Saturated Paste Extract Research Articles

Response of Daylily (Hemerocallis hybridus cv. ‘Stella de oro’) to saline water irrigation in two coastal saline soils

In order to evaluate the effects of irrigation water salinity, applied by drip irrigation, on Daylily (Hemerocallis hybridus cv. ‘Stella de oro’) growth and soil salinity, a three-year experiment was conducted in coastal saline region in Caofeidian District East China during 2013–2015 in two soils (sandy loam and silt). Five water salinity treatments were used with saline water at electrical conductivity (ECiw) of 0.8, 3.1, 4.7, 6.3, and 7.8 dS/m. The original soil salinity expressed as electrical conductivity of the saturation paste extract (ECe) was 27–30dS/m in the 0–95cm depth. Results showed that drip-irrigation was effective in salt leaching. The average values of soil ECe for five treatments were 1–4 and 2–6 dS/m in 0–35cm soil profiles of sandy loam and silt soils, respectively, after 18 months with drip irrigation. In 2014–2015, the survival rates were all >93% when irrigated with saline water at <7.8dS/m for both saline soils. The survival rate and dry mass decreased by 0.63% and 17.14% for each unit of EC increase in the irrigation water in sandy loam saline soil, and the corresponding values were 0.70% and 25.63% in silt saline soil. This study implied that Daylily is a suitable plant in landscape construction of coastal saline soils using drip-irrigation at ECiw<7.8dS/m.

Comparison of soil-to-water suspension ratios for determining electrical conductivity of oil-production-water-contaminated soils

Soil salinity caused by oil-production-water (brine) contamination is a major issue in regions of oil and gas development. However, rapid site assessment tools such as soil-to-water suspension electrical conductivity (EC) methods and conversion equations have not been previously calibrated and validated for brine-contaminated soils. Our objective was to compare three soil EC methods and derive conversion equations for EC values commonly observed at brine-spill sites. Brine-contaminated soils from western North Dakota were assessed for salinity. Electrical conductivity was determined using 1:1 and 1:5 soil-to-water suspensions (EC1:1, EC1:5) and saturated paste extracts (ECe). Soil EC equilibration times for soil-to-water suspensions were also assessed. Significant relationships (r2 = 0.91 to 0.97, P &lt; 0.0001) existed among all methods for EC values ranging between 0 and 126 dS m−1. Conversion equations were developed based on these relationships and then validated with an independent data set. These new equations reduced ECe prediction errors by 2 to 4.5 times when compare with 14 predictive equations reported in the literature. The conversion equations developed here are recommended for use in remediation efforts when converting EC1:1 and EC1:5 data to ECe on brine-contaminated and noncontaminated soils where ECe is highly correlated to Na concentrations.

Response of Symphyotrichum novi-belgii and Dianthus chinensis L. to saline water irrigation in a coastal saline soil

Symphyotrichum novi-belgii and Dianthus chinensis L. perform well in landscape. However, their tolerance to salinity stress is unknown. Field experiment was conducted to evaluate the salt tolerance threshold (STI) of these two herbaceous plants cultivated in a coastal saline soil by drip-irrigation with saline water at electrical conductivity (EC) of 0.8, 3.1, 4.7, 6.3, and 7.8dS/m for three years. The original soil salinity expressed as electrical conductivity of the saturation paste extract (ECe) was an average of 27.64dS/m in the 0–95cm depth. Our results showed that drip-irrigation was effective in salt leaching. After 18 months, the average values of soil ECe for five treatments were 2.32 and 2.78dS/m in 0–35 and 0–95cm soil profile, respectively. The survival rates were >94% and >80% when irrigated with saline water at <7.8dS/m for S. novi-belgii and D. chinensis L., respectively. The survival rate and shoot dry mass decreased by 0.76% and 9.24% for each unit of EC increase in the irrigation water for S. novi-belgii, and the corresponding values were 3.01% and 8.21% for D. chinensis L. This study implied that S. novi-belgii and D. chinensis L. are suitable plants in landscape construction of coastal saline soils using drip-irrigation with suitable saline water range.

