A surfactant is a substance that reduces the surface tension of water, allowing it to spread more evenly across surfaces such as leaves or soil. It works by having both water-attracting (hydrophilic) and water-repelling (hydrophobic) parts, which disrupt the natural cohesion of water droplets.
In gardening, surfactants are commonly added to sprays like pesticides, foliar fertilizers, or neem oil to improve coverage and contact. This helps solutions coat leaf surfaces more uniformly, increasing effectiveness and reducing runoff. Some wetting agents used in potting mixes are also surfactants, helping dry soil absorb water more readily instead of repelling it.
Surfactants vary in type, including nonionic (most common for plants), anionic, and cationic, with nonionic forms generally being safest for plant tissues.
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