Balance in the Soil - Amendments and Their Kin

Updated: Oct 9, 2018

The Basics Series, as the name suggests, is a series of articles that lay out some of the basics of gardening and plant care – Soils, Mulches, Planting and Staking, Roots & Water, and Plant Fertilization. Our hope is that this series will be accessible to the beginning gardener while also offering some additional information that will prove valuable to those who have been digging in the dirt for a little longer (first lesson: dirt is what’s tracked onto your carpet, soil is what we plant into). If, along the way, you would like additional information on a particular subject, or if you have suggestions for additional blog posts please feel free to leave them in the comments below.

In the first post of this series on gardening basics I wrote about some of the complexity that makes up the soil in our gardens. The general idea was that without some basic understanding of soil’s complexity, gardening simplicity is simply unlikely. Green side up is not enough.

After mentioning some of the ingredients found in good soil and the function of those ingredients, I promised to follow up with another post on balance in soil for the benefit of those who believe their soil may be out of whack. So what is balance? Balance, in the context of garden soil, can be considered “a right amount of the right stuff in the right place for the right plant”. Sounds dodgy, I know. But let’s pick that definition apart and see what’s inside.

As mentioned in the last post, soil has many different components or ingredients – sand, silt, clay, organic matter and debris, microbes, earthworms, etc. - each with their own purpose. Some of them are already in the soil. Some of them we add. The ingredients are the stuff. Some ingredients hold water while others let it drain. Some are organic and some are not. Some feed the microbes, others serve the plant. Some are good and some are bad. Balance. And balance means the right amount of the right stuff. Too much of one thing can lead to problems with your plants just as well as too little can. Too much water: bad. Not enough water: bad. Balance. And not only that, some of the stuff needs to be in the right place. If you are going to use a fertilizer on your rhubarb or your boxwood, that stuff needs to go in the right place. If you use a granular fertilizer or even a hot compost in the wrong way your plants are likely to burn up. Furthermore, if your soil conditions are perfect for one plant, that doesn’t necessarily mean it is perfect for another - try growing rice in the desert or a rose in a swamp. Balance. A right amount of the right stuff in the right place for the right plant.

Before we get into more of the specifics of balance, I want to assure you that unless you’re living in the desert or in a swamp, most of what your soil needs to produce vibrant plants is already present. If not, amending the soil to compensate for its deficiencies is usually a pretty simple and relatively inexpensive endeavor. And to further set your mind at ease, there aren’t any major differences between the needs of a vegetable garden and a landscape planting as far as soil goes. “So how do I know what my soil may need?”

Healthy soil next to deficient soil
Healthy soil next to deficient soil

Digging in the Soil

Here are a few steps you can take to get an idea of your soil’s health.

  1. Observe it. What is growing right now in the area that you’d like to plant? If there are a multitude of weeds, you may have your work cut out for you in pulling them, but their presence likely already suggests that your soil won’t need much help. Do the weeds (or whatever plant may be there) have good green leaves? If so, they can probably be removed and the soil can be counted on to grow most anything you want. But if they have bright green veins and pale-yellow margins (the part of the leaf between the veins) or vice-versa, your soil may be lacking some nutrients. We’ll get to solutions a little later on.

  2. Dig it. Grab a shovel and dig a hole about 8-10” deep. How does the soil look? Is it pasty? This probably suggests that there is too much clay and a lack of organic matter. Is it dark brown or black? If so, you probably have a good balance of the necessary organic matter in the soil (strive for 8” of dark soil in a vegetable garden, 4-5” in a landscape). If you squeeze a slightly damp fistful, does it clump together or does it fall apart? The answer to this can indicate whether there is too much or too little sand in the mix and will often indicate the drainage capacity of the soil. Does it smell bad? Soil that drains poorly will usually lead to anaerobic (without oxygen) fungal and bacterial populations (bad) which cause the soil to smell like sour rot. Are there any earth worms? The presence of worms usually suggests that good organic matter is present - and where there is organic matter, the microbes that we want to cultivate are always present.

  3. Water it. Fill the hole you just dug with water. If it’s still full of water at the end of the day, you’ll likely need to amend it. If it drains as quickly as the water comes out of the hose, you either have a hidden cave beneath your backyard or you have a very sandy soil. Either way, you’ll need to amend it (good luck with the cave!).

As you’re looking at your soil and answering the questions above, understand that you’re really only looking for two main characteristics – organic matter and drainage. The top several inches of soil need to be characterized by these two. And everything else will be determined by these two. These are what bring the balance to your planting area. If you have a good balance of organic matter, the microbes will be there continuing to break minerals down into a form that’s usable by plants. They will also contribute to cultivating the soil at a micro-level – adding pore space and breaking up the clay. If you have good drainage, you can rest assured that your inorganic matter (sand and rock bits) are well balanced. Good drainage also indicates that pore space (air) will be readily available for the plant and that you don’t have the wrong kinds of fungi and bacteria (anaerobic).

