scholarly journals When measuring soil water content, field practices affect neutron moisture meter accuracy

1993 ◽  
Vol 47 (6) ◽  
pp. 29-31 ◽  
Author(s):  
Blaine Hanson ◽  
Gylan L. Dickey
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Moisture Meter ◽  
Neutron Moisture

Screening potato clones for resistance to common scab (Streptomyces scabies) in the field

1972 ◽  
Vol 79 (1) ◽  
pp. 75-81 ◽  
Author(s):  
F. A. Langton
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Common Scab ◽  
Severe Infection ◽  
Field Capacity ◽  
Streptomyces Scabies ◽  
Screening Tests ◽  
Moisture Meter ◽  
Neutron Moisture

SUMMARYPotato varieties were grown in the field in soil uniformly infected with Streptomyces scabies. In 1969 tubers were severely and evenly infected but in 1971 infection was slight and not uniform. Agreement of varietal ranking with agricultural experience was good in 1969 but poor in 1971.In 1971, plots protected from rainfall after planting were dry enough at the start of tubering for severe infection; covering the plots for a further 6 weeks followed by irrigation to field capacity resulted in good yields of evenly and severely scabbed tubers. Irrigation during this period suppressed scabbing. The results were easily interpreted in relation to fluctuations in soil-water content measured by a neutron moisture-meter.The efficiency of using only one site and the need to reduce variability in scab screening tests are discussed.

Neutron moisture meter : the dependence of their response on soil parameters

Soil Research ◽  
1986 ◽  
Vol 24 (1) ◽  
pp. 11 ◽  
Author(s):  
DJ Wilson ◽  
AIM Ritchie
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Nuclear Reactor ◽  
Diffusion Theory ◽  
Soil Parameters ◽  
Moisture Meter ◽  
Neutron Moisture ◽  
Theory Calculation ◽  
Neutron Absorption Cross Section

A multigroup diffusion theory calculation based on a nuclear reactor neutronics code is used to determine the response of a neutron moisture meter to changes in soil parameters such as dry soil density, soil water content, thermal neutron absorption cross-section and neutron scattering crosssection. Empirical equations which fit the results can be used to estimate the response at values of the soil parameters other than those used in the calculations. These equations can also be used to estimate the accuracy with which the parameters must be known to achieve a required accuracy in the derived soil water content.

A field comparison of three neutron moisture meters

1993 ◽  
Vol 33 (1) ◽  
pp. 59 ◽  
Author(s):  
GJ O'Leary ◽  
M Incerti
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Sandy Loam ◽  
Soil Types ◽  
Separate Variable ◽  
Counting Time ◽  
Comparable Performance ◽  
Neutron Moisture ◽  
Use Studies

A study was undertaken to compare 3 neutron moisture meters (NMMs) over a range of counting times on 2 soil types in north-westem Victoria. The meters were a Pitman Wallingford 225 (WAL225), a Campbell Pacific Nuclear 503 (CPN503), and a Campbell Pacific Nuclear 501DR (CPN501). The soil types were a grey self-mulching clay and a solonised brown soil (sandy loam). The 3 NMMs exhibited different count rates in water, from 242 to 2645 counts per second. It was necessary to increase the counting time of CPN501 to 64 s to achieve a comparable performance to WAL225 at 16 s. Over the 15-month experiment, standard counts remained relatively constant for WAL225 and CPN501, but CPN503 showed pronounced variation. In field calibrations, the inclusion of depth (as a separate variable to account for neutron absorbing gradients in the soil profile) made significant improvement to the regression of all NMMs irrespective of counting time. No improvements in the calibration were achieved using density corrections from core samples for individual layers. On both soil types, WAL225 and CPN503 performed similarly to each other, with very similar residual mean squares and coefficients of determination. On the grey clay, WAL225 and CPN503 explained 77 and 88% of the variation in soil water content, respectively. CPN501 performed poorly, even with a 64 s counting time, and explained only 52% of the variation when depth was included. When depth was excluded this fell to 25%. On the sandy loam, WAL225 and CPN503 explained 76 and 74%, respectively, of the variation in soil water content. CPN501 again performed poorly with a 64 s counting time, accounting for 65% of the variation when depth was included and 33% with depth excluded. Examples of poor calibrations or none at all in water use studies are discussed and typical errors are demonstrated.

