Knowing your soil composition is very important if you are attempting to amend your existing soil to get your premium soil for growing. You soil is made up of four components; sand, silt, clay, and organic material.
Sand has the largest particle size of all these components and creates large gaps between them which is excellent for water to flow through and roots to grow in. On the contrast it is terrible for retaining water and will dry out quickly.
Silt has medium size particles and if you had to choose a single component for effective growing this would be it. Its particles are large enough to allow healthy root growth and also retains water. Though some plants like their roots to be a little more on the drier side so in isolation this may not work for all plants
Clay has the smallest particles thus making it very difficult for water to flow through it. Not really much positive to say about this stuff though if your goal is to hold water this property can be great when used as a substructure out of your plants normal growing area 1-2 feet down, think of it as a natural earth box.
Organic Material is the good stuff (leaves, compost, grass clipping) the stuff that makes your “dirt” alive and becoming living soil. This feed beneficial bacteria and worms to provide rich vermicompost to add natural nutrients to your garden.
Now we know what we are looking for, lets find out what we have in our back yard. All of my vegetable gardens are raised which consist of soil I have brought in myself so I know they will be very loamy and high in organic matter to makes things more interesting.
1. Get Dirt: I dug a small hole (about 6 inches deep in a dead part of my lawn. I filled an apple juice container about 2/3 full. Any container can work for this as long as it is clear and uniform in shape/volume (width/depth) at the bottom.
2. Add Water and Shake: Fill with water about 1-2 inches from the top and shake for at least one minute to ensure particles are well mixed
3. Let Soil Components Rest: Set on a flat surface until water on top is clear or 24 hours (whichever comes first)
4. Do the Math: After the dust particles have settled you should see 3 distinct lines and possibly some stuff floating in the water. The sediments will settle according to their particle size (sand, silt, clay) and organic material should float above the water.
Given the knowledge mentioned above we can now calculate the percentage of each soil component to determine our soil type take a couple simple measurements.
Total Soil Height = Measure from the bottom of the container to top of sand/silt/clay
Sand Height = Measure from bottom of container to top of sand
Silt Height = Measure from top of sand to top of silt
Clay Height = Measure from top of silt to top of clay
% Sand = Sand Height / Total Soil Height X 100
% Silt = Silt Height / Total Soil Height X 100
% Clay = Clay Height / Total Soil Height X 100
Example of math using my Data
69.47% Sand = 66mm / 95mm X 100%
29.47% Silt = 28mm / 95mm X 100%
1.05% Clay = 1mm / 95mm X 100%
Tip: You can measure with cm/mm/inches and the formulas will still work out as long as you use the same units for all measurements
Now using your Sand/Silt/Clay percentages you can now use the triangle diagram below to determine your soil type. Though it can vary depending on the types of plants you are growing (i.e. succulents like the sand) but in general a nice “Silty loam” is what you want to shoot for, so if you are lacking adding some organic matter is the best way to get moving in that direction
Using my data I have “Sandy Loam” soil, though if I would have dug a few inches deeper I would have had a much higher percentage of clay. Even if you are sure you know what your soil type I recommend trying this out you might end up surprised.
This site was practically started because of my oldest daughters science fair project Why Don’t Strawberries Grow in the Wintertime? Now with my youngest in kindergarten she was very excited to have a science fair project of her own, which should be pretty obvious from the picture above.
With no influence from me she decided on answering the question if smaller seeds will sprout faster. These days science fairs are more than just gluing some some Styrofoam balls to a couple hangers and calling it good. They require using true scientific methods and procedures, which is pretty advanced for a 5 year old, although she didn’t seem to notice. Here is the contents of her experiment…
Hypothesis: Smaller seeds will grow bigger in a shorter amount of time because their roots don’t need to grow as big to support the plant
Procedure: I planted 3 seeds of each plant type (lettuce, cilantro, pumpkin) and watered them and gave them sunlight and I watched them grow.
Results: I planted the seeds at the same time and measured the growth over 2 weeks. The lettuce was the first one to sprout. The cilantro was the next one to sprout and the pumpkin was the last one to sprout. At week one, the lettuce was still the largest, cilantro was the second, and the pumpkin was the smallest
Conclusion: Smaller seeds sprouted and grow quicker than larger seeds.
I was very impressed with her project as well as the hypothesis, one of those moments of thinking, “hmm…is that how actually works…” Though you probably can think of a few plants that would break the hypothesis but pretty much on target for most plants.