Make it Right

If you’ve made it this far and you’ve discovered that your soil is pasty, smelly, poorly draining and seemingly fit only for the most resilient of dandelions here are some amendments you can add that will improve your soil in short order. Reading through these should help you understand what it is you need to add to get your soil and all the life beneath and around the plant roots (rhizosphere) back to good, productive health.

Mulch. Probably the most recognizable soil amendment, mulch comes in many forms. Though we usually think of wood when we think of mulches, some people use decorative stone as a mulch. Before describing the differences between the mulches, let’s consider some of the benefits that the right mulch can add to the soil and, thereby, the garden or the landscape.

The right mulch can perform four much needed services – moisture moderation, temperature moderation, weed control, and soil building. We’ll look at these one by one.

  1. Moisture moderation. As alluded to earlier, the plants you hope to grow will respond best to a soil that doesn’t stay waterlogged yet doesn’t dry out too quickly. By either incorporating (tilling) natural wood mulch into the top several inches of soil or top-dressing the planting area with it, natural wood mulch will both retain some moisture, allow excess moisture to drain away, and keep pore spaces open.

  2. Temperature moderation. Most living organisms prefer a relatively stable environment with regard to temperature. Extreme fluctuations can cause issues for plant roots just as they can for you and me. A top-dressing (1-3” depending on the circumstances) of mulch will reduce the scorching/drying/baking effects of the sun. That same top-dressing will also keep the damaging freeze and the frost that much further from the roots of the plant.

  3. Weed prevention. Though not the surest method of weed control, several inches of either wood or stone mulch can hinder weed growth by bringing so much pore space that when a weed seed tries to germinate, its initial root will often wither and die due to a lack of sufficient moisture.

  4. Soil building. This, unfortunately, is usually least considered by homeowners when they’re determining what type of mulch to use. A good mulch will break down into finer particles. Yes, this means it will need to be added to on some type of continuing schedule, but the benefit of soil building and the vibrancy of the plants due to this practice should be factored in to the decision. As the mulch breaks down, it continually adds organic matter to the ecosystem beneath the soil. This organic matter continually feeds the microbes that are necessary for plant health. Beyond this, it adds proper structure to the soil – soil that is re-mulched on a yearly basis has a less compact structure which makes it better for the roots trying to grow through it and the moisture/pore space that needs to be maintained.

So, with understanding what benefits the right type of mulch can provide, let’s consider the pros and cons of the three main types of mulch.

decorative stone mulch
Stone mulch

Stone mulch. What’s good about it? It’s durable. You can expect a decorative stone mulch to remain in its present form (you won’t need to replace it unless it sinks into the soil or the neighborhood kids use them as torpedoes) for the next million or so years. It’s also colorful and may add a new texture to the landscape. What’s bad about it? It doesn’t moderate the moisture content of the soil. It absorbs and holds heat from the sun long into the night, depriving plant roots of any respite on those hot summer days. It’s not a suitable weed preventer *(see note on landscape fabrics below) and it does nothing to contribute to the soil, organic content, or the microbes that need to be fed to produce healthy plants. Beyond this, it’s fine.

Dyed wood mulch. Dyed mulch – the red and black and darker browns – are made of chopped shipping pallets that are mixed with a colorant (dye). What’s good about it? It may possess colors that aren’t available in all the rest of creation. It may also contain colors that are darkened versions of natural colors. It will also last longer than natural shredded mulch. It will contribute to temperature moderation and weed prevention as well as natural wood mulch. What’s bad about it? The process. Shipping pallets are kiln-dried to assure longevity and sterility. Wood that has had all of the microbes cooked out of it (rendering it sterile) will not decompose nearly as quickly as uncooked wood. This is good for shipping companies as pallets that are breaking down into soil would defeat their purpose. But it’s not so good for gardens. Baked and dyed wood won’t maintain moisture as well as natural wood since its structure has been altered reducing pore space and pliability. More importantly, it won’t assist with soil building as well as a natural product since it breaks down much more slowly.

Natural Mulch
Natural Mulch

Natural wood mulch. Often referred to as shredded hardwood or hardwood bark, natural wood mulch serves the garden best in the four categories listed above – Moisture and temperature moderation, weed prevention, and soil building. It moderates moisture and temperature well, does a fair job of weed prevention and does exceptionally well for soil building. I probably don’t need to mention which mulch I prefer so we’ll move on to the other soil amendments.

Peat Moss. For a single planting hole or a very small area to be planted, peat moss can improve the drainage and moisture retention of your soil. It is also fairly acidic so it will be appreciated by azaleas and rhododendrons and other acid loving plants. As far as nutrients go, peat moss doesn’t have anything to offer.

