Conductivity Of Saturated Paste Extract Research Articles

Spatial and temporal trends in soil salinity for identifying perched and deep groundwater systems

AbstractCharacterization of spatial and temporal variability in water flow and solute transport to foster better land management in salt‐affected landscapes requires direct hydrological observation, for example using suites of nested piezometers and dip wells. Such methods are costly to install and produce data with low spatial density, so are not ideal for supporting within‐field scale land management decisions. We present a new methodology to characterize water‐flow systems in salt‐affected landscapes using trends in shallow (<1 m) down‐profile soil salinity based on electrical conductivity of saturated paste extract (ECse) and salts (that is the water extractable major ions of Ca, K, Mg, Na, P, Cl and S mg/kg) from a range of topographic settings. This involved coupling seasonal (late winter and late summer) salinity trends with clay percent (for soil morphology) and terrain patterns to understand the connectivity between perched and deep groundwater systems in a 120 ha catchment in the Mount Lofty Ranges, South Australia. From investigations at 19 sites in the catchment comprising toposequences or paired sites (in close proximity, but in different topographic settings), soil salinity trends revealed four hydro‐pedological systems: (i) a perched freshwater system with no hydraulic connectivity to the deep groundwater in upper slopes, (ii) an intermediate system comprising perched freshwater connected to a deep groundwater system in mid and upper slopes, (iii) a deep groundwater system in upper slopes, and (iv) a deep groundwater system in lower slopes. Although most of the 19 sites proved non‐saline, seasonal changes in ECse and ion concentration along with topography and soil morphology were sufficient to characterize the hydro‐pedological systems. We assigned these systems to a newly developed salinity classification based on dominant soil‐regolith‐hydrological processes and designed to support land management decisions. Conceptual hydro‐pedological models for each system were constructed to illustrate and explain the important interactions in each and how these relate to the new salinity classification. We propose that the methodology based on seasonal monitoring offers a new approach to landscape‐based hydro‐pedological characterization without reliance on the traditional groundwater monitoring methods. The new method offers wider access to catchment hydro‐pedological information to support better land management decisions in sloping landscapes subject to salinity.

Effect of saline water on cucumber (Cucumis sativus L.) yield and water use under drip irrigation in North China

Saline water has been included as an important substitutable resource for fresh water in agricultural irrigation in many fresh water scarce regions. In order to make good use of saline water for agricultural irrigation in North China, a semi-humid area, a 3-year field experiment was carried out to study the possibility of using saline water for supplement irrigation of cucumber. Saline water was applied via mulched drip irrigation. The average electrical conductivity of irrigation water (ECiw) was 1.1, 2.2, 2.9, 3.5 and 4.2 dS/m in 2003 and 2004, and 1.1, 2.2, 3.5, 4.2 and 4.9 dS/m in 2005. Throughout cucumber-growing season, the soil matric potential at 0.2 m depth immediately under drip emitter was kept higher than −20 kPa and saline water was applied after cucumber seedling stage. The experimental results revealed that cucumber fruit number per plant and yield decreased by 5.7% per unit increase in ECiw. The maximum yield loss was around 25% for ECiw of 4.9 dS/m, compared with 1.1 dS/m. Cucumber seasonal accumulative water use decreased linearly over the range of 1.5–6.9% per unit increase in ECiw. As to the average root zone ECe (electrical conductivity of saturated paste extract), cucumber yield and water use decreased by 10.8 and 10.3% for each unit of ECe increase in the root zone (within 40 cm away from emitter and 40 cm depths), respectively. After 3 years irrigation with saline water, there was no obvious tendency for ECe to increase in the soil profile of 0–90 cm depths. So in North China, or similar semi-humid area, when there is no enough fresh water for irrigation, saline water up to 4.9 dS/m can be used to irrigate field culture cucumbers at the expense of some yield loss. © 2010 Published by Elsevier B.V.

