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Cómo conocer la salinidad del suelo mediante medidas de conductividad eléctrica
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La medida de la conductividad eléctrica a 25 ºC (CE25) de la solución del suelo, de un extracto acuoso de este, o del mismo suelo, es el fundamento de varios métodos para la evaluación de su salinidad. El objetivo de las mediciones de CE25 en la agricultura es estimar el estrés salino sobre la planta y servir así de base para la planificación de un manejo que contrarreste los efectos de la salinidad en la producción del cultivo. En el presente trabajo se revisan los diferentes métodos al alcance de agricultores, técnicos y consultores agrícolas para evaluar la salinidad de los suelos mediante medidas de CE25. Se ofrecen asimismo, pautas generales para una correcta realización e interpretación de las mediciones, y se citan las fuentes documentales (libros, páginas web, etc.) donde los métodos para hacer dichas mediciones se describen con más detalle.
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... In the aqueous extracts the EC 25 was measured with a Basic 30 conductimeter equipped with a Pt 1 cm −1 5070 conductivity cell (Crison Instruments, Barcelona, Spain) and, the chloride content determined with the above-mentioned coulometric-amperometric argentometry method (Cotlove, 1963). The soil salinity and chloride content were finally expressed as their values in the saturation extract (EC se and [Cl − ] se ) by multiplying the EC 25 and [Cl − ] in the 1:1.5 extracts by an adequate transformation coefficient (Visconti and de Paz, 2018) which depends on the soil clay content and whose values ranged from 1.60 to 1.67 in this case. ...
The melon crop is moderately sensitive to soil salinity and, as a consequence, its yield decreases under saline conditions. Nevertheless, the exposure to moderate salinity also influences the melon quality by improving it, which offers compensation to the farmer. As a consequence, in moderately salt-affected lands, like the traditional irrigation area of the ‘Vega Baja del Segura’ (Alicante, Spain), melons are being grown. In this area the modernization of the secular irrigation system through the replacement of flood by drip systems, is currently being fostered. This fact, however, is generating some controversy, due to the known salt leaching effect that flood irrigation followed by drainage makes in the soil. In this study, the effects of three irrigation systems, namely, drip (DI), subsurface drip (SDI) and flood (FI), on soil salinity and thus, on the yield and quality of the melon, were compared. According to the results, the FI system kept the soil salt levels during the growth period at 4.1 ± 0.3 dS/m, that is, significantly lower than the 4.7 ± 0.2 dS/m attained with the DI and SDI systems. Nevertheless, the DI and, overall, SDI, provided higher and more homogenous soil moisture completely counteracting the effect of salinity as revealed by the soil water potential calculations. As a result, the SDI gave
27 ± 5 Mg/ha of total yield in comparison to 23 ± 2 Mg/ha (DI) and 20 ± 6 Mg/ha (FI). Besides, the SDI system reduced the number of damaged melons, thus additionally contributing to the significant higher marketable yield of the SDI (25 ± 4 Mg/ha) in comparison to the DI (20 ± 1 Mg/ha) and the FI (19 ± 7 Mg/ha). On the contrary, in the SDI treatment the fruit soluble solids content, tritatable acidity and pulp firmness decreased a bit, however, in the sensory evaluation no differences among irrigation treatments were observed.
Las vinazas de mezcal son residuos líquidos recalcitrantes con alta carga orgánica y elementos disueltos, la cual puede ser utilizada en la nutrición de plantas. El objetivo del trabajo fue evaluar la toxicidad de las vinazas del mezcal en la germinación de semillas y su efecto biofertilizante en el rendimiento de hortalizas. Se realizaron dos experimentos en lechuga, tomate y pepino: 1) prueba de fitotoxicidad en la germinación en semillas con diferentes concentraciones de vinaza (2.5, 5, 10, 20, 40, 80 y 100%); y 2). Se evaluó el efecto biofertilizante de las combinaciones de 100-0, 80-20, 40-60 y 20-80% de vinaza y solución nutritiva Steiner, y como testigo el 100% de la solución nutritiva; en ambos experimentos se utilizó un diseño completamente al azar. La concentración del 2.5% de vinaza del mezcal, fue tóxica para las semillas de lechuga y más del 10% inhibió su germinación. Para semillas de tomate el 20% resultó tóxico, mientras que en semillas de pepino provocó hormesis. La concentración del 80% de vinazas inhibió la germinación en semillas de tomate. La combinación: 40 + 60% de vinaza y solución nutritiva aplicados en la nutrición de lechuga y tomate, alcanzó los máximos valores de todas las variables evaluadas. En pepino, el rendimiento disminuyó de forma lineal al aumentar el porcentaje de vinaza como complemento de la solución nutritiva.
