09 Aug 2014
Traditionally, fields were allowed to lie fallow every few years to let the soil recover from being plowed and all the nutrients stripped out. Whatever wanted to grow up would be left alone; the field, as it recovered might have been used for pasture. The cows or sheep would fertilize the soil with their manure. After a few years, the pasture would be plowed under again and sown with a grain crop.
When you do this — let a bed lie fallow for a year or two — you do not have to let Nature decide what plants will grow. You can buy cover crops as seed mixtures. Catalogs like Johnny’s Selected Seeds have a wide range of choices depending on your geographic area and soil needs. A dedicated cover crop will have a mix of plants that will fix nitrogen, and have deep roots to break up hard packed soil. Deep rooted plants can also bring up nutrients from deep in the earth. Let the plants grow, chop them up before the first frost, turn them into the soil and they will die, rot in place, and return all their fertility back to the bed for next year’s tomatoes. Real farmers do this to improve their soil and so can you.
Plants need many, many kinds of nutrients to grow and produce vegetables. If one element is lacking, then no matter how rich your soil is otherwise, that one missing element will determine how well your crop grows. You can have your soil tested to see what you have and what you are missing.
The first, basic test you can do yourself with a glass jar and some water. Fill the jar about one quarter full with soil. Fill the jar almost all the way with water. Shake vigorously until soil and water are fully mixed. Let the jar sit, undisturbed, for a few days to settle out. The contents should settle out in layers, with heavier rocks and sand in the bottom, topped with clay particles, then silt, and finally, any organic matter at the top. If you see a lot of sand, you have sandy soil. If you see a lot of clay, well, you know. You hope to see a thick layer of organic humus on the top. There probably won’t be much at all. Do this test in several locations in your yard, as it is very unlikely the soil will be the same everywhere. You want to dig down an inch or two to get your sample as this is where the plant roots will grow.
To get more in-depth information, you will need to purchase a soil-testing kit. Every garden center has them. Follow the directions carefully and you will have a better idea of what you are missing, what you have, and how acidic the soil is. You can also get your soil tested by a laboratory. The local county agricultural extension agent will be able to tell you who to contact in your area. Some states do this for free, other states charge a fee depending on how much you want to know.
The information you get will tell you if you are low on any of the big three elements: potassium, phosphorus, or nitrogen. You will then get a long discussion of micro-elements and suggested changes and amendments. Missing micronutrients, like the big three, can be added to your soil by spreading various amendments. The lab report will tell you which ones to buy at the garden center. We were low on calcium which is easy to supply. Save all your egg shells, crush them fine, and sprinkle them everywhere. They disappear fast and the worms incorporate them into the soil.
The testing will also tell you the pH level of your soil; that is, how acidic or alkaline it is. The pH level determines what plants will grow joyfully, which will die a lingering resentful death, and which will struggle along but not quite die. As an example, blueberries insist on a very acid soil. It is really hard to permanently adjust the pH of soil so your blueberries may have to be grown in containers if your soil is more alkaline. Grass likes a more alkaline soil; spreading lime is a way of increasing the alkalinity of your soil to make the grass happier. Acid liking plants won’t appreciate the lime from your lawn leaching over into their beds every time it rains.
You can add all the soil amendments you want and you can fertilize all you want, but your soil will not come to life without decaying organic material. Compost, decayed leaves, grass clippings and any other rotting organic materials you can scrape up are what feed the microscopic zoo. You will keep coming back to having to add more organic matter to your soil.
A heavy clay drains poorly and can get waterlogged, drowning the plant roots. That is, if it accepts rainwater in the first place. Clay can harden and bake into a bricklike consistency. Water rolls off of it without soaking in. Sand drains and drains and holds no moisture at all. Roots get plenty of air but they die from dryness. The cure for both conditions is compost, leaves, mulches, and any other organic material you can layer onto the soil. Of the two, I like clay better. It is harder to amend at first but it retains moisture better and has more available minerals. Sandy soils burn through compost at a much higher rate than clay. The drainage is better but plants dry out quicker because of that.
This is where knowing what your soil is like will help you garden better. If you know your soil is sandy, then you want plants that like it drier. A heavier clay soil shouldn’t be planted with things that demand perfect drainage. Clay does tend to have more minerals available naturally in it and it will hold moisture better when heavily amended with humus. If you don’t add loads of leaves and compost to clay, it turns into concrete and repels water like a brick would. Sand will always drain beautifully. In fact, it drains so well that your plants will be gasping for water and starved for nutrients as everything you want to help them grow will leach down, down, down into the subsoil where much of the root systems won’t reach. Compost, compost, and more compost will fix sand AND clay problems.
The beauty of a raised bed is that you can completely change the soil from what is in the surrounding areas. Think of raised beds as giant pots that are open at the bottom. If you want to grow something like blueberries and you do not have very acid soil, a raised bed with custom mixed soil is the only way to succeed. I tried to grow blueberries and despite regular applications of pine straw, coffee grounds, and Holly-tone (a fertilizer for acid loving plants like azaleas, hollies, and blueberries) I could not change the overall pH of the soil. The blueberries are gone, replaced with hazelnut bushes.
Don’t use inorganic mulches like gravel or shredded rubber. They do nothing to improve your soil so what is the point of having them? Any mulch that was once alive will rot down and improve your soil. I think the difference between mulches and compost is mulches tend to be woodier and heavier. Think chunks of twigs and wood chips as opposed to something that is as fine as potting soil. Leaves are free and readily available every fall. Grass clippings are free, readily available but should be dried out or composted prior to use. Branches, whole shrubs, old Christmas trees can all be broken up, by hand or with a chipper and spread out as mulch. It will take longer to rot down than leaves but it will do so, eventually. Pine needles rot down. Newspaper rots down. Big bags of shredded documents will rot down but are better mixed into your compost bin so they don’t blow all around. Wood ashes can be composted and so can sawdust. Nutshells, cocoa pods, Halloween hay bales, straw, seaweed, spent mushroom compost, anything that was once alive. If a landscaper or the power company is working in your area trimming trees, stop and ask for the chopped up leaves and branches. Chances are they will be happy to drop it off in your driveway so they don’t have to deal with the stuff themselves.
Look around at the possibilities for soil building. The sooner you begin adding rotting plant matter to your garden soil, the better it will become. Make soil building a regular part of your garden routine and your improved soil will reward you with healthier plants, both in the growing and in the eating. Don’t ever stop adding leaves and compost. You can never have too much humus in your soil. The better your soil, the less dependent you will be on expensive artificial fertilizers to feed yourself and your family. You don’t want to use them anyway as they are very damaging to the soil communities and eventually, they kill many of your soil critters. Feed your soil and it will feed you.
Read About Soil Building
Let it Rot!: The Gardener’s Guide to Composting; Stu Campbell; Storey Communications, Inc.; 1975
Mike McGrath’s Book of Compost; Mike McGrath; Sterling Publishing, 2006
Cows Save the Planet: And Other Improbable Ways of Restoring Soil to Heal the Earth; Judith D. Schwartz; Chelsea Green Publishing; 2013
Feed the Soil: Rodale’s Complete Guide to Soil Improvement; the Editors at Rodale Press; Rodale Press, 1992
Gardener’s Guide to Better Soil; Gene Logsdon; Rodale Press, 1975
The Soil Will Save Us: How Scientists, Farmers, and Foodies Are Healing the Soil to Save the Planet; Kristin Ohlson; Rodale Press, 2014