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Tension Infiltrometer Measurements

Implications of Pressure Head Offset due to Contact Sand

Agriculture and Agri-Food Canada, Greenhouse and Processing Crops Research Centre, 2585 County Road 20, Harrow, ON, Canada N0R 1G0

View larger version (20K): [in a new window]   Fig. 1. Schematic of the tension infiltrometer (TI) including water supply tube, infiltration disk or plate, contact sand layer, and retaining ring; Tcs and a are the thickness and radius of the contact sand layer, respectively.

View larger version (14K): [in a new window]   Fig. 2. Dependence of pressure head offset on flux density out of the tension infiltrometer, q(h0) (Eq. [6a]); Kcs and Tcs are the field-saturated (rewet) hydraulic conductivity and thickness, respectively, of the contact sand layer.

View larger version (19K): [in a new window]   Fig. 3. Dependence of pressure head offset on the thickness of the contact sand layer (Eq. [6b]). The diamonds are flux density, q(h0), = 0.004 cm s–1 < field-saturated (rewet) hydraulic conductivity of the contact sand layer, Kcs; the squares are q(h0) = 0.016 cm s–1 > Kcs; and the circles are q(h0) = 0.01 cm s–1 = Kcs.

View larger version (16K): [in a new window]   Fig. 4. Dependence of pressure head offset on the field-saturated (rewet) hydraulic conductivity of the contact sand layer, Kcs (Eq. [6c]); q(h0) parameter is the flux density out of the tension infiltrometer and Tcs is the thickness of the contact sand layer.

View larger version (23K): [in a new window]   Fig. 5. Impacts of pressure head offset (h = hs – h0) due to contact sand on tension infiltrometer (TI) calculations of: (a) near-saturated hydraulic conductivity, K(h); (b) sorptive number, *(h); (c) flow-weighted mean pore diameter, D(h); and (d) number of flow-weighted mean pores per unit area, N(h). Plots using soil surface pressure head, hs, are corrected for offset, while plots using TI membrane pressure head, h0, are not.