Avaliação de solos sob diferentes períodos de aplicação com vinhaça

O objetivo deste estudo foi avaliar as alterações físico-químicas associadas à profundidade e respectivas correlações em solos sob diferentes períodos de fertirrigação com vinhaça. Para isto foram selecionadas na Usina Santa Tereza, PE, quatro áreas: Área 1, com 3 anos sob fertigação com vinhaça; Área 2, com 7 anos; Área 3, com 15 anos e Área 4, sem aplicação de vinhaça. Em cada uma das áreas foram marcados 20 pontos com distância de 10 m, georreferenciados, formando uma malha e coletadas amostras de solo nas profundidades de 0-10, 10-20 e 20-40 cm. Após a amostragem o solo foi secado ao ar, destorroado e peneirado para realização de análises granulométricas: areia, silte e argila e físico-químicas: Ca, Mg, K, Na, trocável, pH (1:2,5 solo:água) e condutividade elétrica (CEes) no extrato da pasta saturada. O grau de correlação linear simples entre os pares de dados foi determinado pelo coeficiente de correlação de Pearson. Os resultados obtidos mostraram correlação entre profundidade e demais variáveis em todas as áreas em estudo tornando evidente que a aplicação de vinhaça altera a concentração dos cátions, de acordo com as características dos solos e o manejo de cada área.

Effect of Spent Mushroom Substrate on Seed Germination of Cool-season Turfgrasses

Spent mushroom substrate (SMS) is used by the turf industry in the northeastern United States for soil improvement. When tilled into soil at high rates, some turfgrass managers claim that SMS inhibits turf seed germination. The authors’ objectives were 1) to determine whether fresh SMS inhibits turf seed germination and, if so, which species are most adversely affected; 2) to evaluate whether any inhibition incited by SMS is the result of osmotic effects or toxicity of compounds in SMS extracts; 3) to determine whether any negative effect of SMS on germination can be eliminated by leaching the SMS-amended soil before seeding; and 4) to assess the performance of SMS on seedling emergence in the field. Germination of nine turfgrass species was evaluated in mixtures made from fresh SMS (electrical conductivity of saturated paste extract = 11.9 dS·m−1) and a loamy sand soil. Germination inhibition resulting from SMS was most pronounced in the following order: Colonial bentgrass (Agrostis capillaris L.) > sheep fescue [Festuca ovina L. ssp. hirtula (Hackel ex Travis) Wilkinson] > Kentucky bluegrass (Poa pratensis L.) > hard fescue [Festuca trachyphylla (Hackel) Krajina] > creeping bentgrass (Agrostis stolonifera L.) > chewings fescue [Festuca rubra L. sp. commutata (Thuill.) Nyman] = strong creeping red fescue (Festuca rubra L. ssp. rubra Gaud.) > slender creeping red fescue [Festuca rubra L. sp. litoralis (Meyer) Auquier] > perennial ryegrass (Lolium perenne L.). SMS had a stronger negative effect on germination rates than on final germination percentages. Germination of perennial ryegrass and Kentucky bluegrass on blotter paper moistened with SMS extracts or polyethylene glycol of equivalent osmotic potentials showed that the inhibition was primarily the result of osmotic effects. In an experiment with a 50% soil/50% SMS (v/v) mixture, Kentucky bluegrass germinated better in pots that had been watered with 133% or 167% of the evaporation rate for 10 days prior to seeding than in unleached pots. Although the negative effect of SMS on seed germination was not confirmed in a field study in which ECe values never exceeded 4.1 dS·m−1, the authors conclude that incorporation of high rates of SMS represents a potential problem for turfgrass establishment.

