After seven years of gardening in my current spot, four years of blogging about it, and two years with the Master Gardeners, I'm just now getting around to getting my soil tested. Why now? Truth be told, my veggie garden wasn't very productive this year at all. The only crops that produced anything of substance were chard, cantaloupes and Juliet tomatoes. Cucumbers, corn, beans, squash, garlic, potatoes, sweet potatoes and big tomatoes were all a bust.
There's lots of factors to consider when a veggie garden doesn't produce well, including but not limited to soil fertility, the variety of vegetables planted, timing and spacing of crops, pesticide contamination and irrigation. A soil test can help sort out some of the fertility issues, but not all. We can't test soil for microbial diversity, for example.
Nitrogen (N), phosphorus (P) and potassium (K), the three major macronutrients in soil, are what most of us think about when we think about fertilizing our veggies and ornamentals. You'll see N-P-K listed as percentages on labels of commercial fertilizers (10-10-10, 8-2-4). But there's more to soil fertility than just N-P-K. Micronutrient content, salinity, structure, texture, soil biology and pH all play important roles, too, among other things. It's complicated!
Though a soil test won't answer all my questions, it should give me some clues as to what might be going on, and at the very least, end the guessing game of what nutrient might or might not be missing. So, I've decided to test two types of soil in my garden: the soil in the back yard that's been untouched for about a decade (possibly more) and the soil in the veggie garden beds that I've amended numerous times. (Not sure why I wrote "Lawn" on that first bag -- it's mostly weeds and horseherb back there!)
To collect the samples, I carefully dug out ten divots of soil from each area, at least six inches down, after scraping the live plant matter off the top. I mixed the divots together in a clean bucket and removed any visible rocks, weeds, roots, and mulch before bagging the samples.
What's striking to me is how similar the two dry soil samples look. The unamended soil on the left is a little stickier (due to a higher clay content and less organic matter) and a little grayer in color. Otherwise, I can hardly tell the difference from the amended soil on the right.
However, when wet, the difference is clear. The unamended soil (this time on the right) has the texture of modeling clay, while the amended soil (on the left) is soft and crumbly.
Clearly I've improved the soil structure and texture by adding store-bought garden soil, compost, manure, and mulch to my beds once or twice a year for the past seven years. But what about the rest? Time to find out.
More to follow...stay tuned!
Words and photos © 2009-2013 Caroline Homer for "The Shovel-Ready Garden". Unauthorized reproduction is prohibited.