Observed variations in the ground electrical conductivity (σb*) measurements obtained with EMI instruments depend on several soil proxies that influence crop growth and development such as salinity (σe), contents of water (θw), clay (wc) and organic matter (wom) and bulk density (ρb). However, the relative contributions of all these to σb* are unknown. This knowledge is needed to improve the planning and interpretation of σb* data for precision agriculture applications. Recently, a semi-empirical model has been developed to relate σb* measurements taken with an EM38 device to σe, θw, wc, wom and ρb and also soil temperature (t). In this work this model was subjected to a global sensitivity analysis (GSA) based on the soil data obtained during two surveys carried out, one in summer and the other in autumn, in an ample irrigated area in SE Spain. On the basis of the multiple linear regression meta-models developed for the σb* measurements, these were found to linearly respond to the soil properties (R² between 0.92 and 0.96) and thus, the GSA could be based on their standardised regression coefficients. According to these, the soil characteristics explain the following percentages of variance in σb* (PV): 30–34 (σe), 8–20 (θw), 32–47 (wc), 0.6–2.6 (wom), 5.7–7.5 (ρb) and 0.3–0.4 (t) with changes from the summer to the autumn season of − 4, − 12 and + 15 in the PV explained by the most influential properties, respectively, σe, θw and wc. The results of the GSA will help the planning and interpretation of σb* measurements for improving crop management.
Electromagnetic induction (EMI) measurements (σb*) are widely used for the survey of several soil attributes, among which basic properties such as salinity (σe), water content (θw), clay (wc), organic matter (wom) and bulk density (ρb) stand out. In usual practice, purely empirical models relating one of these properties to σb* are calibrated at selected sites. However, this calibration is site and time specific and has to be repeated time and again. In order to understand where the variability of the EMI empirical models comes from, it is necessary to know how the different soil properties contribute to them and, with this aim, a more physically based relationship between σb* and, at least, σe, θw, wc, wom and ρb was developed in this work, additionally including soil temperature (t). It was calibrated and cross‐validated with the data from one survey carried out in a wide agricultural irrigation area in SE Spain, taking σb* measurements with the Geonics EM38 in the horizontal and vertical dipole modes and at various heights over the ground. Then, it was externally validated with the data from a second survey carried out 4 years later in the same area but in a different season. In the calibration, R² and root mean square error (RMSE) were 0.84 and 0.18 dS m⁻¹ (41%), respectively, for the vertical dipole orientation and 0.90 and 0.11 dS m⁻¹ (39%) for the horizontal one. In the external validation, R² and RMSE were 0.80 and 0.24 dS m⁻¹ (44%), respectively, for the vertical dipole orientation and 0.90 and 0.13 dS m⁻¹ (38%) for the horizontal one. Therefore, because the performance of the model barely worsened as time passed by, it can be considered to represent the underlying physical process and, therefore, to increase our understanding of how the soil EMI signals are generated, with potential benefits for the planning and comparability of EMI soil measurements, specifically with the EM38, among different areas.
Highlights
• A semi‐empirical model was developed to predict soil EMI measurements from basic ground properties.
• Salinity, water content, clay, organic matter, bulk density and temperature were used as predictors.
• The model was able to explain between 80 and 90% of the variance in EMI measurements in the validation.
• This model helps us understand how the basic soil properties contribute to the EMI measurements.
Soil interstitial waters are an extremely important facet of many
environmental studies. The biogeochemical cycles of important nutrients,
metal migration across the landscape, and pollutant movement to
groundwater are highly affected by the water flow characteristics in
soils and sediments. The purpose of this review is to evaluate the
various soil solution sampling techniques. There is no single device
that will perfectly sample soil solution in all conditions encountered
in the field; hence a critical literature review on the different soil
solution samplers is given. The differences among the various soil
solution samplers and their relative advantages and limitations are
discussed. The problems involved in using these samplers are assessed
and plausible solutions are presented.
A new model described the relation between bulk soil electrical conductivity (ECa), volumetric content (θw) and electrical conductivity of soil water (ECw) is given along with supporting evidence for its validity. The new model distinguishes between the water and salt present in the soil in the "immobile' (fine pores) and "mobile' (large pores) phases. It provides a possible physical meaning to the transmission coefficient (T) previously used in an earlier model and eliminates a limitation of that which existed under conditions of low salinity. -from Authors
An extensive literature review of all available salt tolerance data was undertaken to evaluate the current status of our knowledge of the salt tolerance of agricultural crops. In general, crops tolerate salinity up to a threshold level above which yields decrease approximately linearly as salt concentrations increase. Our best estimate of the threshold salinity level and yield decrease per unit salinity increase is presented for a large number of agricultural crops. The methods of measuring appropriate salinity and plant parameters to obtain meaningful salt tolerance data and the many plant, soil, water, and environmental factors influencing the plant's ability to tolerate salt are examined.
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