Mass flow refers to nutrients moving ...

• A. In air via diffusion
• B. With water
• C. By osmosis
• D. In solid rock

Answer: (B)

Mass flow is the bulk transport of dissolved nutrients carried by the movement of water through the soil. When water moves—whether from rainfall, irrigation, or plant uptake—the nutrients dissolved in that water are swept along with it. This makes mass flow especially important for nutrients that stay dissolved easily, so they can be moved quickly with infiltrating or flowing water. It differs from moving through air, from even water movement across a membrane (osmosis), and from movement through solid rock, where there isn’t a continuous liquid phase to carry dissolved ions.