Because so many of the nutrients that plants rely on are water-soluble, there is a tendency for some to leach away into the sub-surface groundwater.

Understanding how this groundwater leaching works is important for growers because it affects the availability of a number of nutrients in our soils and acts as a nutrient outflow frow the ecosystem which must be accounted for.

Let's look at what groundwater leaching is and how exactly this process unfolds.

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What Is Groundwater Leaching?

When more water is present in an ecosystem than is lost to evapotranspiration and surface runoff, that water needs someplace to go.

Acted upon by gravity, it permeates down through the soil layers, finding its way to subsoil and eventually to parent material and bedrock.

Pro Tip:

Head over to our article on Soil Layers for a quick refresher on how soil and mineral layers stack.

Groundwater leaching is one component of the larger hydrologic cycle that plays out in ecosystems, so head on over to our Hydrologic Cycle article to understand the other ways that water circulates.

Because water is such an effective solvent, dissolving quite a few nutrients and minerals into solution, this percolation down into sub-surface layers can carry away nutrients in the process.

As nutrients descend to the sub-soil and below, they fall out of reach of all but the most deep-rooted plants.

Trickling down even lower, into parent material and eventually bedrock, the nutrients will become completely inaccessible to all plants.

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This is bad news for your plants if you're not aware of the process and don't know how te replace the nutrients that are leached away into the groundwater.

Which Nutrients Are Prone to Groundwater Leaching?

Typically the more soluble a given nutrient is in water, the more prone to groundwater leaching it is.

The following is a list of all the water-soluble nutrients that plants need which can be leached away into groundwater, sorted from most-prone-to-leach to least-prone-to-leach:

  1. Nitrate (NO₃⁻)
  2. Chloride (Cl⁻)
  3. Sulfate (SO₄²⁻)
  4. Boron (B)
  5. Magnesium (Mg²⁺)
  6. Calcium (Ca²⁺)
  7. Potassium (K⁺)
  8. Molybdenum (Mo)

What Climates Are Most Susceptible to Groundwater Leaching?

Wet climates that receive heavy rainfall, and climates with wet seasons or monsoons that bring significant rainfall over short periods of time - these are the most-suscoptible to more severe leaching.

What Soil Types Are Most Susceptible to Groundwater Leaching

  • Sandy and rocky soils drain at higher rates than silty or clay soils, making them generally more prone to leaching - assuming that they are not suffering from compaction and that they are not located in climates with high rates of evapotranspiration.

    What Can Gardeners Do to Reduce Nutrient Leaching?

    What Can Gardeners Do to Replace Nutrients Lost to Leaching?


    • That's all for now, thanks for reading!

    If you have any questions, comments, or would like to connect with fellow gardeners, head on over to the forum and post there.