Apparent electrical conductivity (ECa) as a surrogate for neutron probe counts to measure soil moisture content in heavy clay soils (Vertosols)

Soil Research ◽  
2014 ◽  
Vol 52 (4) ◽  
pp. 373 ◽  
Author(s):  
John N. Stanley ◽  
David W. Lamb ◽  
Gregory Falzon ◽  
Derek A. Schneider
Keyword(s):  
Electrical Conductivity ◽  
Soil Surface ◽  
Field Capacity ◽  
Wetting Front ◽  
Site Specific ◽  
Neutron Probe ◽  
South Wales ◽  
Moisture Extraction ◽  
Apparent Electrical Conductivity ◽  
A Site

Site-specific measurements of the apparent electrical conductivity (ECa) of soil using the EM38 were correlated with near-simultaneous neutron probe readings over periods of moisture extraction by an irrigated cotton crop. Thirty sites were monitored from three ECa zones within a 96-ha field of grey Vertosol soil 30 km west of Moree, New South Wales, Australia. This study differs from previous approaches by reporting the effect on ECa of a wetting front (irrigation) reaching a single ECa measurement point in a field and by using polyethylene neutron probe access tubes so that the EM38 could be operated directly over the same site measured by a neutron probe. We report strong correlations (r = 0.94) between neutron probe counts (CRR) averaged to a depth of 40 or 60 cm and ECa from an EM38 held in the vertical mode 20 cm above the soil surface. All combinations of EM sensor height (0–1.2 m) to neutron probe measurement depth (0.2–1.4 m) returned correlations >0.85. The relationship between CCR and ECa was linear for the purposes of estimating water content over a range of background ECa levels. More critical modelling suggested a slight curve (logarithmic model) fitted best. The range of surface-surveyed ECa from the start of irrigation (refill point) to fully irrigated (full point) was ~27 mS m–1 for this Vertosol, where surface ECa readings typically ranged from 50 to 200 mS m–1. We suggest that the calibration of ECa to CRR might be effected by a two-point measurement of the soil, namely at both upper (field capacity) and lower (wilting point) ECa values, and a site-specific calibration template generated by extending these point measures to whole-field surveys.

Delineation of management zones with measurements of soil apparent electrical conductivity in the southeastern pampas

2013 ◽  
Vol 93 (2) ◽  
pp. 205-218 ◽  
Author(s):  
Nahuel Raúl Peralta ◽  
José Luis Costa ◽  
Mónica Balzarini ◽  
Hernán Angelini
Keyword(s):  
Electrical Conductivity ◽  
Soil Properties ◽  
Stepwise Regression ◽  
Clay Soil ◽  
Crop Yields ◽  
Management Strategies ◽  
Site Specific ◽  
Management Zones ◽  
Apparent Electrical Conductivity ◽  
Specific Management

Peralta, N. R., Costa, J. L., Balzarini, M. and Angelini, H. 2013. Delineation of management zones with measurements of soil apparent electrical conductivity in the southeastern pampas. Can. J. Soil Sci. 93: 205–218. Site-specific management demands the identification of subfield regions with homogeneous characteristics (management zones). However, determination of subfield areas is difficult because of complex correlations and spatial variability of soil properties responsible for variations in crop yields within the field. We evaluated whether apparent electrical conductivity (ECa) is a potential estimator of soil properties, and a tool for the delimitation of homogeneous zones. ECamapping of a total of 647 ha was performed in four sites of Argentinean pampas, with two fields per site composed of several soil series. Soil properties and ECawere analyzed using principal components (PC)–stepwise regression and ANOVA. The PC–stepwise regression showed that clay, soil organic matter (SOM), cation exchange capacity (CEC) and soil gravimetric water content (θg) are key loading factors, for explaining the ECa(R2≥0.50). In contrast, silt, sand, extract electrical conductivity (ECext), pH values and [Formula: see text]-N content were not able to explain the ECa. The ANOVA showed that ECameasurements successfully delimited three homogeneous soil zones associated with spatial distribution of clay, soil moisture, CEC, SOM content and pH. These results suggest that field-scale ECamaps have the potential to design sampling zones to implement site-specific management strategies.

