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Air Encapsulation: I. Measurement in a Field Soil

1986; Wiley; Volume: 50; Issue: 3 Linguagem: Inglês

10.2136/sssaj1986.03615995005000030005x

1435-0661

M.J. Fayer, Daniel Hillel,

Soil Moisture and Remote Sensing

Abstract Encapsulated air is an important component of shallow water table fluctuations. Our objective was to measure the quantity and persistence of encapsulated air in a field setting. Using sprinkling rates of either 3.5 × 10 −6 or 3.8 × 10 −5 m s −1 , we brought the water table in a field soil from a depth of 1.5 m to the surface on several occasions. Moisture contents during and after sprinkling were monitored with a neutron probe. Twice following sprinkling, the water table was maintained at the surface for more than 20 d, during which time we continued to monitor moisture contents. With the water table at the surface, differences between the porosity and the measured moisture content were attributed to encapsulated air. Encapsulated air contents ranged from 1.1 to 6.3% of the bulk soil volume, depending on the rate of sprinkling, soil depth, and initial soil moisture content. During ponding, encapsulated air persisted at the 0.3m depth for up to 28 d. The results indicate that encapsulated air is measurable in a field situation and that its quantity and persistence should be considered in analyzing the results of similar field experiments.