Nutrient status and irrigation management affect anthocyanins in ‘Mollar de Elche’ pomegranate

Pomegranate (Punica granatum L.) is a deciduous fruit tree native of central Asia included in the so-called group of minor fruit tree species. Although not widely grown, it has some importance in the east and southeast of Spain, where there are about 3100 ha of commercially cultivated pomegranates. In semi-arid climate areas like Spain, irrigation management is a powerful tool to influence tree water status agronomic performance and fruit composition. The present research focused on determining the effects of soil fertility level, plant nutrient status and irrigation strategies on fruit quality attributes of 'Mollar de Elche' pomegranates. The experiment monitored the concentrations of 12 nutrients in leaf samples from 15 commercial orchards. Soil fertility levels in air-dried soil samples were analyzed for texture, pH (1:2.5 water extract), electrical conductivity (saturated paste extract), organic matter, nitrogen, total and active lime, extractable phosphorous (P) (Olsen), and available cations (extractable with ammonium acetate). In addition, an experimental orchard with various deficit irrigation strategies was established. No linear correlations were found between fruit color and soil and foliar nutrient composition for pomegranates grown in the soils of this area, with high levels of Ca and Na exchangeable cations. Deficit irrigation, when applied in the summer during the main linear fruit growth period, significantly increased the total anthocyanin concentration.

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.

Two fixed ratio dilutions for soil salinity monitoring in hypersaline wetlands.

Highly soluble salts are undesirable in agriculture because they reduce yields or the quality of most cash crops and can leak to surface or sub-surface waters. In some cases salinity can be associated with unique history, rarity, or special habitats protected by environmental laws. Yet in considering the measurement of soil salinity for long-term monitoring purposes, adequate methods are required. Both saturated paste extracts, intended for agriculture, and direct surface and/or porewater salinity measurement, used in inundated wetlands, are unsuited for hypersaline wetlands that often are only occasionally inundated. For these cases, we propose the use of 1:5 soil/water (weight/weight) extracts as the standard for expressing the electrical conductivity (EC) of such soils and for further salt determinations. We also propose checking for ion-pairing with a 1:10 or more diluted extract in hypersaline soils. As an illustration, we apply the two-dilutions approach to a set of 359 soil samples from saline wetlands ranging in ECe from 2.3 dS m-1 to 183.0 dS m-1. This easy procedure will be useful in survey campaigns and in the monitoring of soil salt content.

Chinese rose (Rosa chinensis) cultivation in Bohai Bay, China, using an improved drip irrigation method to reclaim heavy coastal saline soils

This study investigated whether an improved drip irrigation method for reclaiming heavy coastal saline silt-soils could improve the growth of salt-sensitive plants threatened by soils with high salt contents and poor soil structures in Bohai Bay, China. Chinese rose (Rosa chinensis), an ornamental salt-sensitive plant, was chosen as the experiment material. The improved method used a non-saline root environment during the early stages of salt-leaching, a gravel–sand layer settled below the saline soil but above the water table and optimal soil moisture conditions. To determine the optimal soil moisture conditions, five soil matric potentials (SMPs) at 20cm depth at −5, −10, −15, −20 and −25kPa were studied. The results indicated that the mean soil electrical conductivity of the saturated paste extracts (ECe) and the sodium adsorption ratio (SAR) significantly declined in all five treatments. After three growing seasons, the highest desalinization ratios and SAR reductions reached 89% and 73%, respectively, compared with their initial values and these occurred in the roots of the seedlings exposed to the −5kPa treatment. The mean ECe and SAR values increased linearly as the SMP declined. The plant survival ratio was not affected by the SMP treatment in the first growing season, due to the non-saline root zone, but decreased significantly as the SMP threshold fell in the spring of the second year, and then remained stable in the following season. The highest survival ratio reached 97% for the −5kPa SMP treatment after three growing seasons. Stem diameter and plant height increased during three growing seasons and the largest increases occurred when the SMP was −5kPa in first year, −10kPa in second year and −20kPa in third year. The largest crown diameters were recorded in the −5kPa treatment plots in second year and −20kPa in third year. After three years of reclamation, our results showed that this improved method, which utilized a non-saline root environment during the early stages of salt-leaching, a gravel–sand layer below the saline soil and controlled the SMP threshold of −5kPa in the first year, −10kPa in second year and −20kPa in third year, can be used to reclaim coastal urban saline land for vegetation rehabilitation around Bohai Bay, China.