Investigation of dryland salinity using the electrical image method

Soil Research ◽  
1999 ◽  
Vol 37 (4) ◽  
pp. 623 ◽  
Author(s):  
R. I. Acworth
Keyword(s):  
Electrical Conductivity ◽  
Salt Content ◽  
Image Method ◽  
Dryland Salinity ◽  
Conductivity Variation ◽  
South Wales ◽  
Electrical Imaging ◽  
Profile Line ◽  
Conductivity Anomalies ◽  
A Site

Electrical imaging is a 2-dimensional investigation method that can be used to rapidly determine subsurface conductivity variation. In dryland salinity studies, electrical imaging is used to define the vertical extent of high electrical conductivity zones first identified using electromagnetic (EM) profiling equipment. Field techniques are described using 25 or 50 electrodes, connected to a resistance meter by a multi-core cable, to obtain images at a variety of electrode separations. The model of electrical conductivity variation obtained by an inversion of the field data is shown to agree very well with the results of detailed field investigations, including data from soil sampling, 1 : 5 extract analysis, and borehole electrical conductivity logging. Results are described from the Liverpool Plains at Yarramanbah Creek and Round Island, where a thick sequence of smectite clay overlies sands and gravels. The image clearly identifies zones of high salt content in the clay which have been sampled and logged using borehole measurements of electrical conductivity. Results are also described from a dryland salinity area in the upper part of Dicks Creek catchment on the Southern Tablelands of New South Wales. These data show the extent of clay overlying bedrock and correlate very well with the results of 1 : 5 extract analysis from shallow piezometers along the profile line. Electrical imaging is an appropriate follow-up method for the investigation of electrical conductivity anomalies first identified by EM profiling and is advisable before drilling at a site to optimise the location of piezometers.

Redistribution of water following precipitation on previously dry sandy soils

Soil Research ◽  
1975 ◽  
Vol 13 (1) ◽  
pp. 13 ◽  
Author(s):  
BA Carbon
Keyword(s):  
Soil Water ◽  
Seedling Emergence ◽  
Soil Water Potential ◽  
Sandy Soils ◽  
Soil Surface ◽  
Field Capacity ◽  
Wetting Front ◽  
Applied Water ◽  
Dry Soil ◽  
The Relationship

Theoretical and experimental evidence is provided to show that the redistribution of a given amount of water some days after infiltration into a previously dry soil can be predicted, provided that the relationship between soil water potential and soil water content is known. The capillary potential at the wetting front during infiltration into the dry soil is also required. In sandy soils an increase in amount of applied water leads to a decrease in the soil moisture content at the soil surface. This change in 'field capacity' as a function of applied water is shown to strongly influence seedling emergence.

The use of electromagnetic induction to detect the spatial variability of the salt and clay contents of soils

Soil Research ◽  
1987 ◽  
Vol 25 (1) ◽  
pp. 21 ◽  
Author(s):  
BG Williams ◽  
D Hoey
Keyword(s):  
Electrical Conductivity ◽  
Spatial Variability ◽  
Electromagnetic Induction ◽  
New South ◽  
Clay Material ◽  
Soluble Salts ◽  
South Wales ◽  
Apparent Electrical Conductivity ◽  
Highly Correlated ◽  
Land Use Practices

The apparent electrical conductivity (EC,) of a 250 ha area of the Riverine Plain in New South Wales was mapped using a Geonics EM 34/3 electromagnetic terrain conductivity meter. The EC, values obtained were highly correlated with both the total soluble salts and the total <2 km clay material to a depth of 15 m. The spatial variability of both these properties has a direct bearing on present and future land-use practices.

Soil Moisture Deficits in South-Central Sweden

1989 ◽  
Vol 20 (2) ◽  
pp. 109-122 ◽  
Author(s):  
Lotta Andersson
Keyword(s):  
Soil Moisture ◽  
Field Capacity ◽  
Interannual Variations ◽  
Neutron Probe ◽  
South Central ◽  
Normal Ranges ◽  
Moisture Fluxes ◽  
In The Beginning ◽  
Probe Measurements ◽  
Different Parts

Some commonly used assumptions about climatically induced soil moisture fluxes within years and between different parts of a region were challenged with the help of a conceptual soil moisture model. The model was optimised against neutron probe measurements from forest and grassland sites. Five 10 yrs and one 105 yrs long climatic records, from the province of Östergötland, situated in south-central Sweden, were used as driving variables. It was concluded that some of the tested assumptions should not be taken for granted. Among these were the beliefs that interannual variations of soil moisture contents can be neglected in the beginning of the hydrological year and that soils usually are filled up to field capacity after the autumn recharge. The calculated climatic induced dryness was estimated to be rather insensitive to the choice of climatic stations within the region. Monthly ranges of soil moisture deficits (1883-1987) were shown to be skewed and it is therefore recommended to use medians and standard deviations in statistical analyses of “normal” ranges of soil moisture deficits.

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