Dorothy is a master gardener, former newspaper reporter, and the author of several books. Michael is a landscape and nature photographer.
Help Your Plants Achieve Their Full Potential
When the ground begins to warm up and your plants are ready to begin strutting their stuff, you may be stifling them if your soil is less than desirable. Those many hours of enjoyment you had been planning may turn into long hours of hard work, only to see your plants underperforming. The best thing to do is prepare the soil BEFORE you plant.
Soils are based on mineral particles that are formed when rocks break down naturally. In all soils, there are also varying amounts of water, organic matter, air, and even some living creatures like bacteria, fungi, earthworms, and countless others. The basic characteristics of all types of soil are determined by the size and shape of its mineral particles.
The makeup of most garden soil falls somewhere between two types of soil - sandy and clay - which is a good thing. If your garden has an extreme amount of either, however, you need to plan to amend it. If you know nothing about amending your soil, this article should help.
Learn the pH of Your Soil
Alkaline Soil vs Acidic Soil
Your soil can be acid, alkaline, or even neutral. You can buy a kit at just about any garden center (Home Depot, Lowe's or WalMart), or on Amazon.com that will allow you to check your soil's pH (a ballpark figure), and having that knowledge is extremely helpful.
Soils that have a pH below 7 are considered acidic. Those with pH above 7 are considered alkaline. If you live in an area of little rainfall and dry summers you probably have alkaline soil. In areas of significant rain where the summers are humid the soil is more than likely acidic.
Extremes of either acidity or alkalinity can be problematic for gardeners because nutrients become chemically unavailable to plant roots, so even having a ballpark idea of your soil's pH can be a valuable bit of knowledge. If you feel like you need a more exact measurement of your soil's pH, there are analytical laboratories you can contact (they are in the yellow pages) or call your local Cooperative Extension Office. Those more in-depth tests can advise you of any nutrient deficiencies in your soil and the lab will advise you how to correct any problems you may have. The lab will tell you when and how to collect a sample.
There are, however, plants that require somewhat acidic or somewhat alkaline soils, but most annuals and perennials grow well in soils that range from moderately acidic to somewhat alkaline.
Is Loam the Holy Grail of Soil?
The Best Soil Is Called Loam
Very few of us are blessed with perfect soil, and you will be better off choosing plants that are naturally suited to the type of soil you have. If there are particular plants you are interested in growing, you will need to learn to amend your soil with the proper combination of organic materials. In the end, the best kind of soil you can have is loam, the medium in which most plants will thrive.
Loam is dark soil that has an earthy (almost sweet) fragrance. If you squeeze a handful together in your hand, it will clump together, but crumble easily when sifted through your fingers.
Advantages of Loam
- Fertility and stability for plant roots are supplied by the clay and silt particles in loam by absorbing and holding moisture. They also help the soil's particles stick together, holding soluble plant nutrients in place for plant roots to absorb.
- Sand particles, on the other hand, loosen the texture of the soil, adding vital spaces (pores) so air and water have access to the root zone.
- Organic matter in the soil helps to lighten the texture of the soil, boosting the fertility and moisture-retaining capacity.
All of the above ingredients together form a crumbly, moist, fertile soil that drains well, and if a healthy, beautiful yard is your goal, you can't ask for anything better than that.
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Sandy soil is light and has large particles and large pore spaces, which allow important nutrients and water to drain away all too quickly. In sandy soil, you might not ever have to deal with root rot, but you will have to water your plants more often in order to keep the roots moist. Fertilizers you may have used will be leached away quickly as well, so you will need to replace those nutrients more often.
Amending Sandy Soil
Water runs out of sandy soil very quickly making it difficult for the soil to retain the nutrients that plants need. Your goal in amending sandy soil is to add material that will increase the ability of the soil to retain water and increase nutrients. The fastest way to do both is to add well-rotted manure or compost to the soil.
