We love to focus on what is growing above the ground, but it’s what’s below it that can make all the difference. What on earth is so important about dirt?
Dig down into it and you’ll find soil is actually a complex food web with many different interwoven life forms all working together to create a rich source of growing medium for our planet. Bacteria, algae, insects, lichens, nematodes and all sorts of things with odd names are just part of the underground world in which the seeds and roots of our plants thrive. Or not.
When our plants or lawns are not lush, flourishing or producing at their potential, we can look to the soil for some answers. If you do it before the growing season starts, you can positively affect your lawn or garden’s productivity, and possibly your budget.
It could be that your soil does not hold the combination of nutrients that what you’re growing needs – but how do you know for sure if you don’t test it? The organic matter (dead organisms and their parts) in soil is like a bank. That bank stores currency (energy and nutrients) that help its “customers” (our plants) prosper. One of the most valuable but easy things you could do right now for your garden or lawn is to test the soil to see what kind of “currency” it holds, or lacks.
What is a soil test, anyway?
A soil test is an examination of a dirt sample to measure the content of elements (calcium, copper, manganese, magnesium, phosphorus, potassium, sodium, sulfur and zinc). The quality of nutrients available for plants determines how much fertilizer your soil needs. Soil pH and acidity tests can be done, too, to determine if and how much lime (calcium) is needed to maintain the right pH level.
There are all kinds of soil testing. More detailed, expensive tests can be done to determine if metals like lead are present. But basic soil testing is all the average gardener like you and me need to do. And, it’s one of the easiest.
Why do a soil test?
What happens in the soil is like an underground chemistry lab. Stuff is happening and affecting other things. For example, if you have applied too much lime, soil pH rises higher than needed and that causes nutrients like boron, copper, iron, manganese and zinc to become less available to plants.
Ends guess work. When you have a test done, you have specifics. You know how much fertilizer or lime your soil needs and you don’t have to guess.
Evaluates nutrients. It’s helpful to know what you’re working with so you know what you’re putting your plants into, and if it has what they need or not.
Encourages plant growth. When you know what amendments your soil needs, you can concoct the best soil for optimal growth of your lawn or garden and improve the odds of your plants doing better.
Elevates environmentally-conscious practices. Some experts say homeowners use more agricultural chemicals than farmers. Runoff from lawns and gardens is now as great a water pollution problem as farms and industry. We can help keep water and streams clean by not over feeding our gardens or adding lime to lawns that don’t need it.
Economizes expenditures. Instead of buying supplies for the soil that we may or may not need, education about our soil helps us purchase only what we need in the quantities needed. It also helps us increase the odds of successful growth, minimizing wasting money on poorly growing plants.
How do I do it?
Timing – The best time is now, early spring. You need a few months before you start new planting. Lime especially needs time to affect pH levels. You can also test in late fall. If you’ve recently fertilized or limed, wait six to eight week before sampling. For established lawns and landscape, test once every three to four years.
Tools – Clean tools are important. Make sure your hands are clean or gloved, that your extraction tools and containers are clean. Don’t touch the sample with your hands. Collect your sample with a soil probe, auger, spade, garden trowel or shovel, and don’t use brass, bronze or galvanized tools because they contaminate samples with copper or zinc.
Test Areas – Soil composition can vary, so make sure you sample areas separately and don’t mix the soil or assume your lawn will have the same soil content as your garden. For each area, you can take several samples and combine them. If you notice an unhealthy spot in your lawn but the rest looks good, take two different samples.
Take Core Sample – Be sure to follow the instructions of whatever testing method you select. Generally you’ll need a cup to two cups of soil per sample area. General depth guidelines are:
Lawns – 3-4” deep
Vegetable and flower gardens – 4-8”
Shrubs – 4-6” around base
Be sure to remove any mulch. Break up the soil with the tool or your gloved hand to separate and dry the soil naturally, and remove any rocks or non-soil material. Soil cannot be wet.
Texture Analysis – Though not a part of the chemical testing, texture tells a story, too. Squeeze some soil in your hand and open it. If the soil falls apart when you poke it, your soil contains excess sand. If it holds together, roll it into a line and gently bend it. If it doesn’t break past a 1-inch section, it contains too much clay.
Local Extension Office, Private Lab or Lawn Care Service – . Local agricultural extension offices offer the most accurate, precise tests for the least amount of money – $2 to $20 for basic soil testing. Additional tests for texture and metals are separate and cost more.
Commercial labs are also an option, depending on the details of testing. Some lawn care services also provide soil testing services. Both of these tend to be more costly than the extension offices, and are more for large areas requiring major investments.
Buy a Home Soil Analysis Kit – . Soil test kits are available at garden centers and online. A home soil test will give you immediate analysis of your soil’s pH, and some also determine nitrogen, phosphorous and potash. Kits run from $7 to $20. They are not always known to be consistent or as accurate as extension testing.
Conduct Home-made Test – . You can feel like a kid in chemistry again and do your own pH test. It’s the simplest, cheapest option, but won’t give you numbers. All you need is vinegar and baking soda. Put some soil into a container. Add half-cup of vinegar. If the soil bubbles or fizzes, you have alkaline soil. Amend it with sulfur or pine needles. If the soil does nothing, scoop another sample into another container. Add half-cup of water and stir. Then add half-cup of baking soda. If the soil bubbles or fizzes, you have acidic soil. Amend it with wood ash or lime.
A pH primer
Soil is either acidic (sour) or basic (sweet) and this is measured by pH, which directly affects the availability of nutrients. In the U.S., the Northeast and Midwest tend to be acidic; soil west of the Mississippi and in Florida tends to be alkaline.
pH is measured on a scale from 0 to 14, 7 being neutral. Anything less than 7 is acidic, anything greater than 7 is basic.
With proper pH levels, your fertilizer works better. The benefit of a precise test from an extension office is that you know exactly how much fertilizer or lime you would need to add.
Low pH – Low levels of pH mean metals like aluminum, copper, lead and iron get higher. The fix for low pH is to apply lime. Lime raises the soil pH and provides calcium and magnesium. Lawns need lime if pH falls below 6. It should be applied now (late winter, early spring). The type of soil you have (silt, clay, loam or sand) affects how much you apply so be sure to check the instructions. Lime doesn’t move within the soil, so it must be worked in so maximum contact is made. It also comes in a range of textures from very finely ground to pelleted. The finer the texture, the faster it affects pH.
Neutral pH – Most nutrients offer the best availability at pH near 6.5. Vegetables, turf gra
sses, flowers and shrubs generally prefer a neutral soil (6.1-6.9). Most lawns do best between 6.5 and 7.
High pH – With high levels of pH, plants may suffer from a deficiency of nutrients and lowered nitrogen transformation. When pH rises above 6.5, trace elements become less available (iron, copper, zinc, manganese). Some plants require an acidic soil to flourish (Azaleas, rhododendrons, blueberries and conifers).
Soil really is more important than seed. If you see a lush, green lawn, you can bet that homeowner has done some research on the soil underneath. Testing your soil now takes minimal effort but offers great potential for results. Go do a little digging, and see what you discover!