Fourth Grade NGSS
Biogeology and Heat Generation

Making a mixture of compost and soil and fertilizing the science garden

               Exploring the different between soil and compost
               Using compost to make soil


·         Compost


·         wheelbarrow or bins
small shovels
small rake
Gary the Gardener


any people think compost is soil.   It is not.  Compost is a human way of making nature go faster and creating a product that can add nutrients to the soil to be used by plants.  Compost is great for mixing into the soil when you are planting a new plant. It helps a sandy soil hold moisture and nutrients better and improves clay soils too.

Soil is organic matter plus rocks. The organic matter is from leaves, bark, dead plants, animals, waste of small invertebrates as well as vertebrate.  Other organisms like ants, worms, beetles, and fungi (to name a few) eat on the matter and convert it to humus, which is equivalent to compost.  Rocks are made of minerals (which in turn is composed of elements).  Minerals provide the macro and micro nutrients and they erode into a useable form.

Compost can be created faster and the ingredients can be controlled.  It basically produces carbon and nitrogen.  Nitrogen is an important macronutrients that plants require.  Compost also helps to break up the soil so it can retain water easily. Most compost is not ready for plants to grow because they are missing the important macro and micro nutrients needed for plants.

Rocks are made of minerals.  Minerals are made of elements.  As water passes through rocks, the water starts to break down the minerals to release elements.  It is these elements that are used in the process of supporting larger plants and organisms like worms that basically eat and dissect soil to get nutrients.


Please remember that many children do not do gardening and unfamiliar with tools.  You may want to read “Gary the Gardener” to go over the use of tools. You also might go through the correct use of tools and how to use them effectively with your body.

Go to the following link on tools if you want to take some tools with you to describe there uses.  Tools.

1.    Using compost to enhance soil helps to increase the nutrients.  However, you have to be careful of not adding too much, because it can change the pH of the soil.  Student learn about pH in the fifth grade, so you can tell students that too much of a good thing can be harmful.

2.    Tell students that they are going to make a 1:1 proportion of compost to existing soil.  Hopefully you can find an area where you can dig some up for the students.  Maybe use a coffee plastic tub and have students put one part soil and one part compost in a larger bin or wheelbarrow. 

3.    Mix the mixture with a small shovel.

4.    Find an area either in the garden or around the school yard that you can help put nutrients by adding the new nutrient rich soil. 

Rake the area so it looks good and then water the area.


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