Clay soil is heavy and made up of tiny particles that pack together to produce a compact, tight mass with only microscopic pore spaces. The soil will drain very slowly because the nutrients and water percolate slowly through those pores. Roots have a difficult time piercing clay soil, and in times of heavy rain, you always run the risk of having root rot because the soil remains saturated.
The job of working clay soil is not an easy one. It is either terribly sticky when wet, or as hard as a rock when dry. The only plus to this type of soil is that you are able to water and fertilize less often because the soil drains so slowly.
Amending Clay Soil
Because clay soil is extremely dense, drainage (or the lack of) is the biggest problem for gardeners. The majority of all clay soils are on the alkaline side, which means you'll probably need to lower the pH of the soil and there are many different ways to do it. You can add any of the following: builder's sand, gypsum, composted manure, compost or other coarse organic material.
- Builder's sand and gypsum added to the soil forces the particles apart allowing for increased water drainage and air pockets. Always use coarse builder's sand. Using fine sand will only make things worse.
- Organic matter can help your plants get the proper nutrients and build increased humus with additional microbes that are crucial for good soil. The organic matter will also help lower the pH of the soil.
- Your goal should be to add an equal mix of coarse sand (builder's sand) and coarse organic material.
If You Need to Raise the pH Level of Your Soil
Maybe you need to raise the level of your soil's pH. Altered pH levels are difficult to maintain, so you should plan to check your soil each year and add the necessary amendments. This is a list of the easiest and best amendments if you need to raise the pH level of your soil:
- Composted manure (from herbivores) has a neutralizing effect on all types of soil, but be sure the manure is well composted to reduce the concentration of nitrogen compounds that are found in fresh manure (they will damage and burn your plants).
- Limestone (ground into powder or pressed into pellets) can help lower your soil's pH, but the pellets are easier to measure accurately and are more predictable than limestone in the powdered form.
- Crushed oyster or clam shells are alkaline in nature, plus the calcium in the shells is a nutrient, making them great additions to vegetable gardens.
- Wood ash collected from wood-burning stoves and fireplaces will not only raise the pH of the soil it is also a course of potassium, calcium and some other minor nutrients.
Note: If you grow mushrooms, try adding the spent medium to your soil. The slightly alkaline pH raises the soil's pH and aids in stabilizing the altered pH.
If You Need to Lower the pH of Your Soil
The following list of mineral supplements will help you to neutralize alkaline soil:
- Uncomposted oak leaves, peat moss, and pine needles will neutralize as they decompose.
- Garden sulfur, usually in a powder form is fast-acting elemental sulfur that can lower the soil's pH.
- Adding either compost, manure, or organic soil amendments like alfalfa meal to the soil can help drop pH over time by increasing the bacterial populations. Adding organic matter not only increases microbial life it improves the structure of the soil.
How to Determine Drainage
Most plants require well-drained soil, and before you plant, you need to know just how your own soil drains. In order to find out, dig a hole that is about 18"deep and fill it with water. Once that water drains, fill it once again with water. If the second amount of water drains completely in an hour or less, you have good drainage.
On the other hand, if after several hours, the water is still standing in the hole, you have soil that drains poorly. Your choices are limited at that point. You can either add organic matter to help improve the drainage or plant somewhere else. If your entire yard drains poorly, you may want to consider planting in raised beds, and your choices in raised beds and the type of plants that can be grown in them are endless.
- The Garden Problem Solver - The Ultimate Troubleshooting Guide for Successful Gardening (1999), Reader's Digest Association, Pleasantville, New York/Montreal.
- Annuals and Perennials (2002 Second Edition), Sunset Books, Sunset Publishing Corporation, Menlo Park, California.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2019 Mike and Dorothy McKenney
Pamela Oglesby from Sunny Florida on January 20, 2019:
Good information on soil. Ours is sandy so we have added better top soil and we always us mulch. You are right about the need for water. Thanks for the information.
Mike and Dorothy McKenney (author) from United States on January 19, 2019:
Oluwafemi Okeowo from Nigeria on January 19, 2019:
Excellent post on garden soil, Mike and Dorothy McKenney!