The effect of a surfactant (H2flo) in irrigation water on hydrophobic soils
Results
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In the WDPT it was found that after applying H2Flo and drying the soil at 60ºC, the hydrophobic soil turned into hydrophilic soil. However, a gradual decline in H2Flo effectivity was observed with time (Fig.4).
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200 ml irrigation water were dripped over the Shafdan and control sands. First irrigation was with tap-fresh water; second irrigation with H2Flo water; and third irrigation with tap water after partial drying of the H2Flo wet soil. In the dune sand there is an improvement in respect to soil wetting after applying the H2Flo. In the Shafdan sand (hydrophobic) there is a decrease in hydrophobicity and the water flow is more continuous compare to the no-treated conditions (Fig. 6.1-3).
Highlights
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Cultivated soils are rich in organic matter. Consequently, they are becoming hydrophobic and as a result, the following processes are being negatively affected: water infiltration; nutrients and contaminants transport; soil erosion; agricultural water management and more.
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This study examines the hypothesis that adding of surfactant (H2Flo) to irrigation water will help to minimize hydrophobicity of sandy soils rich in organic matter.
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Tested soils were collected from the Shafdan recharge ponds (hydrophobic) and from adjacent Sand dune (control).
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The methods that were used are : Water Drop penetration test (WDPT) (Fig.1), Darcy’s test (Fig.2) and flow experiments in Hele-Shaw cells (Fig.3).
Fig.1: Water Drop penetration test (DPT)
Fig.2: Hydraulic conductivity test
Fig.3: hele Shaw cell experiments
Fig.5: Hydraulic conductivity values for Shafdan and control sands with and without H2Flo.
Fig.4: Comparison between soil treated with H2Flo and control 1, 3, and 7 days after applying of the surfactant
Fig.6.1: Hele-Shaw irrigated with fresh water.
Fig.6.2: Hele-Shaw irrigated with H2Flo.
Fig.6.3: Hele-Shaw irrigated with fresh water after drying of the H2Flo treated soil.
Discussion
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Research findings did not support hypothesis as minor impact of H2Flo was observed for the hydrophobic conditions.
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Nevertheless, a significant improvement of soil wetting was observed for the “simple” sand dune after applying the H2Flo.
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This is surprising as the added surfactant is reducing , theoretically, the capillary suction of the pores in the soil.
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Could be that the impact of the surfactant on the liquid surface tension (sigma) and the contact angle with the soil (theta) leads to a net increase in capillary suction (h).