Selection and use of representative sites in a large neutron moisture meter network

Soil Research ◽  
1979 ◽  
Vol 17 (2) ◽  
pp. 249 ◽  
Author(s):  
GG Johns
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Root Mean Square ◽  
Mean Square ◽  
Short Term ◽  
Moisture Meter ◽  
Routine Basis ◽  
Neutron Moisture ◽  
Key Sites ◽  
The Relationship

The assessment of the representivity of individual sites in a large neutron moisture meter (NMM) network, and the errors incurred by selecting subsets of various sizes, and using different methods to estimate the full set value from the subsets, is described. Soil water data collected over 13 months from the NMM network (240 sites, divided into eight strata) were analysed to determine the relationship between individual sites and their stratum means. Relationships were assessed using the following four methods: (1) root mean square of the discrepancy; (2) linear regression; (3) quadratic regression; (4) power curve regression. Sites best related to their stratum means were then included in various size subsets, and estimates based on these subsets were compared with the respective full stratum means using 24 months' data. The best estimates of stratum means were obtained by using quadratic regressions and c. eight sites per subset. Using this method, the root mean square discrepancy between estimates of profile water content and observed full stratum means averaged 2.1 mm when the total profile was estimated directly and 2.5 mm when the profile water content was computed as the sum of individual estimates for four arbitrary horizons within the profile. Daily readings of one group of selected subsets indicated the potential of frequent NMM readings at key sites to indicate short-term changes in the soil water content of an area. The performance of the selected subsets has been monitored for a further 12 months as an independent check on their representivity. The root mean square discrepancy of estimates during that period was 2.7 mm. Subsequently only the selected eight sites in each stratum of the field study are being read on a routine basis.

Components of variance involved in estimating soil water content and water content change using a neutron moisture meter

Soil Research ◽  
1979 ◽  
Vol 17 (2) ◽  
pp. 237 ◽  
Author(s):  
DF Sinclair ◽  
J Williams
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Total Variance ◽  
Calibration Error ◽  
Location Error ◽  
Instrument Error ◽  
Moisture Meter ◽  
Site Heterogeneity ◽  
Neutron Moisture ◽  
The Mean

In order to rationalize the allocation of resources in the estimation of soil water content using the neutron moisture meter, it is essential to have a thorough understanding of the sources and magnitudes of the variance components. An error analysis, taking into consideration current technology and methodology, identifies three components of total variance, attributable to: location error due to site heterogeneity with respect to soil water and random error associated with positioning the probe; calibration error; and instrument error. Data from three locations illustrate that the location variance is the major source of random error in the total variance of an individual estimate. For the total variance of the mean over a site containing n sample estimates, the large location component is reduced by a factor of n such that in many circumstances it will reduce to the same order as the calibration component which is independent of n. This is particularly true for field calibration. The instrument error and that error introduced by the use of count rate ratio are small and contribute in a very minor way to the total variance of the mean. The analysis reveals that the nature of the relationship between the magnitude of the location error and the calibration error is dependent on site heterogeneity, the value of n and the precision of the calibration equation.

