Soil Tests.

The soil is the great connector of our lives, the source and destination of all.
~ Wendell Berry, The Unsettling of America, 1977

We have had the ground beneath us our entire lives, yet until a person begins gardening, she may know little about it. One of the most exciting things about gardening is learning about the soil, taking care of it, working it, and seeing it improve for the effort.

Where a chef tastes his soup to see what's needed to spice it up (Bam!), a gardener needs to perform a soil test to take her garden to the next level. A soil test is a definitive way of understanding your soil—its structure, nutrient content, pH, and potential contaminants (heavy metals, chemicals) present. Soil tests will identify any problems and also the solutions (which are usually cocktails of soil amendments). Most amendments may not be necessary if you are enriching your garden soil with compost, rotating your crops, and allowing beds to lay fallow for a season. But if soil amendments are necessary, follow directions carefully, and aim for moderation and balance. Always remember, although you may want high yields and healthy vegetables, your ultimate aim should be for healthy soil. You are part of an ecosystem, sharing the soil with millions of soil creatures and microorganisms that can benefit or be harmed by your actions. As long as you keep soil health as your goal, the entire garden ecosystem will be healthy and thrive.



STRUCTURE

Soil structure (granular, platy, blocky, columnar, or prismatic; and structureless— single grained or massive) relates to how the soil particles are arranged in its natural state (before you dig it up). This website offers drawings and photographs to help identify soil structures. Many things impact soil structure, such as soil texture (clay-silt-sand ratios), drainage, and compaction. A soil rich in compost or other organic matter has excellent soil structure (granular–loose & crumbly). Good soil structure improves soil aeration, reduces runoff, and encourages healthy root development, all of which increase plant health and harvest yields. Working the soil while it is wet can be very damaging to its soil structure. It's best to work the soil when it is neither wet nor dry.



NUTRIENT CONTENT

The three main garden nutrients are Nitrogen, Phosphorus and Potassium. When purchasing fertilizers, often you will see numbers within parentheses such as (13-1-0). This can be read as the amounts of (Nitrogen-Phosphorus-Potassium).

(N) Nitrogen present in the soil is converted to nitrate (NO3-) and ammonium (NH4+) by nitrogen fixing bacteria. Plants feed on nitrate and ammonium to establish healthy stem and leaf growth. Nitrogen is also used in the decomposition process. Wood needs a lot of nitrogen to decompose, so if your plants are slow growing, they may be competing for nitrogen with wood present in the soil or mulch. Spent coffee grinds and blood meal are excellent sources of nitrogen, and if necessary should be applied in the Spring. Crops of green manure (nitrogen fixing plants such as alfalfa, beans, clover, peas, peanuts) can be rotated with other crops; after harvest, just use a spade fork to turn the decaying plants back into the soil.

(P) Phosphorus stimulates root growth and flower and seed production. But be careful not to overdo it. Too much phosphorus can lead to other nutrient deficiencies, plus phosphorus can easily become a pollutant, contaminating rivers and streams through rain runoff. Generally there is enough phosphorus present in home garden soils, so it is not usually necessary to amend the soil with phosphorus fertilizers. However, if your soil test reveals a phosphorus deficiency, bone meal and aged animal manures are rich sources of it.

(K) Potassium aids in photosynthesis and the absorption of water, and is essential for a plant's overall health and immune system. Good sources of potassium include seaweed kelp, liquid seaweed, wood ash, dried aged animal manures, and rock potash (for the seriously potassium deficient soil).

Major Trace Elements or Macronutrients include (S) Sulfur, (Ca) Calcium, and (Mg) Magnesium.

(S) Sulfur helps plants to build proteins. It also lowers soil pH, correcting alkalinity and boosting acidity. Sulfur is useful for acid-loving crops such as beans, blueberries, cantaloupe, corn, garlic, lettuces, okra, onions, parsley, peppers, potatoes, squash, sunflowers, watermelon, and also non-edible plants such as evergreens and rhododendrons. If you keep hydrangeas, adding sulfur to the soil will turn the blossoms blue. Good sources of sulfur include leaf mould, sawdust, pine needles and bark.

