Saturated Soil Paste Extract Research Articles

Soluble ions dynamics in Mediterranean coastal pinewood forest soils interested by saline groundwater

The aim of the study was to evaluate the dynamics of soluble ions in the soils of a pinewood forest of the Mediterranean coastal area in the Province of Ravenna, Italy. A one year monitoring was carried out in four Entisols of the San Vitale pinewood forest, a vulnerable natural area due to subsidence and salt water intrusion. Ionic soluble forms were examined in saturated paste extracts (SPEs) and compared to groundwater soluble forms. Due to the local thermo-pluviometric conditions, both the water table depth and groundwater electrical conductivity (ECw) varied widely ranging respectively from 0 to −162cm in depth and from 2 to 28dS·m−1 in salinity content. As expected, this greatly influenced soluble ions concentrations in soil horizons, leading to variations in salt's speciation.In soils with a deep water table (Typic Ustipsamments), superficial horizons showed a prevalence of Ca2+ and HCO3– ion forms during the whole year, while in the deep horizons, Na+ and Cl− were the dominant ions. During summertime in soils with a shallow water table (Sodic Psammaquents), superficial ions enrichment was detected with Na+ and Cl− ions being prevalent. Autumn and winter rainfall provoked the leaching of both Na+ and especially of Cl− ions, leaving HCO3– as the main anion. In the soils with intermediate water table depth and moderate salinity (Aquic Ustipsamments), less relevant variations were observed. During winter the Ca2+ ion was the most present at the soil surface together with HCO3−. During summer Ca2+ and Cl− were the most present ions at the soil surface. At deeper horizons Na+ and Cl− ions always prevailed. The sodium adsorption ratio (SAR) reached the greatest values (>40) during summertime in Sodic Psammaquents superficial horizons and in Typic Ustipsamments deep horizons. On the basis of mixing curves, Na+ and Cl− displayed a conservative behavior and a likely sea origin. Both the Ca2+ and SO42− ions appeared to be partially released from the solid soil fraction, while the Mg2+ ion seemed to be partially absorbed by the solid matrix. On the basis of the hydrochemical characterization of both groundwater and soil SPEs, it was possible to identify different refreshing and salinization processes along the soil profiles. The one year monitoring of both the whole soil profile and groundwater, never performed before, allows a better understanding of the presence of distinct plant species and disease symptoms.

Response of Spring Wheat to Sulfate‐Based Salinity Stress under Greenhouse and Field Conditions

Core Ideas Spring wheat response to sulfate‐based salinity stress was evaluated under greenhouse and field conditions. Soil salinity was highly variable, both horizontally and vertically, in fields. Soil ECe affected crop growth and relative yield only under greenhouse conditions. Under field conditions, low soil ECe in the root zone resulted in greater salinity tolerance. Spring wheat (Triticum aestivum L.), a moderately salt‐tolerant crop, is often grown in saline areas worldwide. This study was conducted to assess spring wheat response to sulfate‐based salts under greenhouse and field conditions. In a greenhouse experiment, salinity treatments (control and 3.0, 5.0, 9.0, and 15.0 dS m−1) were established by adding Na2SO4 and MgSO4⋅7H2O salts in soil–silica mixes. Similarly, field studies were conducted in naturally saline farmers’ fields in eastern North Dakota for a total of four site‐years. In the fields, the soil was sampled to the 120‐cm depth, and the depth‐weighted mean root‐zone salinity was calculated. Results indicated a variable response of spring wheat to salinity under greenhouse and field conditions. Under greenhouse conditions, plant height and number of tillers per plant decreased significantly at a soil saturated paste extract electrical conductivity (ECe) of 5 dS m−1 and above. Similarly, root growth decreased significantly at a ECe of 9.0 dS m−1 and above. Relative kernel and straw yields were unaffected by sulfate salts up to 8.2 and 2.9 dS m−1, respectively. Above the threshold value, the kernel and straw yields declined by 12.0 and 4.9% per unit increase in ECe, respectively. In naturally saline fields, soil salinity decreased with soil depth, and the spring wheat responded by decreasing plant height by 1.2 cm per unit increase in ECe. However, root growth and relative crop yields were maintained. Our results suggest that the majority of the crop roots were exposed to low salinity levels in the surface soil layers in naturally saline fields, providing greater salinity tolerance in the crops.