Compost. Or Composted Soil. This dark brown or black, fluffy, woodsy smelling heavenly goodness could well be considered the tonic your soil needs for whatever ails it. Composting is the process by which both mechanical and biological process are used to break leaves, twigs, grass clippings and other small debris down into a product that looks closer to soil than to yard waste. In whatever form it is available, compost will add the necessary microbial life to your garden while also contributing to the soil structure. The only caution that may be necessary is to be aware of the condition or age of the compost. In the composting process, the temperatures inside of the compost heap can reach well over 200 degrees. This heat is caused by the microbes working on all of the debris – fascinating stuff, but bad for your skin. The larger problem though can come from the wildly nutritious value of fresh compost. When top-dressing or incorporating fresh compost into your planting area make sure to keep it off the leaves of the plants and don’t pile much near or on the root system of the plant. Just as with synthetic fertilizer, compost can burn some plants due to its high nutrient value. Don’t worry, all that heavenly goodness will dilute and work its way to the roots within a few days or after the first good rain. It’s best if compost is aged for a year before using it in the garden or landscape. If you are adding compost to an unplanted area, you can add an inch or two on top of the soil and either let it work its way down into the soil or, better, you can till it in to a depth of 4-5”. Other than that, compost away!

Fertilizer. Some planting beds and gardens have produced far more than they’ve been given. The vegetables they’ve offered and the flowers they’ve produced year after year have used up most of the nutrients in the soil. If the soil structure still seems to be in good shape – it’s not sticky and maintains moisture pretty well, you may consider adding synthetic fertilizer to your beds. These are available in more formulations than can be listed – fertilizer for roses, fertilizer for apples, fertilizer for nut trees, fertilizer for annuals, and vegetables, and turf – so do a little research before you head out to buy it. Also, keep in mind that the need for frequent fertilizer use likely suggests that the soil is lacking in some other areas. Incorporating some mulch or compost into the soil if you’re able will provide a solution that doesn’t involve so much fertilizer. Also, always read and follow the fertilizer labels. More is not better when it comes to fertilizer. Using too much can and often will lead to burned, dead plants. Read the directions.

Drainage. Drainage has been mentioned several times in this post and the first in this series. Sometimes the solution to drainage problems involves redirecting water from the planting area. Sometimes adding or incorporating mulch or compost can solve the problem. Sometimes, if the area is small enough and your back is strong enough, incorporating sand into the planting bed may be a solution. I’d try the other suggestions first.

Make it Better - Rinse and Repeat

Sometimes the mouthwash doesn’t do all that you’d hoped it would. Sometimes your hair can get so filthy while gardening that a single shampooing doesn’t cut it. Rinse and repeat. Adding amendments to the soil, and the maintenance of good, productive soil is not a once and done proposition. As I’ve mentioned, the microbes are going to process good soil, your plants are going to use what they produce and sooner or later you’re going to need to do it all again. You start with making it good but should always plan on making it better. If you have a vegetable garden, consider leaving the plants in the garden to decompose at the end of the season. Also consider tilling them in prior to planting next spring. This not only gets all of the organic matter spread out but it also reduces soil compaction which can lead to further problems. Starting a compost pile is as easy as throwing all of your yard waste and spent vegetables into a pile behind the shed. If you turn it occasionally, it should be a fine soil amendment by planting time next year. Do you need to add heaping tons of good stuff every year? Probably not. Just keep an eye on the condition of the soil and make sure that you have the right amount of the right stuff in the right place for the right plant. And when it’s time, rinse and repeat.

* A note on landscape fabrics and weed barriers. The intent of weed barriers and landscape fabrics and plastics is a noble one: with a very small financial investment and a little time spent you can have a weed-free landscape. You simply roll out the fabric and cover the bed that you’ll be planting so the weeds can’t get through. The problem?

The problems:

  1. Reduced water. Water, following the path of least resistance as it does, does not simply sit on top of the fabric until it can gently soak in and get to the roots beneath. The use of weed-barriers, even though they’re often sold as permeable, will reduce the amount of rain water that gets to the root system of your plants and its use will reduce the amount of irrigation or hose water that gets to them. Unless your planting bed is perfectly level, water will follow the path of least resistance – away from your plants.

  2. Dying soil. As I’ve mentioned, good productive plants are a result of good productive soil. And good productive soil gets to be what it is due to you and I continually feeding it – most often with a natural mulch. Perhaps the greatest benefit of mulch occurs as it decomposes and is worked into the soil beneath. Weed barriers prevent this transaction from occurring. A good mulch will still decompose but the benefits to the soil and the microbes beneath are reduced by nearly 100%. If you are preventing the improvement of your soil, you’re also preventing the microbes from making your garden work and they will, with time, leave. Evidence of this can be seen beneath the weed barrier of any landscape that has been covered this way for a few years. The soil beneath will be pale (devoid of organic matter), clayey, poorly draining and not suitable to support thriving plants.

  3. Asphyxiation. Yes, death by choking. The process for laying down weed barriers usually involves cutting a circle or an “X” in the fabric where the plants will pop through. The problem is that most plants grow and multiply. As they do, and when they encounter the fabric, the fabric – though we’d think it would tear to allow plant growth – end us girdling the plants. It becomes so tight around their throat that growth is hindered and decline can be expected.

Other than those few issues, it’s a fine product. Not.

Pale, pasty soil beneath weed barrier
Pale, pasty soil beneath weed barrier

Read More in The Basics Series

The Basics Series: Understanding Soil

The Basics Series: Planting and Staking

The Basics Series: Roots and Water

42 views0 comments