Fertilisers, Leaching and Eutrophication · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

When fertiliser reaches the river

Science · Organisms & Life Processes · ages 15-16
Name ______________________   Date ____________

  1. What is an algal bloom?

    • Fish gathering to spawn
    • Algae multiplying fast on extra nitrate, clouding the water
    • Rocks dissolving in rivers

  2. Why can rain steal nitrate from a field?

    • Nitrate dissolves easily in water
    • Nitrate floats into the air
    • Rain carries tractors away

  3. Oxygen in the water crashes while the algae are growing. Is that right?

    Circle one:   True   False

  4. Nitrate has just reached the river in sunlight. What comes next?

    • An algal bloom
    • Instant fish death
    • Cleaner water

  5. What strips the oxygen after the bloom dies?

    • The green colour itself
    • Decomposers breathing as they decay the dead algae
    • Sunlight evaporating the river

  6. Which change cuts leaching, and what does it cost?

    • Spreading before storms, costing nothing
    • Buffer strips beside streams, costing set-aside land
    • Doubling every dose, costing less

  7. A farmer doubles the dose before a storm to be safe. What is wrong with the plan?

    • Storms fix nitrogen for free
    • Crops absorb double with no loss
    • Surplus washes off, so testing, splitting, and timing beat doubling

  8. A field a mile from any river still kills fish downstream. How?

    • Wind blows fish upstream
    • Field drains carry leached nitrate sideways into streams
    • Fertiliser teleports
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Answer key

For grown-ups. Fold this page away before handing over the rest.

When fertiliser reaches the river W1-mt_9lTF20DWOZ-s1

  1. Algae multiplying fast on extra nitrate, clouding the water · Extra nitrate is still plant food, so algae use it to explode in number.
  2. Nitrate dissolves easily in water · The same solubility that feeds roots lets surplus wash into drains.
  3. False · Growing algae release oxygen; the fall comes when decomposers decay the dead bloom.
  4. An algal bloom · Sunlight plus nitrate lets algae multiply before anything else happens.
  5. Decomposers breathing as they decay the dead algae · Dead algae rain down as food, and decomposer breathing spends the oxygen fish need.
  6. Buffer strips beside streams, costing set-aside land · Strips catch runoff, and the price is land kept out of crops.
  7. Surplus washes off, so testing, splitting, and timing beat doubling · Skill means matching dose and timing to what plants will actually use.
  8. Field drains carry leached nitrate sideways into streams · Drainage connects distant fields to rivers through leaching.
Worksheet · LightMySky