L5, L7) (0.378m mol-1, 0.434m.mol-1, 0.443m.mol-1, 0.643 m.mol-1) respectively otherwise, magnesium and calcium decreased in the soil solution. From the investigation some farmer record that in the study area vegetables grew better after the submerging soils.

Laboratory Calibration of TDR Probes for Simultaneous of Measurements Soil Water Content and Electrical Conductivity

ABSTRACTAccurate measurement of water content (θ), apparent electrical conductivity (ECa) of soils, and soil solution electrical conductivity (ECw) is critical for a better management of irrigation water and the effective monitoring and control of soil salinity. In this paper, we demonstrate the design and validation of an identical time domain reflectometry (TDRWO) probe for accurate and non-destructive measurements of ECw. Two calibration functions were used to determine the soil-water content by TDR. Theses relations were verified by laboratory experiment over a wide range of θ and bulk density (BD) for dune sand. The exact length and the impedance of all TDR-probes were calibrated using the WinTDR procedure. Estimates of ECw were based on θ and the bulk ECa using a special modeling approach which applies long-time TDR waveform analysis. The geometrical disposition of the matrix phase factors (τ and β) was calculated by immersing the TDR probe in sodium chloride (NaCl) solutions of different electrical conductivities in pressure cells wetted and drained with each of these NaCl solutions. The reliability of the TDRWO was validated/proven under laboratory conditions. The laboratory experiment consisted in inserting the TDR probe into a pressure cell packed with mixed sand and 2-mm sieved loam soil that was subsequently wetted and drained with different NaCl solutions at various pressure heads. The ECw estimated by TDRWO was compared to the ECw measured in the draining solutions after they stabilized in the soil porous system. The τ and β factors calculated for the ceramic disks sets were 1.991 and 4.312, respectively. In the laboratory experiments, high and therefore significant correlations (R2 = 0.986; P < .001) were found between the ECw estimated by the TDRWO and the corresponding ECw values measured in the column-drainage. These results demonstrate that the TDRWO is an instrument which allows researchers to accurately estimate soil solution salinity independently of the soil water content and the porous medium in which the TDR probe is installed. Test results showed that the TDR method has high accuracy for monitoring soil water content but is less accurate in monitoring soil electrical conductivity across a water content range of about ≤0.03cm3/cm3. Regression analysis between TDR-Volumetric water content (ϴv) and weighing method – ϴv showed good correlation with an R2 of 0.97 and 0.98 during two laboratory experiments.

Quantitative evaluation of soil ion content using an imaginary part model of soil dielectric constant

An imaginary part model of soil dielectric constant for predicting the soil salinity status was developed based on a series of relations between dielectric imaginary part and soil bulk conductivity, soil bulk conductivity and soil solution electrical conductivity, and soil solution electrical conductivity and ion contents in soil using pot trials with different soil salinity levels in the 2008 growing season. This model was calibrated and tested with data from the 2009 growing season. The results showed that the inverted values of the total concentration of salt (Sc), Cl−, and Ca2+ at low frequencies (P-band of microwave observations) from the imaginary part model fitted well with the observed values, since root mean square errors (RMSEs) were 0.34 g kg−1, 0.09 g kg−1 and 0.13 g kg−1, respectively, but the inversion effect of Na+ was relatively poor. Moreover, the Sc, Cl−, and Na+ could be well inverted at high frequencies (C-band of microwave observations), since RMSEs were minor, with values of 0.25 g kg−1, 0.02 g kg−1, and 0.15 g kg−1, respectively. The close fit between the observed and inverted values indicated that the present models could be used to estimate soil ion content quickly and reliably under different saline conditions, which, when suitable measures are taken, can be used to reduce the effects of soil salinity on crop growth.

Phosphorus availability and soybean growth in contrasting Oxisols in response to humic acid concentrations combined with phosphate sources

ABSTRACTHumic acid (HA) use can improve phosphorus (P) availability in soils with high P fixation capacity. The aim of this study was to evaluate soil P availability and soybean growth in both medium-texture (MT) and clayey (CL) Oxisols under humic acid carbon (C-HA) concentrations: 0, 5, 10, 50 and 100 mg kg−1, combined with Araxá phosphate rock (APR) and single superphosphate (SS). Mixtures of C-HA with P sources were incubated for 15 d. In sequence, the soil solution was extracted and analyzed for soil solution C (SSC), soil solution P (SSP) and soil solution electrical conductivity (EC). Soil initial resin-P and pH were determined before soybean sowing and, after harvest, shoot (SDM), root (RDM), total dry matter (TDM), soil residual resin-P and soil pH were determined. In CL fertilized with SS, the addition of C-HA increased SSP by 17%, residual resin-P by 42%, SDM, P and N accumulated in the shoot. Addition of C-HA reduced SSP and initial resin-P in MT treated with SS and increased in 18% residual resin-P in MT fertilized with APR. Effects of HA on soil attributes, soybean growth and nutritional status rely on HA concentration, soil texture and P source used.

