Are soil amendments necessary?

Are soil amendments necessary? What you need to know about using them and how to save money on them.

It’s very, very easy to spend a lot of money gardening. Even frugal gardeners can end up spending more than they plan, especially as the season progresses. I’m going to talk about some of the unexpected expenses that can come up during the growing season. Some of these are avoidable with planning but some are not. Here’s some of the garden costs you might not have thought about AND how to cut your garden expenses.

Part one: Soil Amendments and Fertilizers-  What are they, what do they do and do you need them?

What Are Soil Amendments?

Soil amendments are anything you add to your growing plot to make the soil better. Sometimes, that means adding things like sand, sawdust* or coconut coir to improve soil texture. Other amendments like wood ash or pine needles** are intended to raise or lower the PH of soil. And sometimes, amendments serve as food for hungry plants or add nutrients back into soil.

There’s some overlap between amendments for texture and amendments for nutrition.

Can you garden without using soil amendments?

It’s a reasonable question. After all, if you’re already got ‘dirt’, why not just put your plants in it and let them do their thing?

Some gardeners are incredibly lucky and their soil is a mix of clay, sand and loam. That means it has a great texture for growing many plants – the soil doesn’t hold too much water but also doesn’t dry out too quickly. It doesn’t get so hard or compacted that plants have trouble growing deep roots. In a perfect world, that’s the soil all of us would have for the majority of our plants.

In the real world, most of us have soil that is too hard or too dense or too sandy. Or we have soil that’s great for some plants, but not right for others.  When that happens, plants often fail to thrive, or even die. While you can choose to simply work with your soil as it is, you risk losing plants or having very low yields. In the long run, not amending soil to save money can cost you a small fortune in lost yields and replacement plants.

Often, adding compost each year will address soil texture while also restoring soil nutrients. More on that below.

But if you want to grow plants like lavender or rosemary, or other dry-climate plants, you will likely need to add some coarse sand to the planting area. If you prefer not to deal with soil amendments, then look for plants that will grow well in your soil in its current state.

*only from untreated wood. Check to make sure the tree species isn’t allelopathic. 

**pine needles and other ‘acidifiers’ only offer a temporary boost to acidity, at best. And they take a long time to break down. Mulch with them or add them into a planting hole if you wish, but don’t assume they’ll be able to single-handedly change soil Ph. 

Do I have to add fertilizer?

Note, fertilizer is not a soil amendment. But supplemental fertilizer is related, so I chose to include it in the discussion about amendments.

Again, the answer is that you certainly don’t have to provide any supplemental nutritional, fertilizers or amendments. But soil that is nutritionally deficient isn’t going to support healthy plants. And if you’re growing fruit or vegetables, starved soil will make it very hard for your plants to produce much. This can be an even bigger problem if you can’t or don’t rotate your vegetable plants.

Let’s chat for a second about compost vs. fertilizer. Both of them CAN provide nutrients that your soil is lacking. But they’re not the same thing and they shouldn’t be used interchangeably.

Fertilizer is usually applied once the plant is growing and is designed to provide a burst of nutrients that will be available to the plant in short order. Many fertilizers are given in liquid form, so plants draw them up and use them quickly. Others are dry, like granules, powder or stakes and release their components gradually. No matter the format, fertilizer is ‘food’ for the plant, not enrichment for the soil.

Compost is simply organic matter – things like spent plants and cardboard or food waste – that has been allowed to breakdown into a crumbly, uniform mass. It resembles soil, superficially. Compost is usually added at the beginning or the end of the season. It’s purpose is to help the soil replenish both macro and micro nutrients but it also improves soil texture. You can also add compost to the soil around a plant (called ‘top dressing’) to help conserve moisture in the soil and slowly leech nutrients into the ground. While compost may indirectly provide nutrients to a plant, it’s primary purpose is to enrich the soil, not the plant.

So do I have to use them?

It really comes down to what you’re trying to grow. If you’re growing fruit and vegetables, big flowering shrubs, or long-blooming annuals/non-native perennials, you may need to use fertilizer. Those plants need a LOT of nutrients to produce, and they need them quickly. Even if your soil is very fertile and healthy at the start of the season, some of those plants can deplete essential nutrients before the season is over. When that happens, you need to ‘feed’ the soil so the plant can keep producing.

It’s not a sure thing, though. And  it depends on the plant in question and your own particular micro-climate. Before using fertilizer, read up on the plants in order to learn what supplemental fertilizer they may need and when they need it. It also depends on the weather. An unusually hot and dry season can affect how plants grow and how they use nutrients. A summer with the perfect amount of rain and optimal temperature can increase fruit or vegetable production, which might consume soil nutrients more quickly.

