Influence Of Soil Salinity Research Articles

Calibration of Capacitance Probe Sensors in a Saline Silty Clay Soil

Capacitance probe sensors are a popular electromagnetic method of measuring soil water content. However, there is concern about the influence of soil salinity on the sensor readings. In this study capacitance sensors are calibrated for a saline silty clay soil. An electric circuit model is used to relate the sensor's resonant frequency F to the permittivity (ε) of the soil. The circuit model is able to account for the effect of dielectric losses on the resonant frequency. Dielectric mixing models and empirical models are used to relate the permittivity to the soil water content (θ). The results show that the electric circuit model does not fit the F–ε(θ) data if the calibrated bulk electrical conductivity (EC) model is used. The dielectric losses are overestimated. Increasing the exponent c in the tortuosity factor of the bulk EC model and thereby lowering the bulk EC and the dielectric losses improves the performance of the model. Measured and calculated volumetric water contents compare reasonably well (R2 = 0.884). However, only 73 out of 88 data points can be described. The rejected points are invariably at high water contents where the high dielectric losses result in the sensor frequency being insensitive to ε(θ).

Calibration of Capacitance Probe Sensors using Electric Circuit Theory

Capacitance probe sensors are an attractive electromagnetic technique for estimating soil water content. There is concern, however, about the influence of soil salinity and soil temperature on the sensors. We present an electric circuit model that relates the sensor frequency to the permittivity of the medium and that is able to correct for dielectric losses due to ionic conductivity and relaxation. The circuit inductance L is optimized using sensor readings in a modified setup where ceramic capacitors replace the sensor's capacitance plates. The three other parameters in the model are optimized using sensor readings in a range of nonconductive media with different permittivities. The geometric factor for the plastic access tube gp is higher than the geometric factor for the medium gm, indicating that most of the electromagnetic field does not go beyond the access tube. The effect of ionic conductivity on the sensor readings is assessed by mixing salts in three of the media. The influence is profound. The sensor frequency decreases with increasing conductivity. The effect is most pronounced for the medium with the lowest permittivity. The circuit model is able to correct for the conductivity effect on the sensors. However, as the dielectric losses increase, the frequency becomes relatively insensitive to permittivity and small inaccuracies in the measured frequency or in the sensor constants result in large errors in the calculated permittivity. Calibration of the capacitance sensors can be simplified by fixing two of the constants and calculating the other two using sensor readings in air and water.

Calibration of Capacitance Probe Sensors using Electric Circuit Theory

Capacitance probe sensors are an attractive electromagnetic technique for estimating soil water content. There is concern, however, about the influence of soil salinity and soil temperature on the sensors. We present an electric circuit model that relates the sensor frequency to the permittivity of the medium and that is able to correct for dielectric losses due to ionic conductivity and relaxation. The circuit inductance L is optimized using sensor readings in a modified setup where ceramic capacitors replace the sensor's capacitance plates. The three other parameters in the model are optimized using sensor readings in a range of nonconductive media with different permittivities. The geometric factor for the plastic access tube gp is higher than the geometric factor for the medium gm, indicating that most of the electromagnetic field does not go beyond the access tube. The effect of ionic conductivity on the sensor readings is assessed by mixing salts in three of the media. The influence is profound. The sensor frequency decreases with increasing conductivity. The effect is most pronounced for the medium with the lowest permittivity. The circuit model is able to correct for the conductivity effect on the sensors. However, as the dielectric losses increase, the frequency becomes relatively insensitive to permittivity and small inaccuracies in the measured frequency or in the sensor constants result in large errors in the calculated permittivity. Calibration of the capacitance sensors can be simplified by fixing two of the constants and calculating the other two using sensor readings in air and water.

Calibration of Capacitance Probe Sensors in a Saline Silty Clay Soil

Capacitance probe sensors are a popular electromagnetic method of measuring soil water content. However, there is concern about the influence of soil salinity on the sensor readings. In this study capacitance sensors are calibrated for a saline silty clay soil. An electric circuit model is used to relate the sensor's resonant frequency F to the permittivity (ε) of the soil. The circuit model is able to account for the effect of dielectric losses on the resonant frequency. Dielectric mixing models and empirical models are used to relate the permittivity to the soil water content (θ). The results show that the electric circuit model does not fit the F–ε(θ) data if the calibrated bulk electrical conductivity (EC) model is used. The dielectric losses are overestimated. Increasing the exponent c in the tortuosity factor of the bulk EC model and thereby lowering the bulk EC and the dielectric losses improves the performance of the model. Measured and calculated volumetric water contents compare reasonably well (R2 = 0.884). However, only 73 out of 88 data points can be described. The rejected points are invariably at high water contents where the high dielectric losses result in the sensor frequency being insensitive to ε(θ).

Influence of soil salinity on the populations and composition of fluorescent pseudomonads in plant rhizosphere

Abstract Effect of soil salinity associated with intensive cultivation including horticulture on microbial communities in the soil-root system was investigated in a growth chamber experiment. Spinach plants were grown on three soil samples of the same origin but with low, medium, and high levels of salinity. Microbial populations, including fluorescent pseudomonads, in three sites of the soil-root system, namely root-free soil, rhizosphere soil, and rhizoplane, of 3-week-old spinach plants were compared in relation to the levels of soil salinity. Effect of soil salinity on the microbial populations differed widely among the three sites of the soil-root system, as well as among the microbial groups. In the root-free soil, populations of total bacteria (TB) and gram-negative bacteria (GN) did not change significantly through salinity, while the populations of total fluorescent pseudomonads (FP) apparently increased. In the rhizosphere soil, however, soil salinity induced changes in the populations depending...

Influence of Soil Salinity on Production of Dry Matter and Uptake and Distribution of Nutrients in Barley and Corn: I. Barley (Hordeum vulgare L.)1

AbstractThe production of dry matter and the uptake and concentration of nutrients by barley (Hordeum vulgare L.) from soil adjusted to different levels of salinity with a mixture of salts were evaluated in a greenhouse study. Following germination of the plants, soil salinity levels ranging from EC values of 0 to 30 mmhos/cm of the soil solution at field capacity were induced by additions of a salt solution containing one part Na2SO4, one part MgSO4, and one part CaCl2. During the growth period of 98 days, increasing soil salinity increased sulfate‐S and chloride in the saturation extract and lowered soil pH. Exchangeable Na, Mg, and Ca increased markedly while exchangeable K and available P increased only slightly. Acid‐extractable Mn increased, but there was little or no effect on acid‐extractable Zn, Fe, and Cu. Production of dry matter by the vegetative parts and grain heads of barley increased up to an EC of 12, then decreased at salinity levels above this value. Coefficients of correlation indicate significant negative relationships between soil salinity and uptake of P, K, Ca, Fe, and Cu by the vegetative parts and grain heads of barley. Conversely, significant positive correlations occur between soil salinity and uptake of Mn and Na by barley.

Influence of Soil Salinity and 2, 4-D Treatments on Establishment of Desert Wheatgrass and Control of Halogeton and Other Annual Weeds

Influence of Soil Salinity and 2, 4-D Treatments on Establishment of Desert Wheatgrass and Control of Halogeton and Other Annual Weeds