Calibration and Field Testing of a Two‐probe Gamma Gauge

Rawitz, E.; Etkin, H.; Hazan, A.

doi:10.2136/sssaj1982.03615995004600030004x

Cited by 16 publications

(7 citation statements)

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“…Equation [3] in Rawitz et al (1982) was used to calculate bulk density using an unattenuated count rate (J 316000) and mass attenuation coefficients suggested by them for soil and water. Parallel Al access tubes 0.30 m apart were used to take measurements.…”

Section: Methodsmentioning

confidence: 99%

Bulk Density of a Sandy Loam: Traffic, Tillage, and Irrigation‐Method Effects

Meek¹,

Rechel²,

Carter

et al. 1992

Soil Science Soc of Amer J

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Modern crop production creates a cycle between soil compaction caused by traffic and alleviation of this condition by tillage or natural processes such as freezing and thawing. The objective of this study was to evaluate important management practices as they relate to changes in bulk density of a tilled sandy loam soil. Practices evaluated were irrigation method, time between tillage and traffic, tire pressure and wheel load of applied traffic, and controlled traffic. Relationships among bulk density, penetration resistance, and infiltration rate were determined. Experiments were conducted in the San Joaquin Valley of California, on a sandy loam soil (Entisol) with an organic‐matter content of <1%. After tillage, settling and trafficking of a soil resulted in rapid changes in its bulk density until a new equilibrium was reached. Tire pressure of 408 kPa and wheel weight of 2724 kg applied at moisture contents near field capacity resulted in a bulk density of 1.92 Mg m−3, compared with a value of 1.67 for no traffic. The time interval between tillage and traffic did not affect final bulk density. Drip irrigation, which did not saturate the soil, resulted in a bulk density of ≈0.1 Mg m−3 lower than flood irrigation, which saturated the soil surface. Wheel traffic in the furrow resulted in only small changes in the bulk density within the row. When tillage did not occur between cropping seasons, traffic caused high bulk densities in the furrow but only small changes in the row. An increase in bulk density from 1.7 to 1.89 Mg m−3 decreased the infiltration rate by four times and increased resistance to penetration at the end of the season by three times. Knowledge of how management practices affect bulk density can aid growers in reducing recompaction following tillage.

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Section: Methodsmentioning

confidence: 99%

Bulk Density of a Sandy Loam: Traffic, Tillage, and Irrigation‐Method Effects

Meek¹,

Rechel²,

Carter

et al. 1992

Soil Science Soc of Amer J

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“…Equation [3] presented by Rawitz et al (1982) was used to calculate bulk density using an unattenuated count rate (Jo = 316 000) and mass attenuation coefficients suggested by them for soil and water. Volumetric water content is part of the equation and was measured using a Troxler neutron probe.…”

Section: Plot Establishment and General Proceduresmentioning

confidence: 99%

Infiltration Rate of a Sandy Loam Soil: Effects of Traffic, Tillage, and Plant Roots

Meek

Rechel

Carter

et al. 1992

Soil Science Soc of Amer J

139

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Settling and trafficking of a soil after tillage causes rapid changes in the soil physical condition until a new equilibrium is reached. In the soil studied, a Wasco (coarse-loamy, mixed, nonacid, thermic Typic Torriorthent) sandy loam, soil compaction reduces infiltration rates, which under grower conditions could result in inadequate infiltration of irrigation water to supply crop requirements. Our objective was to evaluate important management practices as they relate to changes in the infiltration rate of a sandy loam soil. Factors evaluated were traffic, tillage between crops, and the formation of channels by roots of perennial crops. Tillage between crops increased the infiltration rate during the first part of the season in trafficked soils but decreased or had no effect on nontrafficked soil. Alfalfa (Medicago sativa L.) increased the infiltration rate fourfold during a 2-yr period in a heavily compacted soil. An increase in bulk density from 1.6 to 1.8 Mg m-3 decreased infiltration rate 54% in the field. Hydraulic conductivity of undisturbed cores was at least seven times larger than that measured in columns of disturbed soil (same bulk density). This difference is believed to be the result of natural channels in the undisturbed soil that are destroyed when the soil is disturbed. Under controlled traffic, when surface seal is not a problem, tillage will not be necessary to obtain adequate infiltration rates except in the wheel paths.

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“…By comparison, other studies have shown that bulk densities measured using a neutron-gamma surface gauge tended to be lower than the conventional ring method (e.g. Timm et al, 2005;Bertuzzi et al, 20 1987;Rawitz et al, 1982), although this difference was not statistically significant.…”

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confidence: 71%

Proximal sensing for soil carbon accounting

England¹,

Rossel²

2018

Preprint

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Abstract. Maintaining or increasing soil organic carbon (C) is important for securing food production, and for mitigating greenhouse gas (GHG) emissions, climate change and land degradation. Some land management practices in cropping, grazing, horticultural and mixed farming systems can be used to increase organic C in soil, but to assess their effectiveness, we need accurate and cost-efficient methods for measuring and monitoring the change. To determine the stock of organic C in soil, one needs measurements of soil organic C concentration, bulk density and gravel content, but using conventional laboratory-based 5 analytical methods is expensive. Our aim here is to review the current state of proximal sensing for the development of new soil C accounting methods for emissions reporting and in emissions reduction schemes. We evaluated sensing techniques in terms of their rapidity, cost, accuracy, safety, readiness and their state of development. The most suitable technique for measuring soil organic C concentrations appears to be vis-NIR spectroscopy and for bulk density active gamma-ray attenuation. Sensors for measuring gravel have not been developed, but an interim solution with rapid wet-sieving and automated measurement appears 10 useful. Field-deployable, multi-sensor systems are needed for cost-efficient soil C accounting. Proximal sensing can be used for soil organic C accounting, but the methods need to be standardised and procedural guidelines need to be developed to ensure proficient measurement and accurate reporting and verification. This is particularly important if the schemes use financial incentives for landholders to adopt management practices to sequester soil organic C. We list and discuss the requirements for the development of new soil C accounting methods that are based on proximal sensing, including requirements for recording, 15 verification and auditing.

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Calibration and Field Testing of a Two‐probe Gamma Gauge

Cited by 16 publications

References 0 publications

Bulk Density of a Sandy Loam: Traffic, Tillage, and Irrigation‐Method Effects

Bulk Density of a Sandy Loam: Traffic, Tillage, and Irrigation‐Method Effects

Infiltration Rate of a Sandy Loam Soil: Effects of Traffic, Tillage, and Plant Roots

Proximal sensing for soil carbon accounting

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