Thoughts on using fertilizer

If you’re serious about growing any of the plants I mentioned above, it’s best to at least prepare for the possibility that you’ll need to give them fertilizer at some point in the season.

I would encourage you only to fertilize plants when absolutely necessary and to use fertilizers that are derived from natural sources of nutrition (think fish emulsion, bone meal or compost tea). Avoid synthetic fertilizers. In the long run, they can wreak havoc with your soil and they run-off into municipal water, causing huge ecological and environmental issues.

Before you use any fertilizer, make sure it’s the correct type and strength for the plant in question. Over fertilizing or using the wrong formula is worse than not fertilizing. Look at the NPK ratio for each fertilizer and make sure it’s suited to the task at hand.

Ideally, get a soil test before you add either amendments or fertilizers. The soil test will give you some basic information on the current levels of Nitrogen-Potassium and Magnesium in the soil, as well as the Ph level. If you’re unable to get a soil test, look at your plants for clues to their nutritional needs. The color and appearance of leaves is a great way to judge possible deficiencies.

What about adding Epsom salt or egg shells to my soil?

There are a lot of people on the internet who swear by Epsom salts or coffee grounds or egg shells as plant enhancers. The bottom line is that most of these ‘remedies’ are anecdotal, at best. Epsom salt likely has no effect on plant size or health. Egg shells WILL eventually break down and might add some calcium to the soil, but by the time they do, your current plants will be long gone. Coffee grounds are a source of nitrogen and might temporarily raise the acidity of soil, but they’re not a long term solution to soil that’s too alkaline.

If you want to put egg shells, coffee grounds or other things into your soil, you’ll get more mileage out of composting them first. Or, if you happen to have chickens, feed the hens their ground up eggshells and put them back into your soil via composted manure. If you have composting worms, they love coffee grounds, so that’s much better use of them.

What else do I need to know about compost?

Compost is a soil amendment that improves both soil texture and nutrient level. Adding it regularly provides long term benefits to soil structure and soil biology.

If you grow vegetables, fruits (trees or bushes) or annual flowers, you should really consider adding compost to those beds each year. As mentioned, annual crops that make a lot of flowers, fruit or vegetables are ‘heavy feeders’ and deplete soil nutrients. Putting a thick layer of compost over those beds at the end of the season or very early in the spring helps restore nutrients. And the organic matter helps the soil stay loose and loamy, which is important to the long-term health of your garden.

Hardy perennials likely won’t need compost every year, though some can benefit from a side or top dressing.

Buying quality compost from a reputable source may be a garden expense you weren’t expecting. But it can dramatically improve the health and success of your garden. While it’s not, strictly speaking, essential, it’s one of the best bangs for your buck when it comes to improving both soil texture and fertility.

Where to get compost

The best composts are made from a variety of materials and are a good balance of carbon and nitrogen. Big box garden stores and local garden centers often sell bags of compost. Check the composition very carefully before you buy and read the labels. If you’re growing an organic garden, make sure any compost you purchase meets those standards. It’s usually more cost effective to buy compost in bulk, especially if you have a large garden.

Many commercial composts rely heavily on old animal manure, which can be a great help to garden soil. But make sure the manure has thoroughly broken down. Animal manure that is too fresh contains a lot of nitrogen, which can harm plants.

Make your own compost

If you don’t want the expense of buying compost, you can make your own. This is a win-win, since it also means less organic matter, cardboard, paper, and other compostables in the landfills. Making your own compost is, in my opinion, one of the best ways to cut expenses and reduce waste while also improving your garden.

I’m NOT a compost expert, so I’m going to include links to better sources for this – but here’s the basic idea.

Start with an outdoor compost bin or pile. Layer ‘green’ materials that are rich in nitrogen with ‘brown’ materials that are rich in carbon. Your greens are literal greens, like yard waste, as well as things like animal manure*, coffee grounds and food scraps **). Browns are cardboard, paper, wood shavings or dust, or dried leaves.

To ensure good breakdown, your pile should be mostly carbon items. That means you need four parts carbon to every part nitrogen. If the ratios are off, your compost will take longer to bread down, and might become smelly or slimy.

A few things you should know about making compost

• It takes a long time – months or even a year. So making your own won’t be an instant money saver. But the sooner you start, the sooner you’ll save.
• Getting enough browns can be challenging. Shred paper junk mail and ask friends or family to save their newspapers or cardboard for you.
• Compost needs some water – but not too much. Keep it moist but make sure it’s not constantly saturated.
• If you have a big garden, one pile probably won’t make enough compost for all your needs.
• You don’t have to buy a bin or a drum, but having your materials contained in a stack does help them break down faster.
• Make fertilizer by steeping finished compost in rain water for several weeks. Strain, dilute and water your hungry plants with it.