Enhancing Subsurface Drainage to Control Salinity in Dryland Agriculture

Abstract. Controlling the physical processes of soil salinization involves lowering ground water levels, draining the vadose zones, and leaching excess salts from root zones. Plastic drain tubing strategically placed 1.5 to 1.8 m below the surface in semiarid lands can lower water tables and drain phreatic water, but irrigation is usually required to satisfactorily leach the offending salts. In non-irrigated drylands, the leaching process depends on natural precipitation, but the drier the climate, the greater the need for more leaching water. Possible practices which tap complementary water in conjunction with subsurface drainage include: (1) establishment of roughness barriers to trap wind-borne snow, and (2) pumping water from near-surface, ground water mounds. The mean electrical conductivity of saturated soil paste extracts sampled yearly from a semiarid site in Saskatchewan averaged 14.1 dS m-1 during the six years before the drainage was installed, 13.0 dS m-1 for two years just after drainage but before capturing blowing snow, and 9.6 dS m-1 for the six years following. The average barley grain harvested during the six years prior to drainage yielded 330 kg ha-1 and 2414 kg ha-1 after installation of the enhanced drainage system. In a follow-up sub-study, fall applications of 4.6 dS m-1 mounded ground water from a shallow well fitted with a solar-powered pump within a drainage system preceded spring seeding of alfalfa. Enhanced drainage improved mean seedling emergence from 20% to 79%. Every 28 mm of ground water applied, up to 2273 mm, increased alfalfa emergence by 1%. Keywords: Agricultural drainage, Plant emergence, Pre-seeding irrigation, Solar-powered pumping, Soil reclamation, Soil salinity, Windbreaks.

Estimation of the Electrical Conductivity of Saturated Paste Extract Using a Dielectric Sensor

AbstractThe electrical conductivity of saturated soil-paste extract (ECe) has been extensively used as the standard index for soil salinity assessment. However, this method is time-consuming and la...

Mapping soil salinity and a fresh-water intrusion in three-dimensions using a quasi-3d joint-inversion of DUALEM-421S and EM34 data

In order to understand the drivers of topsoil salinization, the distribution and movement of salt in accordance with groundwater need mapping. In this study, we described a method to map the distribution of soil salinity, as measured by the electrical conductivity of a saturated soil-paste extract (ECe), and in 3-dimensions around a water storage reservoir in an irrigated field near Bourke, New South Wales, Australia. A quasi-3d electromagnetic conductivity image (EMCI) or model of the true electrical conductivity (σ) was developed using 133 apparent electrical conductivity (ECa) measurements collected on a 50m grid and using various coil arrays of DUALEM-421S and EM34 instruments. For the DUALEM-421S we considered ECa in horizontal coplanar (i.e., 1mPcon, 2mPcon and 4mPcon) and vertical coplanar (i.e., 1mHcon, 2mHcon and 4mHcon) arrays. For the EM34, three measurements in the horizontal mode (i.e., EM34-10H, EM34-20H and EM34-40H) were considered. We estimated σ using a quasi-3d joint-inversion algorithm (EM4Soil). The best correlation (R2=0.92) between σ and measured soil ECe was identified when a forward modelling (FS), inversion algorithm (S2) and damping factor (λ=0.2) were used and using both DUALEM-421 and EM34 data; but not including the 4m coil arrays of the DUALEM-421S. A linear regression calibration model was used to predict ECe in 3-dimensions beneath the study field. The predicted ECe was consistent with previous studies and revealed the distribution of ECe and helped to infer a freshwater intrusion from a water storage reservoir at depth and as a function of its proximity to near-surface prior stream channels and buried paleochannels. It was concluded that this method can be applied elsewhere to map the soil salinity and water movement and provide guidance for improved land management.