Micropattern of halophytic vegetation on technogenic soils affected by the soda industry

The properties of technogenic soils affected by the soda industry are significantly different from natural saline soils occurring in Poland. The long-term impact of post-production waste contributed to the formation of extremely saline soils rich both in sodium chloride (NaCl) and calcium chloride (CaCl2). Despite the strong degradation, these soils play a very important role in the urban ecosystem, because they can provide a habitat for very unique halophytic species. Therefore, in this study, we examined how environmental factors control the micropattern of halophytic vegetation in analyzed industrial soils in Poland. It was hypothesized that species distribution and vegetation variation can be affected by different environmental factors at the local scale. The current study was carried out on three test plots of different microelevation and vegetation cover. In general, Salicornia europaea L. was the most dominant species on each plot, but besides patches dominated only by this species, the other major and distinguished constituents were Puccinelia distans, (JACQ.) PARL. Aster tripolium L. and Triglochin maritima L. Finally, the general vegetation–environmental statistical model (direct ordination–redundancy analysis) was created. The results demonstrated that very diverse microtopography and soil conditions within very small areas were ecologically important. The driving factors for species distribution on each plot were slightly different because of the local differences in environmental conditions. The generalization of vegetation–environment relations performed for all plots together demonstrated that significant, and the most important, factors for plant species distribution in the investigated area were elevation and parameters determined in the saturation paste extracts such as reaction (pHe), chloride content (Cl-) and saturation percentage (SP). As a general rule, species preferred elevated parts of the lower salinity (ECe) and the lower concentration of chloride (Cl–) ions. S. europaea was present at relatively higher salinity compared to A. tripolium, T. maritima and P. distans. Moreover, the presence of P. distans was related to the relatively higher soil pH. The obtained results in the association context present the factors responsible for species variation within the Salicornia europaea plant community, which can be particularly important for restoration of its natural stands.

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

Effect of drip-irrigation with saline water on Chinese rose (Rosa chinensis) during reclamation of very heavy coastal saline soil in a field trial

Drip-irrigation with saline water was used for reclamation of very heavy coastal saline soils and its effects on salt-sensitive plants were also evaluated in a three-year trial in the coastal region of east China. The original soil salinity expressed as electrical conductivity of the saturation paste extract (ECe) was an average of 27.13dS/m in the 0–100cm depth. The experiment included five treatments of salinity levels of 0.8, 3.1, 4.7, 6.3 and 7.8dS/m of irrigation water. Chinese rose (Rosa chinensis), a salt-sensitive species, were planted in the sandy loam soil to determine the effect of saline environment on growth characters and dry matter production. Drip-irrigation had a significant positive impact on salt leaching, and the very highly saline soil became mildly saline after reclamation in root zone of soil profiles irrigated with water of salinity up to 7.8dS/m. An increase in salinity of irrigation water had adverse effects on plant height, stem diameter, survival rate and dry matter production. Root:shoot ratio increased with increasing water salinity. The values of soil-salt tolerance threshold were 2.39dS/m at emergence and 2.78dS/m in the growth period after emergence. The emergence rate and dry mass decreased by 27.39 and 41.19% for each unit of ECe increase in the root zone, respectively. These results implied that drip-irrigation with saline water by controlling soil matric potential under a gravel–sand layer was effective in reclamation of this very heavy coastal saline soil for sensitive species such as Chinese rose.

