Friday, August 7, 2015

Dishing Up Dirt - Simple DIY Garden Soil Analysis and Testing



Our new old garden has been both loved and neglected over its many years of cultivation. When we arrived, many of the plans were dead or on the brink of dying.  With a lot of hard work (and a little specialist help felling and chipping trees in our urban boundaries), we cleared things back to a healthy skeleton and set about a year-long effort of nurturing the soil to be ready for planting the following winter/spring (now in our hemisphere).  We DIYed our soil testing - here are some of the basic DIY ways to check your own soil.


Soil Structure

Dig a clean-sided hole approximately 30cm deep and look at the soil structure.
  • If your soil is mostly subsoil or fill then you will need to consider augmenting/replacing soil or using raised beds. This is a common issue around new building constructions.
  • If there is a reddish-brown borderline running under your topsoil, this is called hardpan or ouklip. It is a layer of deposited material and/or compacted soil, and will need to be broken up as part of prepping your soil to ensure that water and fine roots can work their way through the ground.
  • If you have good looking workable topsoil, great!

Soil Type

Squeeze and roll a damp handful of soil in your hand. If it forms a solid sausage-like shape and holds form when you touch it, the soil is clay. If it is gritty and crumbly, it is sandy. If it holds but then  quickly crumbles to the touch, then you have loam. You can supplement this check by dropping your handful of soil into a glass or jar and mixing thoroughly, then leaving it to settle for an hour or so.  Stones and sand will quickly settle, fine particles like clay and silt cloud the water and will take a long time to settle, and organic materials will often float.

Soil pH

You can easily test your soil pH with an inexpensive kit (litmus style testing) or tester from your local garden center or online. I opted for a tester (as per the photo above) which allows me to quickly and easily test multiple locations of the garden periodically.  Knowing the pH allows you to either select plants for your soil type or adjust the soil to suit your plants. I was surprised to discover that we have neutral soil - in our area, most soils are slightly acidic. Our used coffee grounds having been making their way to our acid loving plants ever since, but we will need to make some additional pH adjustment provisions for our big old camellias and the new berry patch.


Signs of Life

Take a look around you garden for signs of life.  This might require channeling you inner child (or get the kids to help!) as most ground insects prefer dark areas.  Look under leaf-litter, stones, etc or dig a small shallow hole, and ensure that you have a thriving insect community. The creepy crawlies, along with less visible fungi and bacteria,  help to break down organic reside, reduce the risk of pets and disease, and make nutrients available to your plants.  You can also (unless you are in a very hot dry area) do a quick earth work check by digging up a shovelful of soil and looking through it for worms - a healthy worm population is a sign that your soil has good organic matter on which to feed.

Drainage

Before you fill that hole, make sure its around 30cm deep and 15cm wide, and then fill it with water. Allow it to drain and rest overnight to ensure that the soil isn't unusually thirsty when you do your test. The next day, refill it with water and measure the rate of drainage on an hourly basis. Drainage of around 5cm/hr is ideal.  If your hole drains very rapidly or very slowly, you may want to make adjustments to the soil or planting selection, or build a raised bed.

Absorption

In our garden, we had the additional problem of having some water-repellent (hydrophobic) areas.  Adding clay and/or soil wetters were not suitable for our soil-type and location, so we instead set about the long slow process of using a crop-cover and working to increase microbial activity. I will share a post about crop covers sometime soon.

We didn't need to do an absorbency test - our problem was readily apparent.  Water (rain or applied) on our problem areas would simply bead on the soil's surface, roll around in little dirt coated droplets to the lowest point, and then sit.  Not good at all!  If you are concerned about your soil's absorption, you can observe how long it takes a water drop to absorb.
  • If it immediately absorbs (less than 1 second), great! 
  • If it takes less than a minute, you soil is still absorbing moisture at a reasonable rate.
  • If it takes over a minute, then consider working to improve your soil's absorbency.  
  • If it still hasn't absorbed after a few minutes, consider treating for hydrophobia. 

Note: In some locations, particularly (but not limited to) older sites or long-established areas, soil may carry trace contamination from old metal roofing, lead paints, and any number of legacy factors. If this is your situation, as a precautionary measure, you may want to research additional testing options in your local area before planting an in-ground edible garden.

No comments:

Post a Comment

Thanks ever so much for taking the time to leave us a comment - we read each and every one. We appreciate you taking the time to say hello and share your thoughts.