Characterizing Spatial–Temporal Changes of Soil and Crop Parameters for Precision Management in a Coastal Rainfed Agroecosystem

Understanding the intrinsic relationship between highly varied crop productivity and soil characteristics is essential for developing site‐specific management practices. Our primary objectives were to quantify the temporal variation of soil attributes and crop productivity, to characterize the spatiotemporal variability and to delineate management zones of crop productivity for precision management. A pool of 12 soil properties (0–15 cm) and crop annual output (CAO) were collected annually from corn (Zea mays L.)–barley (Hordeum vulgare L.) rotation for three consecutive years in a coastal rainfed agroecosystem of East China. Results indicated that varying degrees of sustained temporal increase were observed for percentage of clay particles (CL), soil organic carbon (SOC), available nitrogen (AN), and CAO, whereas electrical conductivity of saturated soil paste extract (ECe), sodium adsorption ration (SAR) and soil available potassium (AK) declined continuously. The ECe and SOC had the largest negative and positive contribution to CAO, respectively. An overall increasing trend was observed for CL, SOC, and CAO whereas ρb and ECe decreased over the 3‐yr period. Followed by CAO and SOC, soil ECe had the lowest degree of temporal stability, and ρb and CL had the highest degrees of temporal stability. Separating the experimental site into two management zones effectively discriminated the spatial variability of crop and soil and reduced the necessary sampling volume. It is concluded that the spatial and temporal coherence of soil and crop parameters can be successfully used to develop site‐specific management zones and reduce sampling efforts for precision management.Core Ideas Percentage of clay particles, soil organic carbon, and crop annual output increased while soil bulk density and electrical conductivity of saturated soil paste extract decreased over the 3‐yr period. Electrical conductivity of saturated soil paste extract showed temporal instability, and soil bulk density and percentage of clay particles exhibited temporal stability. Separating the field into two management zones proved to be a good compromise. The two management zones contributed to reducing sampling efforts.

Response of young bearing olive trees to irrigation-induced salinity

Expansion of irrigated olives, combined with prevalence of water containing dissolved salts, leads to irrigation-induced exposure of olive trees to salinity. Root zone salinity can rise either as a function of increasing input irrigation water salinity (ECi) or relative reductions in water for leaching. We investigated five ECi levels from 0.5 to 11.0 dS m−1 with a constant leaching fraction (LF) of 0.29 and five leaching levels from 0.05 to 0.44 (drainage: irrigation ratio) with water of ECi = 5.0 dS m−1 on young bearing Olea europaea cv Barnea olive trees grown in 2.5 m3 weighing-drainage lysimeters over three years. Tree-scale response to increased salinity did not demonstrate any sign of a threshold value and was not differentiated by the cause of salinity, be it changes in input irrigation water salt concentrations or changes in LF. Soil salinity, measured as electrical conductivity of saturated soil paste extract (ECe) and maintained at stable levels over time, decreased tree water consumption and tree size measured as trunk area or above-ground biomass by 40–60 % as it increased from 1.2 to around 3.5–4.0 dS m−1. Further increases in ECe to as high as 7.5 dS m−1 brought these parameters to 20–30 % of the treatment with low salinity. Fruit yield also decreased with increasing salinity, albeit with less drastic relative effects. An analytical model calculating water and salt balance and subsequent evapotranspiration or biomass as a function of irrigation water quantity and salinity successfully predicted the measured results.