Set up a composting worm bin

Using red wigglers is a great way to turn food scraps and waste into compost in the form of worm castings. These are dense and rich and help retain moisture. You won’t get tons of castings unless you set up a mega worm bin but you can reap a LOT of benefits from a small amount of castings.

Here’s what you need to know about setting up a composting worm bin.

The best books about organic gardening and composting

I’ve touched on some concepts here but I’m not an expert on soil health, microbiomes or compost. If you want to dig deeply into these topics (and how you could you not?!), these are the books you need.

Click on any of the books to order your own copy through Bookshop. Buying from Bookshop means I receive an affiliate credit (at no cost to you), which helps cover the costs of producing content. Bookshop robustly supports local, independent bookstores.

Ways to Minimize Soil Amendments

There are a few low-cost ways to limit the amount or frequency of soil amendments your garden needs.

Crop rotation

If you can rotate your seasonal crops, you may not need to amend your soil as much. This is primarily useful in vegetable gardening, where a bed of tomato plants can leave soil stripped of nitrogen, calcium and other nutrients. If you follow a nitrogen-loving plant like tomatoes with a plant that helps restore nitrogen (like legumes), you can keep your soil balanced.

Cover crops

In larger garden beds, growing a quick crop of buckwheat, clover or even rye grass can restore depleted nutrients. These fast growing plants help nutrients re-form in the soil as they grow. Once they’re grown, they help in another way. Either chop the plants down and let them decompose on the surface or till them into the soil. Doing so adds organic matter into the soil, as well as more nutrients from the rotting plant parts.

Organic Matter Mulch

Covering garden soil with organic matter, like grass clippings, fallen leaves or aged, untreated wood mulch, has several benefits. A layer of mulch reduces weeds and keeps soil temperature more consistent, organic matter mulch can also release nutrients as it breaks down. If you regularly apply these materials to your soil, you may not need to amend with compost or other things as often, or at all.  In effect, mulching with organic materials is composting ‘in place’ rather than in a compost pile.

In the photo below, the herbs and flowers are mulched with grass trimmings. They keep weeds at bay and moisture in the soil while slowly breaking down to add organic matter and nutrients.

In combination, crop rotation, cover crops and organic matter mulch can do a lot to improve soil health, which can mean you don’t need to use soil amendments often. Crop rotation and organic matter mulch cost little to nothing, so they’re great ways to help your garden and your wallet. Seeds for cover crops are usually very inexpensive, so they’re also a budget-friendly option.

What if I don’t want to the expense of amendments, fertilizers or composts?

It is possible to have a thriving garden without the added expense of soil amendments, fertilizers, etc. How? Grow plants that are native to your region and, more importantly, well-suited to your specific garden. That means picking plants that will thrive in the conditions present in your garden. Look at the amount and timing of sunlight. Consider the soil texture. Notice if rainwater stands anywhere in the area. Is your yard shady or in full sun?

Take a good look at your growing space and make note of all of these things. Then measure how much growing space you have. Choose native plants that are the right shape and size for each area in which you’re going to plant. Got a soggy area? Choose native plants that thrive in damp or boggy conditions. Is one spot very sunny and often dry? Pick native plants that need dry heat and sun to grow.

A garden full of carefully selected native plants will thrive with very little care from you. They won’t need fertilizer or supplemental water (once established). Native plants are great at filling a space and holding their own against weeds. And they will offer support to native pollinators and birds, while improving soil and removing carbon from the air.

That sounds great. What’s the catch?

There are a few things to consider about a native plant garden. First, native plants tend to be prolific, especially in optimal growing conditions. They like to spread via rhizome in the ground or through seed heads, or both. They’re doing their job, which is to make more of themselves. That might mean that in the spring and fall, you need to spend a weekend removing volunteer plants or dividing mature plants into smaller plants. But honestly, that’s a pretty low time investment for a whole summer of low-maintenance flowers.

The other thing to consider is that in many places, native plants are viewed as ‘weeds’. Sometimes, it’s because of their prolific nature. They can spread in a way that is undesirable.  Other times it’s simply that garden companies have marketed native plants as ‘weeds” in an effort to encourage buying expensive, imported plants.

Your neighbors might look at a bed full of native plants and think you’ve simply stopped caring for your yard or garden because they only see ‘weeds’. The best way to avoid this is to choose plants that fit well into the space available. Avoid overly prolific varieties if you’re concerned about them taking over.  Use smaller, more compact plants and group plants of the same type together. A large bed of rudbeckia (Black-Eyed Susans)  is gorgeous and looks more deliberate than a bed filled with a dozen varieties.

And finally, a native plant garden doesn’t provide fruit and vegetables, at least not to the extent a standard food garden does. But it can be a nice way to have a beautiful, eco-friendly, low maintenance garden.

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