Straw Management Effects on Organic Matter Mineralization and Salinity in Semiarid Agricultural Soils

The impact of straw incorporation (6 Mg ha -1 year -1 ) into agricultural soils compared with straw removal on organic matter mineralization and salinity was studied. The mineralization coefficient (CO 2 -C evolved/organic C ratio) was obtained to evaluate organic matter mineralization. Soil salinity was measured as means of electrolytic conductivity of saturation paste extract. Both parameters were measured seasonally during two years in two salt-affected soils of the semiarid Central Ebro Valley (northeast Spain), a saline soil and a saline-sodic soil. The electrolytic conductivity (ranging from 2.5 dS m -1 to 24.3 dS m -1 ) and the mineralization coefficient (ranging from 5.9 10 -4 day -1 to 37.9 10 -4 day -1 ) varied widely during seasonal samplings of both soils. The lowest electrolytic conductivity values, coincided with the highest mineralization coefficient values. Straw mulching and burying decreased significantly the average seasonal electrolytic conductivity of both soils: 2.5 times in the saline soil, and 1.9 times in the saline-sodic soil. The EC reduction only increased significantly (P < 0.05) the mineralization coefficient on saline soil (1.6 times). Straw amendment, followed by rainy periods, allowed the soluble salts leaching but did not modify significantly sodium content. A logarithmic regression was found between mineralization coefficient and electrolytic conductivity (r 2 = 0.41), considering both soils. Infiltration, water aggregate stability, and qCO 2 were improved with the straw amendment, but only in saline soil. Soil differences showed the existence of a double effect: an osmotic and a specific ion effect.

Theoretical and Experimental Performance of Spatial Interpolation Methods for Soil Salinity Analysis

Interpolation methods are required for analysis of soil salinity data by geographic information systems. This study was conducted to determine interpolation methods that are best suited to map soil salinity. Methods of closest neighbor, kriging, inverse-distance moving average, and thin plate smoothing splines were compared by cross-validation for precision and smoothing, using 341 measured values of electrical conductivity of saturated paste extract in a 16 000 ha area in southwest Iran. Interpolation precision of all methods were low, with a mean absolute difference between measured and predicted values ranging from 42 to 76% of the mean measured soil salinity. This was due to the large ratio of nugget effect to the sill of the variogram and to the high variability of data. Thin plate smoothing splines and ordinary kriging were the most precise methods, whereas closest neighbor was the least precise. The smoothing of the methods was assessed by comparing the dispersion standard deviation of interpolated values with that of observed values. The most precise methods were also those that performed an important smoothing. Ordinary kriging and thin plate smoothing splines produced contour maps that were much easier to interpret. A theoretical analysis of the performance of the methods (precision and smoothing) led to conclusions similar to those based on the cross-validation study. Such a theoretical analysis can be used to select an appropriate interpolation method without the need for time consuming cross-validation.

Conjunctive use of saline and non-saline waters. I. Response of wheat to initial salinity profiles and salinisation patterns

Response of wheat ( Triticum aestivum L.) to salinity stress at different growth stages and patterns of salinisation was studied in microlysimeters. The treatments consisted of variable initial salinity profiles (salinity increasing, decreasing and uniform with depth) in combination with different salinisation patterns achieved through irrigations with waters of increasing, constant, decreasing salinity, alternating saline and non-saline, introducing saline waters after jointing, keeping the total salt input through these irrigations the same. Almost 3-fold variations in wheat yields were observed. In soil where initial salinity increased with soil depth, yields were markedly improved (30–36%) compared with the soils having uniform or inverted salt profiles. Similarly, shifting to saline irrigation at jointing, cyclically non-saline/saline water or increasing salinity, outyielded the others. Interestingly, lowest yields were obtained in soils receiving constant salinity waters. Amongst the various indices of salinity, yields were best related ( r = −0.78) to root length weighted salinity over different periods of growth. Independent estimates of salinity responses showed the tolerance of wheat to increase with ontogeny. The EC 50 values (electrical conductivity of saturation paste extract for 50% yields) increased to 9.3, 10.8 ± 0.1, 12.7 and 13.2 dS/m for periods between sowing to crown rooting, crown rooting to boot, boot to dough and dough stage to maturity, respectively. Results imply that for nonsteady state conditions such as those prevailing under monsoonal climate, the salt tolerance at critical stages of crop plants, changes in responses to salinity with modes of salinisation and initial distribution of salts need to be considered for effective use of multisalinity waters.