Responses of Soil Microbial Activity and Biomass to Salinity After Repeated Additions of Plant Residues

Microbial adaptation to salinity can be achieved through synthesis of organic osmolytes, which requires high amounts of energy; however, a single addition of plant residues can only temporarily improve energy supply to soil microbes. Therefore, a laboratory incubation experiment was conducted to evaluate the responses of soil microbes to increasing salinity with repeated additions of plant residues using a loamy sand soil with an electrical conductivity in saturated paste extract (ECe) of 0.6 dS m−1. The soil was kept non-saline or salinized by adding different amounts of NaCl to achieve ECe of 12.5, 25.0 and 50.0 dS m−1. The non-saline soil and the saline soils were amended with finely ground pea residues at two rates equivalent to 3.9 and 7.8 g C kg−1 soil on days 0, 15 and 29. The soils receiving no residues were included as a control. Cumulative respiration per g C added over 2 weeks after each residue addition was always greater at 3.9 than 7.8 g C kg−1 soil and higher in the non-saline soil than in the saline soils. In the saline soils, the cumulative respiration per g C added was higher after the second and third additions than after the first addition except with 3.9 g C kg−1 at ECe of 50 dS m−1. Though with the same amount of C added (7.8 g C kg−1), salinity reduced soil respiration to a lesser extent when 3.9 g C kg−1 was added twice compared to a single addition of 7.8 g C kg−1. After the third residue addition, the microbial biomass C concentration was significantly lower in the soils with ECe of 25 and 50 dS m−1 than in the non-saline soil at 3.9 g C kg−1, but only in the soil with ECe of 50 dS m−1 at 7.8 g C kg−1. We concluded that repeated residue additions increased the adaptation of soil microbial community to salinity, which was likely due to high C availability providing microbes with the energy needed for synthesis of organic osmolytes.

Relationship between 1:5 Soil/Water and Saturated Paste Extract Sodium Adsorption Ratios by Three Extraction Methods

Cations extracted from soil using non-standard techniques are used to calculate the sodium adsorption ratio (SAR). To interpret these values, analytical approaches for converting alternative approaches to standard approaches are needed. The objective of this research was to develop the relationship between the standard approach (saturated paste extract, SARe) and alternative approaches where the cations are in 1: 5 soil/water ratios and are mixed by shaking, stirring, or an NRCS method (allowed to reach equilibrium). One hundred soils sampled from glacial parent materials in North Dakota were selected for this study. The SAR values from the three methods were highly correlated to each other. Simple linear regression (Model 1), robust regression, and Model 2 were analyzed for the relationship between SAR1:5 and SARe. Outlier analysis and calcite content distribution indicated the possible influence of calcite content. The soil data were classified into high and low calcite by a 4.2% criterion. In addition, Ca in the 1:5 and saturated paste extracts showed poor relationships, also indicating that Ca had an influence. Model 1 and robust regression were similar in expressing the relationship between soil SAR1:5 and SARe with a normal residual distribution, but Model 2 had high left skewness in the residual distribution. The model prediction was increased when soil data were classified by calcite content. Predicting the SARe of soils from SAR1:5 data is possible but soil-calcite concentrations should be considered; 1:5 methods can confidently be compared.

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.

Bulk electrical conductivity as an indicator of spatial distribution of nitrogen and phosphorous at feedlots

The increasing demands of producing beef for domestic and international consumption is leading to the development of feedlots in Argentina. Unfortunately, the great amount of manure produces leachate of nitrates and other ions which may affect groundwater quality. The objective of this paper was to identify the spatial distribution of bulk electrical conductivity (ECb) of non-saturated zone and its association with variability of nitrates and bioavailable phosphorous, water content, topography and electrical conductivity of saturated paste extract (EC).The analysis of the impact was done at two pens with different time of confinement of the animals (Pen1 and Pen 2, with 16months and 7years of animal occupation, respectively). The initial exploration phase was done by electrical resistivity tomography (ERT) and electromagnetic induction (EMI) surveys were subsequently performed at a subarea for studying the spatial distribution of ECb. A grid of soil sampling up to 1m depth was done at the same subarea of the EMI survey. A geostatistical interpolation of data was performed in order to map ECb, water content, nitrogen, bioavailable phosphorous and EC.Anomalies of higher conductivity (between 6 and 10 times the background values) were found near the feedbunk and the water trough, being greater on soils with larger period of manure recharge. Water content, nitrogen of nitrates (N-NO3−), bioavailable phosphorous (Pavail.) and EC showed patterns of spatial distribution similar to ECb. These patterns are mainly associated with the runoff movement of water to the lower zones in the case of a steeper slope and the soil compaction as in the Pen 1. In the Pen 2, the patterns of spatial variability are similar for ECb and water content while anomalies of high ECb were found along an abandoned feedbunk. High values of N-NO3−, Pavail. and EC were found at this site. A longer period of manure recharge resulted in higher values of nitrogen and bioavailable phosphorous in soils.It may be stated that bulk electrical conductivity was a good spatial indicator of water, nitrogen and bioavailable phosphorous in sandy loamy soils in these pens for the investigation depth of 1m. The bulk conductivity seems to be primarily associated with water content which is the path of transport of ions through the porous medium. In all the cases, the major contents of nitrogen and bioavailable phosphorous in the soil were associated with high bulk electrical conductivity when water content was above an equivalent depth of water of 100mm. The soil moisture status should be taken into account before an electromagnetic exploration for detecting soil contamination. Regarding the impact on groundwater pollution, the proximity of the water table to the surface seems to be more influential than the animal stocking rate for a longer period.

