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What Are Soil Amendments and How Should You Use Them in Your Garden?

Gardening can seem very complex at times, especially when you’re just getting started, and it takes a little time and education to better understand the system you’re dealing with to get the best overall results. One aspect that you shouldn’t overlook is the benefit of adding soil amendments to your garden. But what exactly are soil amendments, why are they important to your garden’s overall health, which ones do you need and how do you use them in your garden? In this article, we’ll go over the basics of soil amendments, giving you details on what, why, which ones and how to help you get started with these gardening powerhouses.

What Are Soil Amendments?

Soil amendments are materials that are added to your soil to improve certain characteristics and help boost your yields. In traditional gardening, they can be turned into the soil, but in no-till systems, they deliver a wide range of benefits for your garden through a range of application options, boosting nutrition and soil factors that improve your garden’s overall performance. By adding these materials to your garden, you’ll quickly see improved results, whether through yields, better soil performance or reduced pest issues.

Soil amendments can include minerals such as limestone and calphos, animal processing by-products such as fish meal or oyster shell, beneficial living microbes such as bacteria or mycorrhizae, natural botanical materials such as biochar and willow bark, specific types of soils such as clay and greensand and a wide range of other materials. By adding these materials to your soil, you can reduce pests, improve the soil’s ability to hold nutrients and moisture, change the soil pH, improve microbial action and other benefits that make it much easier to get the best possible results out of your garden.

There are a wide range of available soil amendments, so in this article we’ll go through some of the major categories of soil amendments along with some specific amendments in each category and their uses. This will help introduce you to the world of soil amendments and increase your knowledge of which amendments are the best option for your current gardening needs. Some amendments help the soil hold nutrients, some will deliver nutrients for the plants, others will have an impact on life in your soil, either benefiting beneficial insects and microbial life or slowing down pests such as weeds and harmful insects.

Examples of Soil Amendments

Soil amendments can achieve a wide range of end goals. In this list, we’ve broken down some common purposes for amending soil and included some common examples of soil amendments that can be used in those categories. However, many of these soil amendments have purposes that work across multiple categories, such as providing water- and nutrient-retaining capability, delivering micronutrients and providing a friendly habitat for microbial life in the soil. This is a common issue faced when working with organic soil amendments, but this multi-faceted aspect also means that each compound simply provides that much more to your garden’s overall health.

Improving Nutrient-Holding Capacity

Consider the common story about the college professor who shows his students a jar full of rocks and then asks if it’s full, then adds sand and water to completely fill the container in stages. The rocks represent sand, the largest soil particles, while the sand represents clay and organic matter. The clay and organic matter can fit into the small spaces between the large sand particles and the larger ratio of surface area makes the larger number of these tiny particles much more reactive in the soil while allowing them to retain more nutrients and water for the plants you’re growing.

In soil science, the higher surface ratio of the clay and organic matter can increase the soil’s cation exchange capacity (CEC), or in simple terms, its ability to retain nutrients. This is based on chemistry, where the higher the ratio of surface area of a particle, the more active it is in a reaction. The smaller the size of the particle, the more surface area it has compared to its mass. Because the particles are smaller, they do more for your plants and the health of your garden.

The higher the CEC, the more nutrients the soil can hold on to and keep available for your plants, creating a deeper reserve of nutrients. Instead of having the nutrients and moisture quickly wash out of the soil, such as may happen with sandy soils, clay particles such as bentonite clay help hold both nutrients and moisture, improving the soil’s ability to grow plants successfully. Having a higher CEC in your soil makes it easier to maintain your garden because you’re not having to constantly adjust soil nutrient levels – the nutrients your plants need are already there, being held by the existing soil.

However, the real magic happens when you add organic matter to your soil, because organic matter is exponentially higher in its CEC capability while delivering other benefits. As a few examples, willow bark can also improve rooting, alfalfa meal also boosts macronutrients, powdered aloe also helps hold moisture and improves many plant’s ability to take up nutrients, cottonseed hulls can also act as a natural mulch, rice hulls also add air to the root zone of the soil by improving aeration and biochar chips add habitat for friendly soil microbes.
Improving Soil Nutrition

There are a wide range of available soil amendments that help boost soil and plant performance. To boost your macronutrients, especially nitrogen, phosphorous and potassium (NPK), you’ll get great results from fish meal for nitrogen with some phosphorous, feather meal for heavy nitrogen feeders such as corn, cottonseed meal for nitrogen and phosphorus with some potassium, fish bone meal for phosphorus with some nitrogen, blood meal for fast-uptake of high nitrogen levels and seabird guano for high phosphorus levels in budding and flowering.