Indirect Measurement of Electrical Conductivity and Exchangeable Cations on Soil Water Extracts

The electrical conductivity of saturated soil paste extracts with respect to the electrical conductivity of extracts obtained applying different soil-water dilution ratios (from 1:1 to 1:5) was estimated considering 194 soil samples of different texture, salinity, and pH. A smaller data set composed by 50 samples was used to estimate exchangeable sodium percentage (ESP) values from the concentration of soluble cations determined on 1:2 water extracts. Both estimation procedures were carried out applying a linear multivariate model, according to a “stepwise” approach. The dilution ratio 1:2 provided the best estimates, although all the dilution ratios gave reasonable results. The ESP prediction model included the concentration of soluble sodium; the addition of electrical conductivity and pH values of the 1:2 soil-water extracts improved precision.

Investigation of Soil Physico-chemical Properties in Saemangeum Reclaimed Tidal Land in Korea

This study was conducted to investigate the physical and chemical properties of soils in Saemangeum reclaimed lands. The investigated areas were total 5,020 ha which included 220 ha for Agricultural Life site, 2,450 ha for Tourism & Leisure site, 1,130 ha for Industrial & Research site, 820 ha for Bioenergy crop production site, and 400 ha for Rural City site. Soil samples consisting of the upper 20 cm from the surface were collected in every 200 m × 500 m of the each site in March and September, 2015. Particle size distribution of soils in the reclaimed land was 83.2% sand, 8.6% silt and 8.2% clay in average. Soil texture was distributed as 40.8% sandy soil, 35.5% loamy sand, and 19.7% sandy loam. Based on the investigation of soil chemical properties conducted in March, 2015, soil pH, electrical conductivity of a saturated soil paste extract (ECe), and exchangeable (Exch.) K + and Mg2 + concentrations were higher than those of the optimum levels for upland soil, whereas soil organic matter content, available (Avail.) phosphate concentration, and Exch. Ca 2+ concentration were lower than those of the optimum ranges. Depending on the results of the soil chemical properties measured in September, 2015, soil pH, ECe, and Exch. K + concentration were higher than those of the optimum levels, but soil organic matter, Avail. phosphate, and Exch. Ca 2+ concentration were lower than the optimum ranges. In addition, distribution of sodic soil ranged between 41.4% and 50.0%, and saline soils were from 16.4 to 31.8%. Soils with pH values above 7.0 increased from 15.3% in March to 35.2% in September. Soils with ECe values over 4.8 dS m- 1 increased from 45.6% to 50.7%, whereas soils with the values below 2.0 dS m -1 decreased from 42.8% to 36.9%.

Adjustment of Soil Saturated Paste Extract Electrical Conductivity and Sodium Adsorption Ratio for Excess Gypsum Dissolution Using Equilibrium Geochemical Modeling

Core Ideas In gypsum‐bearing soils, excess dissolution occurs in the soil saturated paste extract. EC and SAR may be adjusted for dissolution effects using geochemical modeling. Characterization of salinity and sodicity hazard is improved. Soil saturated paste extract (SPE) electrical conductivity (ECe) and sodium adsorption ratio (SARe) are widely used measures of soluble salts used to evaluate the salinity hazard to crop growth and the sodicity hazard to soil permeability. In gypsum‐bearing soils, sparingly soluble gypsum dissolves during preparation of the SPE as a result of soil water dilution. This produces a higher measured ECe and lower SARe than would be measured if only field‐soluble gypsum were present. As part of a soil remediation project, samples were collected from the location of a former oil and gas production facility with highly saline‐sodic, brine‐affected soils. The naturally calcareous silt loam soil with a smectitic clay fraction was previously amended with gypsum to mitigate elevated sodicity, of concern for sodic effects on soil permeability. The equilibrium geochemical modeling software program ExtractChem was used to model ECe and SARe in the absence of excess gypsum dissolution by first modeling EC and SAR at field water content and then modeling ECe and SARe at saturated paste water content while excluding gypsum from the modeled reaction. For samples with measured ECe <3 dS m−1, ECe modeled in the absence of excess gypsum dissolution was up to 52% lower than measured, and for samples with measured SARe <2, modeled SARe was up to 53% higher than measured. As remediation progressed, and ECe and SARe decreased toward target values, the magnitude of the excess gypsum effect was sufficient to affect the evaluation of remedial progress. Equilibrium geochemical modeling adjustment of ECe and SARe for gypsum dissolution that occurs as a result of SPE preparation is recommended to improve the evaluation of the progress of remediation of gypsum‐bearing, salt‐affected soil.

