Neutron probe measurement of soil water content close to soil surface

Falleiros, M.C.; Sanchez, Andrea; Souza, M. D. de; Bacchi, Osny Oliveira Santos; Pilotto, J.E.; Reichardt, Klaus

doi:10.1590/s0103-90161993000300002

Cited by 6 publications

(5 citation statements)

References 4 publications

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“…2): the first from 0-70cm and the second from 70-200 cm. However, neutron losses in the atmosphere near the surface necessitated a separate calibration for the portion up to 20 cm (Evett and Steiner, 1995;Falleiros et al, 1993). Three straight calibration curves corresponding to respective soil layers were determined for each site (Table 1).…”

Section: Resultsmentioning

confidence: 99%

Transfer of moisture through the unsaturated zone in the tropical forest using the neutron probe

Fouepe

Kengni

Rao

et al. 2009

Int. J. Environ. Sci. Technol.

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ABSTRACT:Knowledge of moisture content is crucial in assessing spatial and temporal movement of water through the unsaturated zone. Moisture storage is also important for monitoring the soil water balance and for validation of water balance models. The purpose of this work was to determine and analyse moisture content profiles at point locations in the unsaturated zone of a lateritic soil around Nsimi, south of Cameroon. Neutron probe has been connected to a set of tensiometers in an area of 60 ha. A comparative study between a site covered with vegetation and a site uncovered was conducted to assess the influence of vegetation in the process of moisture transfers. The results showed that the spatial distribution of moisture profiles varied according to the site and the texture of the soil, with in general increasing of moisture from the surface horizon toward the deeper layers. The mean values of moisture varied from θ m = 0,397 cm 3 /cm 3 on barren site, against θ m = 0,429 cm 3 /cm 3 in vegetation. Values of suction were generally strong in surface and at depth, but weak in the intermediate layers.

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Section: Resultsmentioning

confidence: 99%

Transfer of moisture through the unsaturated zone in the tropical forest using the neutron probe

Fouepe

Kengni

Rao

et al. 2009

Int. J. Environ. Sci. Technol.

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“…Alternatively, many direct methods are available, such those that make use of electrical resistivity (Umeda, 1969), neutron moderation (Falleiros et al, 1993), gamma ray densitometry (Gurr, 1962) and dielectric capacitance (Uno, 1970;Topp et al, 1990). Some of the dielectric-based methods which use empirically calibrated relationships between volumetric water content and sensor output signal include time domain re‰ectometry (Nissen et al, 1998), amplitude domain re‰ectometry (Nakajima et al, 1998) and frequency domain re‰ecto-metry (Lukangu et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Measurement of Degree of Saturation on Model Ground by Digital Image Processing

Yoshimoto

Orense

Tanabe

et al. 2011

Soils and Foundations

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The degree of saturation of ground is conventionally measured at discrete points using transducers, soil moisture sensors, etc. In this paper, a novel method was developed to directly measure the degree of saturation of continuous region of ground by noting the variation in color of the ground as the amount of moisture in the soil changes. In this research, a series of experiments was conducted for the purpose of developing a method to measure the degree of saturation of ground by digital image processing. From photo images taken at various soil moisture contents, the colors of the images were converted into numerical values which were then related to known degrees of saturation. The results of the experiments showed that a method to measure the degree of saturation of ground by image processing was possible. The relation between degree of saturation and luminance value can be expressed in terms of second degree function. Good results were obtained for two soil samples with diŠerent colors and grain size distributions. The margin of error was in the order of ±5z. The method was validated through vertical seepage tests, where good agreements were obtained between the measured degrees of saturation by tensiometers and those estimated from the proposed method. The method illustrates the possibility of measuring the degree of saturation of a larger portion of the ground, which is di‹cult to perform using conventional procedures. With this method, contour diagrams of degree of saturation can be produced, making it possible to visualize the propagation of the saturated region.

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“…The neutron probe was calibrated at the same site (Falleiros et al, 1993) and yields data of soil water content θ on a volume basis, i.e., m 3 H 2 O m -3 soil, so that the variability of θ includes the variability of soil bulk density.…”

Section: Methodsmentioning

confidence: 99%

Soil spatial variability and the estimation of the irrigation water depth

Reichardt

Silva

Bassoi

et al. 2001

Sci. agric. (Piracicaba, Braz.)

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The effects of soil water spatial variability previous to irrigation and of the field capacity on the estimation of irrigation water depth are evaluated. The experiment consisted of a common bean (Phaseolus vulgaris L.) crop established on a Kandiudalfic Eutrudox of Piracicaba, SP, Brazil, irrigated by central pivot, in which soil water contents were evaluated with a depth neutron gauge, in a grid of 20x4 points with lag of 0.5 m. In a given situation, the 80 calculated irrigation water depths presented a coefficient of variation of 29.3%, with an average water value of 18 mm, maximum of 41mm and minimum of 9 mm. It is concluded that the only practical way of irrigation is the use of an average water depth, due to the inherent variability of the soil, and that the search for better field capacity values does not imply in better water depth estimates.

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Neutron probe measurement of soil water content close to soil surface

Cited by 6 publications

References 4 publications

Transfer of moisture through the unsaturated zone in the tropical forest using the neutron probe

Transfer of moisture through the unsaturated zone in the tropical forest using the neutron probe

Measurement of Degree of Saturation on Model Ground by Digital Image Processing

Soil spatial variability and the estimation of the irrigation water depth

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