Modelling the Impact on Root Water Uptake and Solute Return Flow of Different Drip Irrigation Regimes with Brackish Water

Water scarcity and quality degradation represent real threats to economic, social, and environmental development of arid and semi-arid regions. Drip irrigation associated to Deficit Irrigation (DI) has been investigated as a water saving technique. Yet its environmental impacts on soil and groundwater need to be gone into in depth especially when using brackish irrigation water. Soil water content and salinity were monitored in a fully drip irrigated potato plot with brackish water (4.45 dSm−1) in semi-arid Tunisia. The HYDRUS-1D model was used to investigate the effects of different irrigation regimes (deficit irrigation (T1R, 70% ETc), full irrigation (T2R, 100% ETc), and farmer’s schedule (T3R, 237% ETc) on root water uptake, root zone salinity, and solute return flows to groundwater. The simulated values of soil water content (θ) and electrical conductivity of soil solution (ECsw) were in good agreement with the observation values, as indicated by mean RMSE values (≤0.008 m3·m−3, and ≤0.28 dSm−1 for soil water content and ECsw respectively). The results of the different simulation treatments showed that relative yield accounted for 54%, 70%, and 85.5% of the potential maximal value when both water and solute stress were considered for deficit, full. and farmer’s irrigation, respectively. Root zone salinity was the lowest and root water uptake was the same with and without solute stress for the treatment corresponding to the farmer’s irrigation schedule (273% ETc). Solute return flows reaching the groundwater were the highest for T3R after two subsequent rainfall seasons. Beyond the water efficiency of DI with brackish water, long term studies need to focus on its impact on soil and groundwater salinization risks under changing climate conditions.

Treated wastewater irrigation: Soil variables and grapefruit tree performance

Soil degradation and declining tree performance following long term irrigation with treated wastewater (TWW) have been reported recently in orchards grown on clay soils. In an attempt to reverse this situation our research objectives were to quantify the effects of replacing TWW irrigation with fresh water (FW) on water uptake, water and mineral status, growth and yield of citrus trees in relation to soil physical and chemical properties. A field experiment was carried out in a commercial grapefruit orchard in a clay soil with a history of TWW irrigation. Changing irrigation water quality from TWW to FW significantly decreased soil solution electrical conductivity (EC), Na and Cl concentration, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP) and improved aggregate stability (AS) of the soil. The concentrations of Na and Cl in leaves and roots were lower in FW-irrigated trees than in TWW-irrigated ones. Fruit yield, shoot and root growth, leaf area, water status and water uptake were all significantly and favorably affected by replacing TWW with FW. Although fruit yield increased by replacing TWW with FW irrigation, it was not significantly associated with any single or group of the studied soil attributes. However, in a stepwise regression analysis a correlation was established between fruit yield and leaf Cl and soil AS. Our findings indicate that the negative effects of irrigation with TWW are (i) through damage to soil structure leading to reduced water uptake and (ii) via accumulation of Na and Cl in roots and leaves of grapefruits to toxic levels. The positive effects of alternating poor quality water (TWW) with water of high quality (FW) occur in a relatively short time span, i.e. several months to two years, thus promoting the viability of this management practice.

Soil spatio-temporal distribution of water, salts and nutrients in greenhouse, drip-irrigated tomato crops using lysimetry and dielectric methods

This work was mainly aimed at studying the spatio-temporal distribution of water content (θw), bulk (ECa) and soil solution (ECSS) electrical conductivity measured with a dielectric sensor (GS3) and a tension lysimeter (suction cup) throughout three drip-irrigated tomato crops in Mediterranean greenhouses. The mean θw (GS3) for the wet bulb was well estimated by measuring at representative positions, especially at the centre of the wet bulb. The ECSS substantially increased in the wet bulb, irrespective of the soil position, reaching relatively high values (6–7 dS m−1) in the second half of the cycles, mostly due to sodium and chloride accumulation. The mean ECSS for the wet bulb was narrowly and linearly related to that measured at any of four representative positions in the wet bulb, which presented similar seasonal dynamics and absolute values throughout most of the crops. The mean ECSS for the wet bulb can be well estimated by measuring at one of these positions, since the errors of using measurements from these positions were relatively low. The relationship between the ECSS estimated from GS3 and that measured with suction cup varied depending mostly on soil position and cropping year, but the GS3 did not generally provide accurate ECSS estimates, especially in the second half of the cycles, when salts accumulated in the soil. Despite this, measurements of ECa and ECSS from GS3 at the centre of the wet bulb might be useful for identifying tendencies or relevant salinity changes for automated irrigation systems. The solution concentration for main salts and nutrients can be fairly well monitored by sampling at any of the four representative positions of the wet bulb. However, it appears advisable to measure at the centre of the wet bulb, as samples from this position might respond faster to changes in the nutrient solution supply or the root activity, especially for very mobile elements, such as nitrate.