Irrigation salinity hazard assessment and risk mapping in the lower Macintyre Valley, Australia

In the Murray–Darling Basin of Australia, secondary soil salinization occurs due to excessive deep drainage and the presence of shallow saline water tables. In order to understand the cause and best management, soil and vadose zone information is necessary. This type of information has been generated in the Toobeah district but owing to the state border an inconsistent methodology was used. This has led to much confusion from stakeholders who are unable to understand the ambiguity of the results in terms of final overall risk of salinization. In this research, a digital soil mapping method that employs various ancillary data is presented. Firstly, an electromagnetic induction survey using a Geonics EM34 and EM38 was used to characterise soil and vadose zone stratigraphy. From the apparent electrical conductivity (ECa) collected, soil sampling locations were selected and with laboratory analysis carried out to determine average (2–12m) clay and EC of a saturated soil-paste extract (ECe). EM34 ECa, land surface parameters derived from a digital elevation model and measured soil data were used to establish multiple linear regression models, which allowed for mapping of various hazard factors, including clay and ECe. EM38 ECa data were calibrated to deep drainage obtained from Salt and Leaching Fraction (SaLF) modelling of soil data. Expert knowledge and indicator kriging were used to determine critical values where the salinity hazard factors were likely to contribute to a shallow saline water table (i.e., clay ≤35%; ECe>2.5dS/m, and deep drainage >100mm/year). This information was combined to produce an overall salinity risk map for the Toobeah district using indicator kriging. The risk map shows potential salinization areas and where detailed information is required and where targeted research can be conducted to monitor soil conditions and water table heights and determine best management strategies.

Effects of Irrigation Volume and Saline Water On Maize Yield and Soil in Southern Italy

AbstractA field experiment was carried out in southern Italy to investigate the effects of irrigation and salinity on a maize crop and soil properties. The experiment was laid out comparing different irrigation rates (I1, I2, I3—re‐establishing 50, 75 and 100% of the calculated maximum evapotranspiration) and water quality (FW, fresh water and SW, saline water).Grain yield was significantly greater by 60% in 2008 than in 2010. No significant difference was shown for grain yield between the irrigation treatments, whereas water productivity decreased significantly with increasing irrigation rates. Irrigation with saline water did not significantly reduce grain yield compared with fresh water, but it improved grain quality with higher protein content (9.1%) and lower grain moisture percentage (13.3%).Saline water determined a significant increase of saturated soil paste extract Na, ECe, SAR, some exchangeable cations and ESP compared with FW in both years. Furthermore, at the end of the experiment these parameters were lower than those at the end of the first maize crop. Lastly, in the saline treatment, at the end of the trial, the ECe and ESP values were below the critical threshold for soil salinization and/or sodification. Copyright © 2016 John Wiley & Sons, Ltd.

Mapping Salinity in Three Dimensions using a DUALEM-421 and Electromagnetic Inversion Software

