In-situ evaluation of internal drainage in layered soils (Tukulu - hessd

Table 1. Summary of the physical and chemical characteristics of the three soil types.
Soil physical properties
Soil forms Tukulu Sepane Swartland
Master Horizons A B1 C A B1 C A B1 C
Coarse sand (%) 5.3 9.2 2.1 5.2 3.5 2.3 4.7 3.2 54.3
Medium sand (%) 9.3 8.8 3.8 10 4.1 2.3 7.6 5.3 4.6
Fine sand (%) 41.2 31 28.3 41.9 41 31 42 37.6 17.2
Very fine sand (%) 25.3 21 8.4 21.5 10.5 18 31.7 26.6 2.5
Coarse silt (%) 2.1 2 3 1 3 1 2 3 3
Fine silt (%) 4.6 2.5 6.5 1 3 1 1 2 3
Clay (%) 11.3 26.4 47.9 19 35 45 11.3 21.9 15
Bulk density (kg m −3 ) 1670 1597 1602 1670 1790 1730 1670 1530 1450
Porosity (%) 34.0 33 32.4 34 33.5 33.8 35 39.9 41.6
K s (mm h −1 ) 36.1 40 9.6 35.2 18.1 1.9 23.5 42.8 76.5
Chemical properties
pH (water) 5.8 6.1 6.5 5.9 6.2 6.3 5.5 5.8 6.8
Ca (c mol c kg −1 ) 35.3 40.8 62.7 30.53 46 50 23 25.78 45
Mg (c mol c kg −1 ) 18.8 20.8 54.7 13.89 21.87 29.76 12.1 13.1 25.4
K (c mol c kg −1 ) 12.8 6.8 12.9 4.63 8.21 7.05 5.5 7.45 7.7
Na (c mol c kg −1 ) 2.4 2.5 3.4 1.96 3.8 3.91 0.7 1.52 2.3
K s = saturated hydraulic conductivity.
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Table 2. θ-h regression functions of soils horizons for the 0–1000 mm suction range.
Soil type Horizons Regression R 2
Tukulu A θ = 0.332–0.00005 h 0.98
B θ = 0.328–0.00004 h 0.96
C θ = 0.324–0.000003 h 0.93
Sepane A θ = 0.327–0.00007 h 0.99
B θ = 0.333–0.00004 h 0.99
C θ = 0.338–0.00004 h 0.99
Swartland A θ = 0.339–0.00008 h 0.99
B θ = 0.347–0.00006 h 0.99
C θ = 0.345–0.00013 h 0.97
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