Soil structure and drainage

Fri. Mar. 30, 2018

Click below to listen to my 2 min. Garden Bite radio show:  Soil structure and drainage

This is a perennial topic!!

If you peruse descriptions of a particular plants needs, they almost all say, prefers “well-drained soil”.  What is that?   It’s well structured soil.  That is soil that contains enough pores, the gaps between soil particles, to allow air and water to flow freely.  Ideally, the sand, silt and clay particles are arranged so they occupy only half of the space, leaving the other half as pore space.  A 50/50 split is primo.   More in-depth information on Soil Structure.

Soil types

Now, most of us don’t have that in our yards.  Our soils are more clay or more sand or compacted.  One of the reasons we add compost is to fluff up the soil, which is the same thing as trying to get to that 50/50 split.

Soil type jar testing

One effective way to combat poor soil is to build raised beds and use a good soil.  I suggest checking out Creekside Soils.

Adding blend of compost and soil
Adding blend of compost and soil

An easy way to gauge the drainage of your soil is to dig a square hole about 1 foot deep and wide, fill it with water and allow it to drain completely.  Immediately refill the hole with water and place a ruler in it to measure the water’s depth.  After 15 minutes, measure how much the water has fallen; multiply this by 4 to calculate how much the water will drain in one hour.  An hourly drop of less than an inch indicates poor drainage.  In well-drained soil, the drop in water level will be 1 to 6 inches per hour.  Soils that drain  more than 6 inches per hour are considered dry.

More resources:

Cornell University Soil Basics

Colorado State University Extension ‘Correcting drainage problems’

soil percolation test

soil percolation test