MadSci Network: Botany |
Plants get several things from soil to help them grow. Soil anchors the plant in one place. Soil is the source of water and minerals for almost all plants. It is also important that the plants be able to get air to their roots through the soil.
This brings us to what makes a good soil. Soil is composed of (1) broken up rocks and (2) dead organisms (organic matter). The broken up rocks are in very small pieces but of different sizes. There are large pieces (sand), middle-size pieces (silt), and small pieces (clay). Sand is good to have in soil because it drains well and provides air spaces for the plant roots to get air. Clay is good to have because it holds on to minerals and water. All sand and the roots may dry out. All clay and the water may not even be able to get to the roots. For most plants, good soil contains some of each type of particle.
Organic matter is mostly the remains of plants that used to be living in the soil. In natural systems, the nutrients from these dead organisms are recycled to the new organisms by decomposing in the soil. In cultivation of a lawn or crop or flowers where the plant material is not allowed to return to the soil, these nutrients must be replaced by fertilizer of some kind. Composting lawn waste and using it in a garden is one way of doing this.
For some good information and easy experiments to do on your own soil go try the page on Virtual Garden-Soil Facts.
Try the links in the MadSci Library for more information on Botany.