Jar Test


Soil Analysis


Garden-Tip 1068

Gardening Tips for successful and beautiful Landscapes and Gardens


Good Soil is vital to the health of your plants!


All soil is generally comprised of particles that fall into three groups. The smallest is clay, then silt and the largest is sand. Clay compared to sand is as small as a baseball is to the White House. Clay tends to drain very slowly while sand drains too fast. Good “soil” has a mixture of these that will allow for adequate oxygen throughout, but also retain water long enough to prevent plant drought. This is why “silt” is so nice, as a medium sized particle it has the best of both worlds. 40 % sand, 40 % silt and 20% clay makes a nice loamy soil.




If you would like to know what percent these particles comprise your soil, try doing a Jar Test.


Put enough dirt from your planting area in a quart size jar so that the level of the jar is about 2/3 full. Then add water until nearly full and shake.

Let settle for a couple hours. Use a ruler to measure the height of each soil layer.


Organic matter (like compost) will float, and the percent of compost can’t be measured with the jar test. It can however, be measured by a soil laboratory. A bit complicated and expensive. Organic material is nearly non-existent in our desert soil. Trust me!

The sand will settle to the bottom while the silt and clay will settle on top of that. Measure the depth of each & calculate the percentage. In this example we have approximately 7% clay, 20% silt and 73% sand. This is a “sandy loam” and will exhibit excellent mostly rapid drainage. Not a common soil here.


To use our ON-LINE calculator to analyze your jar test measurements and what this might mean for your landscape click here: è , or visit your local Star Nursery and ask our plant specialists. Soil characteristics directly affect proper watering and fertilization.