Boron adsorption–desorption characteristics of irrigated soils in the Jordan Valley

Increasing replacement of fresh water by saline or reclaimed wastewater in the predominantly drip-irrigated Jordan Valley (JV) soils poses a threat of boron (B) accumulation in these soils. Twenty nine composite soil samples in each of the two layers, surface (0–25cm) and subsurface (25–50cm), were collected from sites located along the entire JV. The samples were analyzed for major chemical and physical properties. Water soluble B was determined in both hot water and saturated paste extracts. Boron adsorption was carried out from 50molc/m3 NaCl/CaCl2 background electrolyte solutions of SAR 5, but of increasing B concentration (0.25–4.00μg/mL). These solutions were arranged to percolate duplicate columns of three soil samples representing Northern JV of Shuna (Fluventic Haplustolls), Middle JV of Deir-Alla (Fluventic Haplustepts) and Southern JV of Sweimeh (Typic Torrifluvents). Regeneration of B from soil columns was determined. First, duplicate soil columns were permeated with solutions of constant B concentration of 1.0, 1.5, 2.0 or 4.0μg/mL. Following soil–liquid B equilibrium, the columns were incubated at room temperature for one week then permeated with the background solution of 0μg B/mL. The permeation continued until three successive effluent fractions showed the same B concentration. The process of incubation/permeation was repeated two more times. The results showed that, with the exception of a few outlier values from the Southern end of the JV, B in saturated paste or hot water extracts wasn't linearly correlated with soil salinity of the surface and subsurface samples. The reason for that was argued to be due to the anthropogenic factor of intensive agriculture that generated high demand on B as contrasted by high rate of salt accumulation in surface soil layers caused by the use of conservative irrigation systems with increasingly poor quality water. The low B levels in most samples marked the JV soils to be marginal to deficient in that nutrient. Soluble B in paste or hot water extracts followed a 1:1 relation between either fraction in surface and subsurface layers. However, the hot water extractable B was almost 4 times the corresponding levels of paste extract for both surface and subsurface samples. This implied that crop uptake of B takes place mainly from the paste extract fraction. Adsorption of B onto the three soil samples conformed to the Langmuir adsorption isotherm. These soil samples exhibited a similar affinity constant for B (0.12–0.21mL/μg), but their maximum adsorption capacity decreased in the southward direction geographically; being the highest for the Northern Shuna (39.7μg B/g soil) and the lowest for the Sweimeh (8.7μg B/g soil). The similarity of the Langmuir affinity constant reflected the similarity of clay mineralogy. In addition, the decreasing adsorption capacity was consistent with the decreasing clay content and CEC of these samples. The three soil samples showed a tendency for B regeneration while this tendency decreased with the advancement of incubation/leaching cycles. Almost half of the adsorbed B was leached from the Shuna-North soil columns as contrasted by half of that quantity for the other two samples.