To implement management plans, the salt content across affected fields and with depth needs mapping. In this study, we developed a method to map the distribution of normal, uniformly saline, and inverted salinity profiles. We did this by establishing a linear regression (LR) between calculated true electrical conductivity (σ) and electrical conductivity of the saturated soil-paste extract (ECe). We estimated σ by inverting the apparent electrical conductivity (ECa) collected from a DUALEM-421. The ECa values were collected along 13 parallel transects spaced 50 m apart. The inversion was performed using a quasi-three-dimensional model available in the EM4Soil software, where we chose the full solution and S1 inversion algorithm with a damping factor (λ) of 0.3. Using cross-validation, the quasi-three-dimensional model yielded a high accuracy (RMSE = 5.28 dS m−1), small bias (mean error [ME] = −0.03 dS m−1), and large R2 (0.88) and Lin's concordance (0.93). While slightly better results were achieved using individual LRs established at each depth increment overall (i.e., RMSE = 4.35 dS m−1, ME = −0.17 dS m−1, R2 = 0.92, and Lin's concordance = 0.96) and with the DUALEM-421 ECa, the inversion approach requires the development of a single LR (i.e., ECe = 4.1253 + 0.0167σ), which enables efficiencies in estimating salinity and allows ECe to be estimated at any depth where σ was estimated within a three-dimensional electromagnetic conductivity image. This can improve understanding of the cause and best management of salinity. Improvements in accuracy and bias can be achieved by collection of ECa on more closely spaced transects.

An Error Budget for Mapping Field-Scale Soil Salinity at Various Depths using Different Sources of Ancillary Data

To manage soil salinity, farmers need to map its variation, often quantified as the electrical conductivity of a saturated soil-paste extract (ECe, dS m-1). However, ECe determination is time-consuming and expensive. Previous studies have evaluated the use of digital elevation models (DEMs, i.e., elevation), airborne γ-ray (γ-ray) spectrometry (i.e., K, U, and Th) and electromagnetic (EM, i.e., EM38 and EM34) data to map ECe at the district scale. Herein we use similar ancillary data set and empirical best linear unbiased prediction (E-BLUP) to make maps of ECe at different depth intervals (0–0.25, 0.25–0.50, and 0.50–0.75 m) at the field scale. The ancillary data was collected using a ground-based mobile sensing system which included; a GPS which provided spatial coordinates (Easting, Northing), a RS700 (γ-ray) mobile spectrometer, and a DUALEM-1. An error budget procedure was conducted to quantify the model, input, and individual covariate errors of ECe. Results show that while none of the γ-ray data were significant, scaled Easting, elevation, and 1-m horizontal coplanar (1mHcon) were optimal for mapping ECe at 0 to 0.25 m, while 1mHcon was optimal at 0.25 to 0.50 m and 0.50 to 0.75 m. Among all the individual covariate errors for mapping 0- to 0.25-m ECe, elevation (0.40 dS m-1) was smallest, followed by 1mHcon (2.23 dS m-1). To reduce error, additional soil samples are necessary to prevent the edge effect of the kriging process. Additionally, inversion of EM data could be used to improve ECe mapping considering the relatively large model error associated with EM data in the subsoil of inverted salinity profiles.

Effects of saline irrigation on yield and qualitative characterization of seed of an amaranth accession grown under Mediterranean conditions

SUMMARYYield responses of a grain amaranth accession to different irrigation strategies were evaluated in Naples, Italy. Field experiments were carried out to evaluate the quantitative and qualitative response of amaranth under combined abiotic stresses (salinity and drought) in a Mediterranean environment of South Italy affected by problems due to groundwater salinization from seawater intrusion.A comparison was made in 2009 and 2010 between a fully irrigated treatment (1·00), with the restitution of all of the water necessary to replenish to field capacity the soil layer explored by roots (0·00–0·36 m), and two treatments with restitution of 0·50 and 0·25 of the water volume used for the fully irrigated treatment. The three levels of irrigation volume were combined with two levels of salinity, either fresh or salt water, with electrical conductivity (EC) of the irrigation water of 0·64 and 22 dS/m respectively, in a factorial experiment thus harbouring six treatments in a randomized complete block design. The results showed good adaptation of amaranth to drought. It was possible to obtain high yields even if groundwater with infiltrated seawater was used for irrigation (50% yield reduction when the EC of soil saturated paste extract (ECe) was 13·97 dS/m). A reduction of 50% in the volume of irrigation did not cause a significant reduction in yield, whether using fresh or saline water, compared to the treatment fully irrigated with fresh water. The chemical composition of amaranth seeds, however, was significantly affected by the treatments. Starch and ash content decreased with increasing drought while protein content was increased by both salt and drought.In view of the increased presence of salinity and drought stress in the Mediterranean area and the scarce information on amaranth response to salt and water stress, the aim of the present work is evaluation of the quantitative and qualitative response of amaranth grown in a Mediterranean environment of South Italy under combined drought and salinity stress.

