If you’re thinking about here are some questions to first ask yourself (and anyone else who looks remotely interested) about your backyard soil:
- Is the soil worked easily?
- Is the soil full of living organisms?
- Are earthworms abundant in the soil?
- Is water and air available for plant growth?
- Does my garden make me look good?
“I’m really, really mystified by homeowners who will plop down $30,000 to a landscape designer who will come up with a plant palette without ever thinking to take a spoonful of soil to test it first,” says Professor Stephen Andrews, soil scientist at UC Berkeley. “One of the criteria for selecting a landscape architect is to give them a soil quiz! Ask them what kind of soil test they will be providing. Be an informed consumer.”
So, after you’re done hating your compacted soil and admiring yourself in front of the mirror in your new garden hat, it’s time to get scientific. Why? Because we compost- spinning tree huggers believe all home gardeners caring for a plot of land, large or small, can be become superb stewards of their gift from Mother Nature by learning a little soil science.
“If you’re going to do any type of landscaping project, make sure to test your soil first to understand what kind of a baseline you have,” says Andrews. “If you’re changing a large backyard area, doing drainage work or you’ve just purchased a new home, go get a ‘commercial’ soil test done. It may cost you a few hundred dollars, but you’ll have a thorough analysis and interpretation of your land. The soil scientists at the testing company will give you specific advice on how to proceed.”
For the rest of us, who don’t have the green to spend on the brown, it’s perfectly fine to take the mom-and-pop route. Head down to your local plant nursery and purchase a home garden test kit. A good soil test will run about $20.
Andrews recommends Mosser Lee’s Soil Master kit “because of the educational information included. It’s also a simple test. It’s color-coated and it’s idiot-proof, I promise. Do it with the kids or grandkids. Or, get the entire neighborhood and have a soil testing barbecue! One test kit will have enough tubes to do 10 soil tests. You may be the diva who does everything organic, but…you’re living next to Charlie Chevron who uses every petrochemical on the planet. Get together and literally talk dirt.”
With the home soil test, you’ll be testing your soil’s pH. The pH level will tell you if nutrients are actually available to your plants or if you’re just out fertilizing, polluting and wasting your hard-earned cash on garden products.
“The ideal pH of soil for many common plants is 6.5. The reason we want the soil to be slightly acidic is because the plant nutrients are carried in a solution. If it’s slightly acidic, the nutrients can dissolve and can be transported,” says Andrews. “If the pH is too alkaline, the nutrients will sit there like lead balls of pasta, not going anywhere. By having it slightly acidic you have the best pH for nutrient uptake. To lower the pH, use coffee grounds, tea bags, sulfur, aged animal manure or compost. To raise the pH, add limestone or oyster or egg shells.”
Home tests also check the availability of your soil’s macronutrients: nitrogen (N), phosphorus (P) and potassium (K). These are the main nutrients and minerals needed by your plants (which is why you’ll see the letters NPK on fertilizer containers). Once you know which nutrients are already hanging out in your soil, you won’t be wasting money on unnecessary products.
When collecting your home soil sample, choose a few different sections of your yard. For instance, your edible garden in raised beds would be one test area while your front lawn, a slope or a woody spot would each be a separate area to test.
“For each chosen area, do a representative sampling. Pick ten to fifteen different spots in that area and dig down 6-8 in.,” recommends Andrews. “Remove critters, rocks, roots and plant material. You just want soil parts. Take all samples from that area and mix them into a plastic baggie. Label the bag and the area accordingly. For a lawn, dig down only 2-3 in..”
If you’ve decided to do the commercial test, you’ll want to decide just how comprehensive a test you need. Andrews suggests testing for pH nutrient availability, particle size analysis, bulk density, moisture content, organic matter content, macro- and micronutrients and soluble salts. If you live in an urban area and are growing edibles, or in an older home where lead contamination from paint is prevalent, heavy metals testing should be done as well.
As mentioned above, commercial soil testing should be done when you first move into a home. It should also be done every ten years or so, depending on your budget and your gardening success or utter failure.
The home soil test, on the other hand, would be useful to do any time a considerable amount of plants in your yard look beaten down, chewed up or super sluggish. Gardeners don’t have patience for lollygagging plants. Testing your soil twice a year—once in the spring and again in the fall—is especially helpful if you’re growing fruits and vegetables year round.
“Cold season crops have different needs than warm season crops. Like us, our underground soil friends slow down when it’s colder outside,” says Andrews. “The bacteria slow down; but, once the soil warms up, the disco lights come on and they’re ready to party!”