Dual Field Calibration of Capacitance and Neutron Soil Water Sensors in a Shrinking-Swelling Clay Soil

Fares, Ali; Buss, Peter; Dalton, Melinda S.; El‐Kadi, Aly I.; Parsons, Lawrence R.

doi:10.2113/3.4.1390

Cited by 20 publications

(32 citation statements)

References 23 publications

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“…Several authors (Tardif, 2003; Geesing et al , 2004; Blonquist et al , 2005; Czarnomski et al , 2005; Yashikawa and Overduin, 2005; Campbell, 2006; Cobos, 2007) note that site‐specific soil moisture sensor calibration improves θ v measurements substantially. More accurate soil moisture measurements can therefore be achieved using site‐specific calibration by relating an equation between the actual θ v (achieved by the oven‐drying method) and the sensor voltage output (Tardif, 2003; Fares et al , 2004). To this end, soil samples were collected from a section of a south‐facing hillslope of 8°, which had adjacent grass and P. incana and inter‐patch bare areas.…”

Section: Methodsmentioning

confidence: 99%

The hydrological response of Pteronia incana‐ invaded areas in the Eastern Cape Province, South Africa

Odindi

Kakembo

2010

Ecohydrology

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The impact of vegetation invasion on hillslope soil moisture dynamics was investigated by comparing three surface cover conditions. Soil moisture variations under grass, bare areas and Pteronia incana, a patchy invader shrub, were monitored fortnightly between 01 November 2007 and 01 May 2008 in an experimental setup where high frequency ECH 2 O EC-20 soil moisture probes connected to a 5-channel Em50 datalogger were calibrated and installed in the field. Grass cover had consistently high moisture readings during the three major rainfall episodes identified. Soil moisture retention was also greatest under grass cover. The difference in post-rainfall moisture retention between grass and P. incana surfaces was significant up to about 6 days; thereafter, a parallel trend in soil moisture change was noted. Grass cover experienced the highest moisture loss after each rainfall episode. The constrained soil moisture budget under P. incana and bare areas has implications for runoff conditions and landscape functionality. Despite this, P. incana's resource capture capability, as demonstrated by persistent, albeit limited soil moisture retention, must be taken cognizance of when developing strategies to rehabilitate rangelands with P. incana-bare surface mosaics.

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Section: Methodsmentioning

confidence: 99%

The hydrological response of Pteronia incana‐ invaded areas in the Eastern Cape Province, South Africa

Odindi

Kakembo

2010

Ecohydrology

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“…The gravimetric SMC readings were converted into volumetric units by multiplying them by bulk density values. Clay soils change their volume with changes in water content (Murray and Quirk 1980) leading to an increase in bulk density when the clay soil gets drier (Fares et al 2004) and vice verse. Thus, the bulk density value at each gravimetric SMC measurement was determined by measuring the bulk density at wilting point and at field capacity.…”

Section: Methodsmentioning

confidence: 99%

The impact of various sprinkler irrigation patterns on spatial soil moisture variation in Vertisols

Al-Kufaishi¹,

Sands

Andersen

2008

Precision Agric

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The objective of this research was to assess the effect of soil cracks on soil moisture distribution under various sprinkler irrigation applications and to identify the optimal irrigation strategy that enhances soil moisture distribution and reduces water drainage for the upper soil layer 0-250 mm. The assessment was made for six irrigation events: the first two were for 10 and 46 mm water applications using a hand shift-set sprinkler system. The second set was for 43 and 19 mm water applications using the lateral move system with fixed sprayer heads and the third pair of events were for 43 and 32 mm water applications using the lateral move system with rotating sprinklers. The experiments were conducted on two adjacent fields at the University of Queensland, Gatton, Australia. Each field was divided into 2 m 9 2 m grids that covered 62 sampling locations. For each event, the initial soil moisture content (SMC) was measured at each sampling location before irrigation. After irrigation, catch can readings were recorded for each sampling location. After 12 h overnight, the second set of soil moisture measurements was taken at each location. The area1 distribution of SMC for the studied applications was quantified. An attempt was made to identify the relationship between the applied water uniformity using catch cans and the soil moisture uniformity using gravimetric water content measurements. The study also took into consideration variables that could affect the soil physical and hydrological properties including the field slope, the soil texture, the infiltration rate, the salt content and the soil organic matter content of the two fields. Since the soils were cracking clay Vertisols, further analyses were conducted on the crack dynamics, size and distribution using image analysis techniques. The research findings demonstrated that the cracks were the main contributors to water drainage below 250 mm soil depth due to the micro-run off from the crust surface to the cracks. The cracks ranged from a few millimeters to more than 40 mm in width. It was observed that the cracks which were wider than 15 mm remained open after irrigation for the specified application rates. Improving the irrigation system application uniformity did not always result in higher uniformity of the surface SMC (0-250 mm). The event that best enhanced soil moisture distribution and thus improved soil moisture recharging was observed after the sixth irrigation event when the field received 32 mm water application. The soil was at a relatively high initial SMC of 25%, (which represented 43.3% of the plant available water range) and the sprinkler water uniformity was rather high above 87% Christiansen coefficient of uniformity (CUc). At this SMC, the extent of soil cracking is limited.

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“…, 1993). This would result in a 3.6% reduction in NP count compared to no‐air gap (Fares et al. , 2004).…”

Section: Methodsmentioning

confidence: 99%

“…Accurate measurement of SWC is becoming important in recent years due to the increasing demand and competition for water between agricultural, domestic and industrial water (Evett et al. , 2002; Fares et al. , 2004), especially in the water‐scarce areas such as Syria.…”

Section: Introductionmentioning

confidence: 99%

Comparison of nuclear and capacitance‐based soil water measuring techniques in salt‐affected soils

Al-Ain

Attar

Hussein

et al. 2009

Soil Use and Management

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A field calibration experiment was carried out on salt‐affected clayey soil in Syria, to compare the sensitivity to soil electrical conductivity (ECe), and bulk density (ρb) of two instruments for estimating soil moisture: the neutron probe (NP) and the Diviner 2000 capacitance probe (CP). The results showed that the values of the correlation coefficient of the calibration were decreased when the ECe and ρb values increased; this decrease was more pronounced for the Diviner 2000, indicating that it was more sensitive to ρb and ECe than the NP. When only scaled frequency was used in the fitted equation, the Diviner 2000 in wet soil underestimated soil water content significantly at all depths, but especially in the top layer, by up to 0.09 cm3/cm3 compared with gravimetric determinations. However, in dry soil, the Diviner 2000 overestimated the volumetric water content by up to 0.05 cm3/cm3 in the top 15 cm, and by 0.03 cm3/cm3 at 30‐45 cm depth. The performance of the neutron probe was better overall; using a factory calibration curve no significant differences were observed between NP estimates and the gravimetric values. Including both ρb and ECe in the calibration equations improved the fits, although the regression coefficient (R2) for the Diviner 2000 remained low.

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Dual Field Calibration of Capacitance and Neutron Soil Water Sensors in a Shrinking-Swelling Clay Soil

Cited by 20 publications

References 23 publications

The hydrological response of Pteronia incana‐ invaded areas in the Eastern Cape Province, South Africa

The hydrological response of Pteronia incana‐ invaded areas in the Eastern Cape Province, South Africa

The impact of various sprinkler irrigation patterns on spatial soil moisture variation in Vertisols

Comparison of nuclear and capacitance‐based soil water measuring techniques in salt‐affected soils

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