Modeling Soil Salinity along a Hillslope in Iran by Inversion of EM38 Data

Electromagnetic (EM) induction has been used to characterize the spatial distribution of salinity. However, most studies have been undertaken to map the areal distribution of the average profile salinity using measurements of the apparent electrical conductivity (ECa, mS m−1). In this study, an EM38 was used to map the distribution of salinity with depth along a 26-km hillslope in central Iran. We generated electromagnetic conductivity images by inverting EM38 ECa data collected at various heights in the EM4Soil software. A number of parameters including forward modeling (cumulative function, CF, and full solution, FS), inversion algorithms (S1 and S2), damping factor (λ), and combinations of different heights were considered to generate calculated soil true electrical conductivity (σ, mS m−1). By comparing different σ against the electrical conductivity of a saturated soil-paste extract (ECe, dS m−1) at various depths, we found that the strongest correlation and smallest modeling error was achieved using the FS, S1, λ = 12, and ECa data collected at 0.4 m alone. We then compared the results achieved by developing a linear regression between σ and ECe at various depths with those achieved using multiple linear regression (MLR) established between ECa and ECe. The inversion method was less time consuming and more robust than the MLR approach. The predicted ECe increased from the crest to the base of the toposequence. The results were consistent with the underlying geology, climate, and local topography. The methodology can be used as guidance for baseline salinity monitoring and management.

Estimation of soil salinity in a drip irrigation system by using joint inversion of multicoil electromagnetic induction measurements

AbstractLow frequency electromagnetic induction (EMI) is becoming a useful tool for soil characterization due to its fast measurement capability and sensitivity to soil moisture and salinity. In this research, a new EMI system (the CMD mini‐Explorer) is used for subsurface characterization of soil salinity in a drip irrigation system via a joint inversion approach of multiconfiguration EMI measurements. EMI measurements were conducted across a farm where Acacia trees are irrigated with brackish water. In situ measurements of vertical bulk electrical conductivity (σb) were recorded in different pits along one of the transects to calibrate the EMI measurements and to compare with the modeled electrical conductivity (σ) obtained by the joint inversion of multiconfiguration EMI measurements. Estimates of σ were then converted into the universal standard of soil salinity measurement (i.e., electrical conductivity of a saturated soil paste extract – ECe). Soil apparent electrical conductivity (ECa) was repeatedly measured with the CMD mini‐Explorer to investigate the temperature stability of the new system at a fixed location, where the ambient air temperature increased from 26°C to 46°C. Results indicate that the new EMI system is very stable in high temperature environments, especially above 40°C, where most other approaches give unstable measurements. In addition, the distribution pattern of soil salinity is well estimated quantitatively by the joint inversion of multicomponent EMI measurements. The approach of joint inversion of EMI measurements allows for the quantitative mapping of the soil salinity distribution pattern and can be utilized for the management of soil salinity.