Estimating the electrical conductivity of saturated paste extracts from 1:5 soil, water suspensions and texture

This paper presents a method of estimating the electrical conductivity (EC) of a saturated paste extract (ECe) from the EC of a 1 to 5 soil/water suspension (EC1:5) and an estimate of soil texture. The method has application in soil testing laboratories which routinely determine EC1:5 but not ECe. The method of preparing the saturated paste by capillary wetting is also compared with the standard method of hand mixing. The coefficient (f) relating ECe to EC1:5, i.e. ECe = fEC1:5 was found to be related to the water content of the saturated paste (�SP kg/kg) by f = 2.46 + 3.03/QSP. The relationship between �SP and texture, determined by hand working, indicates that the uncertainty associated with use of this relationship could be significant in sandy soils. Wetting the soil by capillarity rather than by hand mixing resulted in a lower saturation percentage and higher ECe but dissolved the same amount of salts. The capillary wetting method is preferred as it greatly reduces labour time.

Application of a Conceptual Model to Irrigation Water Requirement and Salt Tolerance of Crops

AbstractA theoretical model describing crop yield response to water quantity and quality under irrigation conditions is generalized to obtain soil‐water‐salt regimes, water requirement, and salt tolerance curves. Theoretical results show that under continuous irrigation conditions steady water and salt regimes may be achieved only when application water quantities exceed seasonal class A pan evaporation (E0) by &gt;50%. The effects of water quantity and soil salinity on crop yield and the shape of the response curves to electrical conductivity of saturated paste extracts are similar for measured data and simulated results. In both, salt tolerance curves of wet irrigation regimes (irrigation quantity &gt;E0) have maximum relative yield (YR) of one, while for dry irrigation regimes (irrigation quantity &lt;0.8. E0), YR &lt;1.0. Explanation of salt tolerance curves is attempted.

EFFECTS OF SULPHATE AND CHLORIDE SOIL SALINITY ON GROWTH AND NEEDLE COMPOSITION OF SIBERIAN LARCH

Greenhouse and field studies were conducted to assess the salinity tolerance of Siberian larch (Larix siberica L.) under conditions found on the Canadian prairies. In greenhouse studies top and root growth of Siberian larch seedlings began to decline under sulphate salinity between 2.0 and 5.3 mmhos/cm (electrical conductivity of saturation paste extract) indicating that Siberian larch is moderately salt-tolerant. The addition of chloride caused an initial top growth decrease, chlorosis, and reduction in survival between 1.4 and 3.6 mmhos/cm; the latter salinity level being associated with 20 meq/L of Cl and 1.5% Cl in the saturation paste extract and needles, respectively. Field studies conducted under naturally occurring sulphate salinity indicated that height of 10-yr-old Siberian larch began to decline between 3.5 and 4.0 mmhos/cm. Changes in needle mineral composition were related to the ratio or increase of ions in the soil solution, and the physiological effect of the sulphate and chloride anion. In general, presence of chloride salinity caused a greater increase to occur in the cation content of the needles than sulphate salinity. Accumulation of organic anions in the needles was also related to cation concentration and needle chlorosis.

Measurement of Apparent Electrical Conductivity of Soils by an Electromagnetic Induction Probe to Aid Salinity Surveys

AbstractA noncontacting soil resistivity probe, based on electromagnetic induction, was used to measure soil salinity. Good correlations were obtained between the apparent bulk soil conductivity measured by the instrument and the electrical conductivity of saturated paste extracts or the bulk electrical conductivity measured by the Wenner four‐probe method. The electromagnetic induction technique provided less detailed information on salinity changes with depth than the other methods, but was faster and can provide a continuous record of salinity changes along a transect.

The effect of soil: Water ratios on the agronomic significance of the electrical conductivity of saturated paste extracts

Abstract A correction is proposed for the evaluation of salinity effects on the basis of the electrical conductivity of saturated paste extracts. It is suggested that the dilution of the soil solution during the preparation of the saturated paste must be taken into account. Equations for estimating the electrical conductivity of a soil solution at field capacity are presented. The corrected equations improve the ability to predict the salinity hazard by determining the electrical conductivity of saturated paste extract.