(Ca) Calcium is essential for proper cell growth. It also raises soil pH, correcting acidity and boosting alkalinity. Adding crushed eggshells (be sure to rinse them with dish soap and warm water) or crushed seashells will help add calcium to your soil. Tomatoes like calcium because it prevents blossom end rot. You can sprinkle crushed eggshells or seashells around broccoli, cabbage, peppers, and tomatoes to prevent pest damage caused by cabbage worms, cutworms, and slugs. If you have a prevalence of these pests, you should have a soil test done to test for calcium deficiency. Soil amendments that boost calcium include: limestone (calcium carbonate - CaCO3), gypsum, bone meal, aragonite (seashells), wood ash and soft rock phosphate.

(Mg) Magnesium is component of the chlorophyll and aids plants in the process of photosynthesis. Peppers, potatoes, and tomatoes require high levels of magnesium. Generally if you add compost, aged animal manure or plant matter to you garden soil in the Fall and Spring, your soil should have sufficient amounts of magnesium. If a soil test reveals otherwise, Epsom Salts are a highly soluble form of magnesium sulfate.

Minor Trace Elements, a.k.a. Micronutrients, include: (Fe) Iron, (Mn) Manganese, (Cu) Copper, (Zn) Zinc, (B) Boron, (Mo) Molybdenum, and (Al) Aluminum.



SOIL ACIDITY (pH)

The scale ranges from 1.0 to 14.0, but soil most often ranges from a 3.0 to a 10.0. 7.0 is neutral. The lower the soil pH, the more acidic it is, and the higher the pH more alkaline it is. For vegetable and herb gardens, a soil pH of 5 to 7 is ideal. Sulfur and calcium amendments can help shift soil acidity in the direction your plants need.



CONTAMINANTS

If you live in an urban area, your soil may contain traces of fuel components, such as benzene, toluene, xylene, and petroleum hydrocarbons, and/or what are known as Extractable Heavy Metals which include (Pb) Lead, (Cd) Cadmium, (Ni) Nickel, and (Cr) Chromium. Because cities tend to have higher populations in closer spaces, paint flakes from houses, emission pollution from cars, industrial processes, rain runoff from roads and highways, and litter are bound to collect and build up in city soils. These contaminants can be hazardous to your health, and especially that of children. A soil test is a great and necessary investment in the health and well being of all who tend in your garden and eat its abundance. Do not be discouraged by the soil test results. If you have a worst-case scenario, grants may exist for environmental clean-up or brownfield land restoration. Contact your local congressman for more information about what funds and resources might be available to you. If it's somewhat bad, but not exceedingly dangerous, raised beds and container gardening may be your solution, or you can excavate the contaminated soil out, and bring in healthy soil and heaps of compost.



HOW TO HAVE A SOIL TEST DONE

Check your state university's cooperative extension to see if they have a soil testing program. University of Massachusetts Amherst's Department of Plant and Soil Sciences is noted for having an excellent soil testing program. Each program will offer its own set of instructions. The fees are minimal considering the wealth of information you receive. Generally all you need is a clean spade and some heavy duty ziplock plastic bags. You will take random samples throughout your gardening space, mix them together, then air dry them, and mix again. Seal a sample from the mix in a ziplock bag, labeled with the required information, and mail it to the testing location with a brief note outlining any comments about your gardening needs (such as specific crops or prior land usage history), questions or concerns you might have. After the testing is finished, you will receive a report outlining your soil health and any necessary measures needed to boost it.



SOIL AMENDMENTS

Often you have soil amendments available to you for free in the form of vegetable scraps, grass clipping, dried leaves, coffee grinds, seashells, eggshells etc. But if you are looking for a specific soil amendment, like Gypsum, check you local nursery or gardening center for organic options, or order online from a supplier like Planet Natural.