Factors affecting CO2 efflux rates and the stability of soil organic carbon storage in volcanic soils of the Canary Islands

Because volcanic soils store large amounts of soil organic carbon (SOC), they play a far more important role in the carbon (C) cycle than their limited global coverage suggests. We analysed the C released as CO2 from a range of volcanic soils under natural conditions and analysed the influence of environmental variables (moisture and temperature), substrate availability (as assessed from the contents of various SOC fractions and the inputs of plant residues from litterfall), respiratory agents (roots, microorganisms and decomposing enzymes) and other pedological features of the topsoils (0–30 cm depth) on the CO2 efflux rates over a 2-year experimental period. High CO2 efflux rates (419 g C-CO2 m−2 y−1 as the average for Andisols) were obtained that were related to significant decreases in the amount of SOC stored. CO2 release was strongly controlled by soil moisture, although it was inhibited in the Andisols with the highest moisture levels (above 50 kg m−2 in topsoil). It was not responsive to the availability of decomposing microorganisms or enzymes and appeared more related to the inputs of easily decomposable plant residues than to the amount of either labile or recalcitrant SOC. Among the SOC pools, only the water-soluble C in saturated paste extracts (WSCse) of air-dried soil samples was consistently correlated with the CO2 efflux rates. The desiccation of Andisols appeared to induce the release of previously stabilised SOC, which was readily mineralised when the moisture conditions became favourable. The results of this study indicate that SOC storage in Andisols is highly vulnerable to drying-wetting processes even in unmanaged natural ecosystems and that microclimate conditions can be critical for successful C sequestration in these soils.

Spatial variability of soil electrical conductivity in a small watershed on the Loess Plateau of China

Knowledge of soil electrical conductivity of saturated paste extract (ECe) pattern is important to effectively managing farmland and improving crop productivity. The objectives of this study were (1) to characterize the spatial patterns of ECe and electrical conductivity of saturated paste (ECs) and (2) to determine the factors that affect significantly in the estimation of soil ECe. Soil samples were taken at various soil depths (0.1, 0.2, 0.4, 0.6, and 0.8m) of 124 locations in a small watershed. Besides ECe and ECs, various soil, topographical, and vegetation properties were measured. Geostatistical techniques were used to characterize the spatial patterns of ECe and ECs. Ordinary least squares (OLS) and generalized least squares (GLS) models were used to perform multiple regression analyses between ECe and other properties. The OLS model belongs to a non-spatial regression, whereas the GLS model is a spatial regression which considers the autocorrelation in the residuals. Results showed that both ECe and ECs presented moderate variability at the watershed scale. The ECe presented weak to moderate spatial dependency, whereas the ECs presented moderate to strong spatial dependency. The ratio of ECe to ECs differed with soil texture, and it was greater for sand texture than for loam texture. A fair to moderate spatial agreement existed between ECe and ECs at all depths except for 0.2m, where ECe presented a more random distribution. Heteroscedasticity in the residuals between two land uses (grass land and shrub land) and autocorrelation in the residuals only existed at 0.4m soil layer where the GLS model did not improve significantly over the OLS model in terms of explaining variations in ECe. Electrical conductivity of saturated paste was the dominant factor in explaining ECe variation for all depths, while soil separate significant affected the estimation of ECe at 0.1m as well. It is concluded that ECs may be used as a surrogate for ECe especially for homogeneous soil textures. This would greatly reduce the work involved in ECe measurement due to the easier availability of ECs. Our study implies that ECe can be used as an index of soil fertility condition in this area. In addition, OLS model can be accurate enough to describe the relationships between ECe and other properties due to the absence of strong spatial dependency of ECe in this area.

Effects of irrigation using treated wastewater on table grape vineyards: dynamics of sodium accumulation in soil and plant

The effect of using treated wastewater for irrigation of table grapes (Vitis vinifera cv. Superior Seedless) was studied for six seasons. The experimental vineyard was grown on clay loam soil in a semi-arid area. Treated wastewater (5.83 meq L−1 Na+) with (TWW + F) and without (TWW) fertilizer, and fresh water with fertilizer (FW + F, 2.97 meq L−1 Na+), were each applied at three irrigation levels (80, 60 and 40 % of crop evapotranspiration before harvest). Root zone (0–60 cm soil depth) soil saturated paste extract Na+ concentrations and sodium adsorption ratio (SAR) values fluctuated over the years, but generally decreased in the order TWW > TWW + F > FW + F for each irrigation level. Both Na+ concentrations and SAR values developed faster and to a greater extent at higher irrigation. Adding fertilizer to TWW decreased Na+ and SAR only at the high irrigation level. Na+ concentrations in the trunk wood, bark and xylem sap of the TWW and TWW + F irrigated vines were significantly higher than those in the FW + F-irrigated vines. Leaf petiole Na+ content increased with time and its maximum value in TWW and TWW + F irrigated vines exceeded 6,500 mg kg−1, threefold higher than in FW + F irrigated vines. We conclude that in clay soils under relatively high irrigation, Na+ may pose a greater potential risk to plants and soil rather than Cl− or salinity per se. However, significant effects on yield were not recorded during this six-year study probably due to the high salinity tolerance of the ‘Paulsen’ rootstock used in the experiment.

