Implications of surfactant application on soil hydrology, macronutrients, and organic carbon fractions: An integrative field study

This study investigates the effects of repeated applications of the non-ionic soil surfactant H2Flo (ICL-SF Inc., Israel) on the soil water content, hydraulic conductivity, nutrient distribution, and organic carbon fractions (OCFs) in non-hydrophobic loamy sand soils under subsurface drip irrigation. Our results indicate that H2Flo treatment reduces both saturated and unsaturated hydraulic conductivity while promoting the uniform irrigation distribution, consistent with previous findings on surfactants’ effects on sandy soils. An increase in soil pH levels, organic carbon content, and extractable magnesium, calcium, and potassium was observed in treated soils, with elevated levels of potassium permanganate oxidizable organic carbon (POXC) implying accelerated decomposition rates. Notably, a positive linear relationship was found between POXC and the increased NO₃^–-N content of treated soils, suggesting induced conditions of nitrification. However, the carbon fractions water-soluble organic carbon (C_ws) and hot water-soluble organic carbon (C_hws) remained quantitatively unchanged, even though they exhibited a positive linear relationship with the soil’s hydraulic conductivity. The study highlights the crucial role of monitoring changes in OCFs and nutrient dynamics after surfactant application to optimize soil organic matter utilization and chemical fertilizer management.