Green Long Pepper Growth under Different Saline and Water Regime Conditions and Usability of Water Consumption in Plant Salt Tolerance

Both electrical conductivity of soil saturation paste extract (ECe) and plant water consumption (ET) should be considered for assessing crop yield tolerances to salinity since ET decreases by increased salinity effects. In this study, conducted in a greenhouse under controlled conditions, it was afforded to use soil salinity and water consumption for the purpose of assessing plant responses to salinity. Additionally, growth and yield of green long pepper (Capsicum annuum L. Demre) under different saline and water regime conditions were examined. For these purposes, the green long pepper were exposed to six water salinity levels (S1= 0.65; S2= 2.0; S3= 3.0; S4= 4.0; S5= 5.0 and S6= 7.0 dS m-1) and four water application rates (IR1= 1.43; IR2= 1.0; IR3= 0.75 and IR4= 0.50 times of depleted water). The yield response factor (Ky), is 1.56 for salinity stress and 1.66 for water stress. Water consumption of the plant exponentially decreased (ET= 0.83×ECe-0.17) whereas relative fruit yield decreased linearly (7.03%) for unit increase in soil salinity after a threshold value of 1.20 dS m-1. A stronger three-dimensional relation was found among relative yield, relative water consumption and soil salinity (R2= 0.94). Using water consumption as a second factor in evaluation of plant response to salinity may be useful for reflecting effects of different climatic conditions

A one-year post-fire record of macronutrient cycling in a mountain sandstone fynbos ecosystem, South Africa

Nutrient inputs and dynamics of the fynbos ecosystem, particularly after a fire, are poorly understood. This article provides chemical analyses of macronutrients (Cl, Na, SO4, Mg, Ca and K) in rainwater, stream water, soil and bedrock over a period of one year following a fire event in a coastal mountain sandstone fynbos ecosystem.Rainwater, stream water, soil and bedrock samples were taken from a mountain fynbos area underlain by homogeneous Peninsula Formation sandstone bedrock for a one-year period. Rainwater, stream water and soil saturated paste extracts were analysed for macronutrients using a Dionex DX-120 Ion Chromatograph. Crushed soil and bedrock samples were analysed for major element oxide and S content.Above-ground biomass recovery after one year was modest (5–10% of the 19-year-old pre-fire biomass) with marine aerosols supplying Cl and Na ions to the ecosystem and a significant amount of Mg, SO4, Ca and K. Additional Mg, SO4, Ca and K are supplied by deposition of local and regional fire ash and dust (mineral aerosols) transported from inland sources mostly by northwesterly winter winds. Nutrient loss diminishes rapidly with the return of pre-fire stream values within 9months after fire, with nutrients gradually replaced through atmospheric deposition rather than the slow weathering bedrock.Macronutrients supplied to the study area reflect seasonal differences with atmospheric processes being the primary source of nutrients to the ecosystem.

An error budget for soil salinity mapping using different ancillary data

Secondary soil salinisation occurs as a function of human interaction with the landscape. Increasing salinity is a major constraint to crop yield. The electrical conductivity of a saturated soil-paste extract (ECe, dS m–1) defines the level of salinity in soil. In order to manage salinity, farmers need to map its variation. However, ECe determination is time-consuming and expensive. Digital mapping of ECe is possible by using ancillary data such as easy-to-obtain digital elevation model, gamma-ray spectrometry and electromagnetic (EM) induction data. In this paper, we used these ancillary data and empirical best linear unbiased prediction (E-BLUP) to make a digital map of ECe. In this regard, we found that elevation, radioelement of thorium (Th) and logEM38-v were the most statistically useful ancillary data. We also developed an error-budget procedure to quantify the relative contributions that model, input (for all the ancillary datasets), and combined and individual covariate (for each of the ancillary datasets) error made to the prediction error of our map of ECe. The error-budget procedure used ordinary kriging, E-BLUP and conditional simulation to produce numerous realisations of the data and their underlying errors. Results show that the combined error of model error and input error was ~4.44 dS m–1. Compared with the standard deviation of observed soil ECe (3.61 dS m–1), the error was large. Of this error, most was attributable to the input error (1.38 dS m–1), which is larger than the model error (0.02 dS m–1). In terms of the input error, we determined that the larger standard deviation is attributable to the lack of ancillary data, namely the ECa in areas adjacent to the Darling River and on the aeolian dune where data collection was difficult owing to dense native vegetation.