Prediction of Soil Solution Electrical Conductivity by the Permittivity Corrected Linear Model Using a Dielectric Sensor

AbstractIn the present study, the electrical conductivity of the soil solution (σp) was predicted using a linear model in which the bulk soil electrical conductivity (σb) effect on the apparent die...

Some physiological responses of wheat and bean to soil salinity at low matric suctions

AbstractThe effect of soil matric suction (2-33 kPa) and salinity (soil solution electrical conductivity 0.7-8 dS m−1for bean and 2-20 dS m−1for wheat) on some physiological characteristics of bean and wheat in a clay loam soil under greenhouse condition was investigated. The results showed that the leaf chlorophyll content index and potassium concentration decrease under salinity stress and increase with matric suction from 2 to 33 kPa suction for both plants. The wheat chlorophyll content index declines during the stress spell but bean chlorophyll content index remains nearly constant. The lowest values of the content of soluble sugars and the highest values of leaf proline content are observed at2 kPa matric suction (highest aeration stress) for bean and wheat. As matric suction increases from 2 to 6 kPa, the soluble sugars increases and proline content decreases significantly and then soluble sugars decreases and proline content increases until 10 kPa suction, and the soluble sugars remains nearly constant at the higher matric suctions for both plants. While the electrical conductivity effect on the soluble sugars is not significant, the values of proline content for both crop increase significantly with electrical conductivity. It was shown that the aeration stress can result in more considerable and rapid physiological responses, in comparison with salinity stress. There is a strong correlation between wheat and bean chlorophyll content index and potassium concentration under salinity and aeration stresses.

Salinity index determination of porous materials using open-ended probes

The relations among soil water content, bulk electrical conductivity and electrical conductivity of soil solution can be described by a number of theoretical and empirical models. The aim of the paper is to examine the performance of open-ended coaxial probes with and without a short antenna in determination of complex dielectric permittivity spectra, moisture and salinity of porous materials using the salinity index approach. Glass beads of 0.26 and 1.24 mm average diameters moistened to various water contents with distilled water and KCl solutions were used to model the soil material. Due to the larger sensitivity zone, only the probe with the antenna enabled determination of bulk electrical conductivity and salinity index of the samples. The relations between bulk electrical conductivity and dielectric permittivity of the samples were highly linear, which was consistent with the salinity index model. The slope of the relation between salinity index and electrical conductivity of moistening solutions closely matched the value for sand presented in literature.

Lysimetry methods for monitoring soil solution electrical conductivity and nutrient concentration in greenhouse tomato crops

In intensive agricultural systems, such as Mediterranean greenhouses, monitoring soil nutrient and salt status is essential for optimising vegetable production and minimising soil and water pollution. This work analyses the dynamics of electrical conductivity (ECSS) and nutrient concentration in soil solution collected simultaneously with various zero-tension lysimeters and a suction cup (a tension lysimeter) throughout two greenhouse tomato crops. The ECSS obtained with zero-tension lysimeters (funnel and plate lysimeter) was generally lower than that with the suction cup, irrespective of soil depth. Moreover, the soil solution concentration of potassium, calcium, magnesium, sodium, chloride and sulphate obtained with funnel lysimeter (FullStop™) was generally lower than that with suction cup throughout both cycles, while no clear differences were found for the nitrate concentration at 0.25m depth in the 2013/14 cycle or at 0.38m depth in the 2015 one. Overall, it appears that the soil solutions collected with the suction cup and the funnel lysimeter represent different soil solution status and processes. The funnel lysimeter collects freely draining soil solution, and it may therefore provide better information about the movement of elements between soil horizons, whereas the suction cup can sample soil solution from soil pores with longer residence times, especially under unsaturated flow conditions, and might represent better the available element concentrations for plant nutrition studies. The differential response found for nitrate could be due to the fact that it is a very mobile element within the soil. The soil water matric potential was slightly higher in the soil with zero-tension lysimeters throughout most of the 2013/14 cycle, and so these devices might alter soil solution movement and water and nutrient availability. On the other hand, in general, a good fit was found between the soil solution concentration of nitrate, potassium, calcium and sodium measured with a rapid analysis system (Laqua™) and that measured using the reference laboratory method. This rapid system, in combination with the suction cup, can facilitate the farmers’ control of soil nutrient and salt status.

