A couple weeks ago, I attended a lecture on soil testing sponsored by Clallam County’s Master Gardeners. Practically speaking, soil tests assist growers and gardeners by directing us toward treating and augmenting soils to suit our growing needs. Soil pH affects helpful bacteria and fungi and influences whether essential minerals are available to plants. This is critical info!
I learned that our Northern Olympic Peninsula’s soil tends to run acidic or close to a low pH of 5.5, in part due to the amount of moisture that permeates the earth here each year. Acid soil is on the opposite end of the spectrum from the higher pH alkaline soil, and happiest soil measures roughly 6.5 -7 as shown on this nifty scale by Australian Government’s “Caring for Our Country”:
One thing of importance to note: Although a difference of just .5 may not seem like much, the pH scale is logarithmic, which means a pH of 7.0 is actually ten times more acidic than a pH of 8.0.
I learned how to take an accurate soil sample just in time for the first homework assignment of a class I begin tomorrow, training me to be a community gardening volunteer a.k.a. Master Gardener. So in today’s sunshine I put the lesson into practice and dug 12 holes in my barren veggie garden. The flat area I decided to sample lies in the middle of the wonderful raised beds and is the area we grow potatoes, squash, beans, and more.
Extraction of samples meant digging six inches deep (12 times) in a zig zag pattern through the veggie garden and taking a true slice of that six inches so that the top and bottom of the slice are included in equal proportions. An alternative is to borrow a soil probe from a local county’s conservation district office or to purchase a probe.
All slices went into a large bucket which I then stirred and extracted three cups of soil from. The sample is in a baggie in my fridge until tomorrow’s class. We will be submitting our samples to be analyzed at a lab in Oregon and then reviewing results in one of the upcoming classes. In addition to exploring soil pH and the percentage of organic matter, we’ll interpret mineral results for Nitrogen, Phosphate, Potassium, Magnesium, Calcium, and Sodium.
That’s some dirty homework.