Factory-Calibrated Soil Water Sensor Performance Using Multiple Installation Orientations and Depths

2020 ◽  
Vol 36 (1) ◽  
pp. 39-54
Author(s):  
Gary W. Marek ◽  
Thomas H. Marek ◽  
Kevin R. Heflin ◽  
Dana O. Porter ◽  
Jerry E. Moorhead ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Irrigation Management ◽  
Soil Water Potential ◽  
Water Storage ◽  
Clay Loam ◽  
Clay Loam Soil ◽  
Neutron Moisture ◽  
Loam Soil

Abstract. The use of soil water sensors is commonly advocated to aid and improve irrigation management in crop production systems. However, there are concerns about how sensor type, installation technique, sensor orientation, and soil texture may affect sensor accuracy. A field study was conducted to compare the performance of three commercially available soil water sensors (Acclima 315L, Decagon GS1, and Campbell Scientific 655) and a soil water potential sensor (Watermark 200SS) using different installation orientations of horizontal insertion, laid horizontal placement, and vertical insertion at depths of 15, 46, and 76 cm (6, 18, and 30 in.) in an irrigated clay loam soil field. Results indicated all sensors demonstrated similar trends of soil water content in response to wetting events (precipitation and irrigation) at the 15 cm depth following a 4-month settling period prior from the start of the growing season. Comparatively, the Acclima 315L performed well using horizontal insertion compared to calibrated neutron moisture meters (NMMs) at depths of 46 and 76 cm with R2 of 0.73 and 0.96 and slopes of 1.36 and 1.47, respectively. In addition, water storage in the 0.9 m soil profile integrated using the horizontally inserted Acclima 315L across the three depths matched closely with profile water storage determined by the NMMs with a mean difference (MD) and root mean square error (RMSE) of 25.7 and 36.4 mm. However, site-specific corrections or calibrations for each sensor type are required for accurate soil water content estimations with this clay loam soil for irrigation management applications. Keywords: Corn, Irrigation management, Neutron moisture meter, Soil water content, Soil water sensors, Semi-arid region.

scholarly journals Comparison of neutron moisture gauges with nonnuclear methods to measure field soil water status

1992 ◽  
Vol 49 (spe) ◽  
pp. 111-121 ◽  
Author(s):  
C. Kirda ◽  
K. Reichardt
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Spatial Dependence ◽  
Water Status ◽  
Field Soil ◽  
Soil Water Status ◽  
Neutron Moisture ◽  
Level Of Significance ◽  
Space Dependence

The neutron moisture gauge is compared with the gravimetric-core soil sampling technique, tensiometers and resistance blocks in relation to stability, Held variability, spatial dependence and number of samples needed at a given level of significance. The variance of field water content measurements with neutron moisture gauges is lower than that of the gravimetric sampling, which therefore requires 2 to 6 times as many samples as the number of measuring sites of the gauges to attain the same level of significance. The space dependence of the measurements made with the subsurface gauge varied depending on the average field soil water content. No space dependence was evident when the water content was lower than 0.2 cm³.cm-3 (50% saturation). Measurements with the tensiometers and resistance blocks manifested no spatial dependence and therefore randomly selected measuring sites can be adapted to Held research work where these methods are to be utilized. Soil water content measurements estimated with neutron moisture gauges showed well defined temporal stability (i.e., the lowest, average and the highest soil water content measurements occur at the same field site) which implies that soil water status of an entire field can be assessed with measurements limited to few locations. Measurements with both tensiometers and the resistance blocks are time variant (i.e., the site giving field average water content changes spatially in time) owing to their relatively smaller measuring domains (i.e., scale of the area which can be represented by a single measurement) as compared to neutron gauges. Therefore it is not possible to define the measuring sites of the tensiometers and resistance blocks as to assess soil water status of the entire field, as it could be done with the neutron gauge.

SOIL WATER CONTENT AFFECTS THE AVAILABILITY OF PHOSPHATE

1985 ◽  
pp. 185-189
Author(s):  
M.C.H.Mouat Pieter Nes
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Solution ◽  
Equivalent Reduction

Reduction in water content of a soil increased the concentration of ammonium and nitrate in solution, but had no effect on the concentration of phosphate. The corresponding reduction in the quantity of phosphate in solution caused an equivalent reduction in the response of ryegrass to applied phosphate. Keywords: soil solution, soil water content, phosphate, ryegrass, nutrition.

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