My soils class got off to a good start this week. I found it really interesting so it was easy to pay attention. African violets were also mentioned much to my amusement. It’s nice to be in a class where I’ll actually be able to use what I’m learning. In our first lecture we started to lay the groundwork for the rest of the semester by talking about what plants need from soil, and basic soil structure.
The three things that all plant roots need from soil:
This seems like a pretty obvious requirement, but it is an important one, since the nutrients available for a plant are dependent in a large part on the type of soil a plant is growing in. Nutrients are found on the surface of the soil particles so a soil’s nutrient holding capacity is directly proportional to its surface area.
Plants need water for both respiration and photosynthesis. Water exists in soil as a film around the soil particles. This means that, as with nutrients, a soil’s water holding capacity is directly proportional to its surface area.
While plants are capable of making their own food, they still have to break it down into usable components like we do, which means they need oxygen. They also need to be able to get rid of the carbon dioxide produced by respiration otherwise they will suffer from carbon dioxide toxicity. This means that it is very important for plant roots to have access to air for gas exchange (this is not an issue for the above ground parts of the plant for obvious reasons). Air is found in the space between soil particles.
- (Bonus!) Anchorage
It is important for plants to be able to stand upright. Soil provides a substrate for a plant to anchor its roots in.
So what does this all mean? Well for one, the surface area of a particular soil can have huge impacts on the water and nutrients available for use. This also means that when we water plants too much we can actually suffocate their roots by filling the spaces in the soil with water (instead of air).