Impact of potassium sulfate salinity on growth and development of cranberry plants subjected to overhead and subirrigation1

New recommendations in cranberry production suggest reducing overhead irrigation and the use of subirrigation as an alternative irrigation method, two strategies suspected to increase the risk of salt buildup in soil. Because very little is known about cranberry tolerance to salinity, this study was conducted to determine if deficit irrigation and subirrigation could cause salinity issues and affect plant yield. In a greenhouse, cranberry plants were submitted to eight different treatments combination from two irrigation methods (overhead irrigation and subirrigation) and four salinity levels created by increasing amounts of applied K2SO4 (125 (control), 2500, 5000, and 7500 kg K2O ha−1). Irrigation methods showed no significant difference in measured electrical conductivity of soil solution (ECss). Meanwhile, growth and yield parameters decreased significantly with soil salinity in both irrigation treatments, and an average ECss of 3.2 dS m−1 during flowering caused a 22% drop in relative photosynthetic rate and a 56% decrease in yield when compared with the control. Cranberry seems to be salt sensitive, and further work should investigate ECss levels under different field and irrigation practices to make sure that it does not reach critical levels.

Electrical Conductivity and Chemical Composition of Soil Solution: Comparison of Solution Samplers in Tropical Soils

Soil solution samplers may have the same working principle, but they differ in relation to chemical and physical characteristics, cost and handling, and these aspects exert influence on the chemical composition of the soil solution obtained. This study was carried out to evaluate, over time, the chemical composition of solutions extracted by Suolo Acqua, with the hydrophilic membrane (HM) as a standard, using soils with contrasting characteristics, and to determine the relationship between electrical conductivity (EC) and concentration of ions and pH of soil solution samples. This study was carried out under laboratory conditions, using three soils samples with different clay and organic matter (OM) contents. Soil solution contents of F−, Cl−, NO−3, Br−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+, were analyzed, as well as inorganic, organic, and total C contents, pH, and EC, in four successive sampling times. Soil solution chemical composition extracted by the Suolo Acqua sampler is similar to that collected by the HM, but the Suolo Acqua extracted more Na+ and soluble organic C than the HM solution. Solution EC, cation and anion concentrations, and soluble C levels are higher in the soil with greater clay and OM contents (Latossolo and Cambissolo in this case). Soil solution composition varied over time, with considerable changes in pH, EC, and nutrient concentrations, especially associated with soil OM. Thus, single and isolated sampling of the soil solution must be avoided, otherwise composition of the soil solution may not be correctly evaluated. Soil solution EC was regulated by pH, as well as the sum of cation and anion concentrations, and the C contents determined in the soil liquid phase.

Genetic Algorithm Applying to Calculate the Great Wall Soil Water Electrical Conductivity

In this paper, we report a simple but effective algorithm to estimate the undetermined coefficients in the formula of soil water electrical conductivity value by the soil apparent electrical conductivity method. By doing so, the coefficients can be accurately obtained to further calculate the soil water electrical conductivity. According to the process of calculating the soil solution electrical conductivity based on the apparent conductivity of soil, the error of the calculation equation is effectively calculated by the two order curve fitting method. Meanwhile the genetic algorithm is adopted to reduce the influence of the data error generated by the proposed algorithm, and improve the accuracy of the data as well. The experimental results demonstrate that the solution by the proposed algorithm can be effectively obtained and the error change is in one direction simultaneously. With these advantages, we can use soil water electrical conductivity to calculate the content of soil salt.

Modeling the effects of different irrigation water salinity on soil water movement, uptake and multicomponent solute transport

Summary Simulation models can be important tools for analyzing and managing irrigation, soil salinization or crop production problems. In this study a mathematical model that describes the water movement and mass transport of individual ions (Ca 2+ , Mg 2+ and Na + ) and overall soil salinity by means of the soil solution electrical conductivity, is used. The mass transport equations of Ca 2+ , Mg 2+ and Na + have been incorporated as part of the integrated model WANISIM and the soil salinity was computed as the sum of individual ions. The model was calibrated and validated against field data, collected during a three year experiment in plots of maize, irrigated with three different irrigation water qualities, at Thessaloniki area in Northern Greece. The model was also used to evaluate salinization and sodification hazards by the use of irrigation water with increasing electrical conductivity of 0.8, 3.2 and 6.4 dS m −1 , while maintaining a ratio of Ca 2+ :Mg 2+ :Na + equal to 3:3:2. The qualitative and quantitative procedures for results evaluation showed that there was good agreement between the simulated and measured values of the water content, overall salinity and the concentration of individual soluble cations, at two soil layers (0–35 and 35–75 cm). Nutrient uptake was also taken into account. Locally available irrigation water ( EC iw = 0.8 dS m −1 ) did not cause soil salinization or sodification. On the other hand, irrigation water with EC iw equal to 3.2 and 6.4 dS m −1 caused severe soil salinization, but not sodification. The rainfall water during the winter seasons was not sufficient to leach salts below the soil profile of 110 cm. The modified version of model WANISIM is able to predict the effects of irrigation with saline waters on soil and plant growth and it is suitable for irrigation management in areas with scarce and low quality water resources.