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    • Rights: University of Waikato
    Published 30 July 2013 Referencing Hub media
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    Water can leave the land through a process called leaching1, and this is where the water moves directly down through the soil profile and into groundwater2.

    And that’s probably the largest way that nitrogen3 will leave a farm is when you have got water in excess of what is a called the field capacity of the soil at that site, which is the amount of water that a soil can normally hold without leaching – basically, water starting to move down though it.

    As that water moves, it can carry different chemicals4 with it as well and in particular carries negatively charged chemicals with it. Positively charged chemicals are held by the soil because soil is slightly negatively charged. One of the important forms of nitrogen is called nitrate5, and that is negatively charged and so is repelled by soil, and you get that moving down with the water to groundwater and then onto surface waters6 like streams.

    Acknowledgement
    Professor Louis Schipper, University of Waikato

    1. leaching: When a compound becomes dissolved in water and moves from one place to another, for example, a fertiliser in the soil dissolves in rain water and ends up in a stream.
    2. groundwater: Water located beneath the Earth’s surface in soil spaces and in fractures of rocks.
    3. nitrogen: A non-metal – symbol N, atomic number 7. Nitrogen is essential for life. It is a component of many molecules that make up cells, including DNA and proteins.
    4. chemicals: Everything is made up of chemicals. All matter (anything made of atoms) can be called chemicals. They can be in any form – liquid, solid or gas. Chemicals can be a pure substance or a mixture.
    5. nitrate: A chemical composed of three oxygen atoms for every nitrogen atom.
    6. surface water: A body of water above the substrate or soil surface – for example, streams, rivers, lakes and oceans.

    Appears in

    INTERACTIVE

    The terrestrial nitrogen cycle

    An interactive showing the main components of the terrestrial nitrogen cycle. Select one of the buttons to find out more.

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      leaching

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      2. When a compound becomes dissolved in water and moves from one place to another, for example, a fertiliser in the soil dissolves in rain water and ends up in a stream.

      chemicals

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      3. Everything is made up of chemicals. All matter (anything made of atoms) can be called chemicals. They can be in any form – liquid, solid or gas. Chemicals can be a pure substance or a mixture.

      groundwater

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      4. Water located beneath the Earth’s surface in soil spaces and in fractures of rocks.

      nitrate

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      5. A chemical composed of three oxygen atoms for every nitrogen atom.

      nitrogen

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      6. A non-metal – symbol N, atomic number 7. Nitrogen is essential for life. It is a component of many molecules that make up cells, including DNA and proteins.

      surface water

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      7. A body of water above the substrate or soil surface – for example, streams, rivers, lakes and oceans.

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