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  • Find out how students can make silage at school.

    You will need (per student group)

    • A large plastic drain pipe, approximately 40-50 cm in length and 15 cm in diameter
    • Plastic sheeting and duct tape
    • A 14-15 cm disk with a rubber seal so that it that fits snugly into the drain pipe
    • Weights
    • Lots of freshly cut grass


    Seal one end of the drain pipe with the plastic sheeting and duct tape. Make sure that it is well-sealed to keep all air out.

    • Fill the pipe with cut grass, pressing down of the top to push out as much air as possible.
    • Place the disk as a lid on top of the grass and compress the grass more to squeeze out any remaining air. Important: the lid must fit very snugly to keep air out of the pipe.
    • Use weights on top of the disk lid to compact the grass. The lid should drop slightly as the grass ferments.
    • Fermentation could be finished anywhere from 2 weeks to about 45 days.


    The optimum moisture content of your fresh grass is 60-70%. You can test this by taking a clump of grass and tightly squeezing it into a small ball in your hand, then letting your hand open up. Ideally, no water will come out of the ball when you squeeze, and when you open your hand the ball will slowly fall apart. If water comes out when you are squeezing the grass, the grass is too wet (the moisture content will be over 75%) and it must be allowed to dry a bit more.

    If the ball falls apart immediately when you open your hand, it is too dry and some water should be added.

    Good fermentation has taken place if the silage smells fresh and fruity, and is yellow-brown or green. Silage is bad if it smells rotten or has any black, slimy parts.

    Factors to vary

    Students can try different variations to see the effect they have on the silage - especially which variations make good versus bad silage:

    • Grass/pasture type
    • Amount of grass in the pipe
    • Moisture content (What happens if the grass is too wet? Too dry?)
    • Time of fermentation before opening the pipe
    • Leaving the pipe top open to the air (This will allow fungal and other bacterial growth, resulting in compost rather than silage).

    Related content

    See the related unit plan and case study.

      Published 20 November 2007 Referencing Hub articles
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