A comparison of salinity measurement methods based on soil saturated pastes

Soil salinization is of great concern in the irrigated arid and semi-arid western U.S. due to its threat to sustainable agricultural productivity and thus is closely monitored. The measurement of electrical conductivity in saturated paste extracts (ECe) is the standard to which other salinity estimation methods are referenced. Since this method is laborious, the preparation of saturated pastes subject to bias, and salinity estimates by electrical conductivity (EC) subject to chemical artifact, numerous other methods have been proposed. These include EC measurements in diluted saturated paste extracts (ECed), direct measurement of EC in soil pastes (“Bureau of Soils Cup” method, ECcup), and EC based on electromagnetic induction (ECH25ECe). The main objective of this paper is to compare these four saturated paste-related methods of estimating salinity with respect to specific soil management goals. Comparison of the methods across six soil depths and three textural groups demonstrates that estimates of salinity are significantly influenced by the method, depth of sampling, and soil texture. Whereas ECe and ECcup estimates differed significantly from each other and from those of the other methods, ECH25ECe and ECed estimates were similar. In addition, high correlations between estimates of salinity by ECH25ECe and ECe indicate their similarity and suggest the suitability of the ECH25ECe method as a reference parameter for monitoring salinity. Thus, the suitability of the ECH25ECe method is drawn from its similarity to 1) the superior ECed method, which corrects for salinity underestimation due to ion pair formation, and 2) the ECe method, which is the standard method against which other salinity estimates are traditionally compared. This finding was consistent across all depths, the three texture groups, and the combinations of method and depth or texture groups. The high coefficient of variation in ECe and ECcup highlights the subjectivity of these methods and raises questions about the choice of ECe as standard for salinity estimates. These results therefore suggest that the ECH25ECe method (which requires few collocated but representative ECe measurements) be used to rapidly and reliably monitor salinity in calcareous soils of arid and semiarid regions.

Influence of soil on groundwater geochemistry in a carbonate aquifer, southern Italy

The role of soil compositions in influencing groundwater geochemistry in carbonate aquifers is still little known. Nothing is known regarding the influence of pyroclastic soils (andisol) within the carbonate Apennines in central-southern Italy, despite their wide distribution. In this study we analyze some physical and chemical properties of pyroclastic soil at the Acqua dei Faggi experimental site (southern Italy), to assess its influence on groundwater geochemistry. Chemical analyses were carried out on saturated paste extracts and a physical analogue model was developed through two column experiments. Physico-chemical properties of rainwater and spring water, and some microbiological features of the soil medium were also taken into consideration. The studied soil has a great influence in modifying rainwater chemistry during percolation. About the 50% of HCO 3 and Ca 2+ in spring water is due to interaction between percolation water and soil medium, and equilibrium with calcite is reached at this stage. The Na + /K + ratio is buffered by clay minerals in the soil by primary silicates in the pyroclastic cover. Cl and SO 4 2concentrations in spring water are very close to that of soil infiltration water during short-term interaction with soil, but a decline is showed during long-term cause to the anions adsorption effect in the andisol. Chemical and microbiological investigations show the existence of a soil microbial community that allows denitrification and nitrate reduction. Infiltration processes cause anoxic conditions within the soil medium, therefore the absence of NH 4 + in spring water throughout the observation period should be due to anammox processes. These findings suggest that hydrochemistry and spring chemographs may be significantly influenced by several factors, such as relationships between soil and rainwater, vegetation, and microbial communities, which are not necessarily correlated with lithological and structural features of carbonate aquifers.