However, NPK aren’t the only nutrients you’ll need to watch – there are a number of micronutrients and lower-level micronutrients that are not needed in as high of quantity, but are still just as critical to your garden’s well being. Calphos has phosphate, calcium and trace minerals, langbeinite has potassium, magnesium and sulfurs with a neutral pH, greensand contains potassium, iron, magnesium, silica and trace minerals in a slow-release format, granular azomite has a range of beneficial minerals and trace elements while improving root systems and overall garden quality while powdered amozite delivers the same actions in a faster fashion, kelp meal provides a range of micronutrients and plant growth benefits for vegan gardeners, yarrow flowers add high amounts of sulfur, potassium, copper, phosphate and nitrates, stinging nettle leaf adds NPK as well as copper, iron, zinc, magnesium and calcium, and worm castings add NPK, calcium and magnesium. Basalt rock dust not only has a range of trace minerals, it’s also a nutritional powerhouse that improves the availability of other nutrients already in the soil while improving drought tolerance.

Changing Soil pH

For the most part, soils that are under cultivation tend to become acidic over time, so adding material to alkalize the soil, raising the pH, can make a big difference in your garden’s performance. This is important because when the soil pH gets too acidic, it can impact the availability of certain nutrients and cause your plants to fail. Though the same is true is soil becomes to alkaline, typically acidity is the issue that is faced in gardening. Fortunately, Mother Nature gives us a wide range of materials to help with these issues.

For a slow, natural material that slowly adds organic calcium and improves aeration in the soil, crushed oyster shells work extremely well. For a quick boost of calcium that also adds silica, horsetail grass does a great job. When you just need a quick boost of calcium for your tomatoes or other nightshades, the instantly-available calcium in hydrated lime is a great way to turn blossom-end rot around in your crop. Oyster shell flour also works well due to the smaller particle size releasing calcium faster, but with organic calcium forms instead of inorganic mineral. Agricultural gypsum adjusts pH while helping with sodic and compacted soils, erosion and runoff issues.

Improving Microbial Action

Microbes can make a huge difference in your garden’s performance, so it’s important to create an environment that keeps beneficial microbes flourishing in your garden. You can manage this in a range of different ways, by adding more microbes to your soil, adding habitat for them or adding material that helps feed them and keep them reproducing across your garden.

You can actually add mycorrhizal fungi directly to your soil, which essentially expands your plants root zones to help them take up more nitrogen and other nutrients. Crustacean meal is awesome for your beneficial insects and soil microbes while boosting calcium, nitrogen, phosphorus and chitin in your soil. Dried molasses can be top-dressed to feed your soil microbes and keep them flourishing. Biodiverse compost adds to your soil’s fungal activity while adding nutrition to the soil.

Reducing Pests

What if what you add to your soil can make your pest control tasks easier later in the gardening year? Many soil amendments do just that. Corn gluten meal can be used to prevent weed growth early in the season when it’s top-dressed onto your garden, preventing the weeds from emerging in the first place.
But what about insect pests? Diatomaceous earth is made from fossilized skeletal remains of aquatic organisms, and in addition to boosting silica, it can deter or reduce pests because of the abrasive nature of the amendment. Neem seed meal is a powerhouse that not only combats fungus gnats, root aphids and other pests, it also increases organic matter and boosts your soil microbe population while releasing macro and micro nutrients.

How Should You Use Soil Amendments in Your Garden?

Once you’ve decided what kind of amendments you need in your garden, how do you use them? For no-till gardens, you can add most amendments as a top dressing, while others work well as a foliar spray. Top dressing are simply spread on top of the soil surface and allowed to spread down into the soil with irrigation or rain water, while foliar sprays are applied to the leaves in an aqueous form to be absorbed through the leaves and transported throughout the plant. Some amendments also work well as teas, where they are brewed and the resulting tea is then watered into the garden once the tea cools. Others are simply allowed to sit in water and release their nutrients, beneficial compounds and similar properties into the water rather than heating them, especially those that work with beneficial microbes.

One aspect to consider is particle size. Basic chemistry teaches us that a larger particles has a lower percentage of available surface area, while smaller particles have a larger percentage of available surface area. This means that smaller particles tend to act much more quickly when compared to larger particles. Consider powdered sugar versus rock sugar, where both will dissolve in water eventually, but the powdered form dissolves much more quickly. If you want something to act quickly in your garden, go with a smaller particle size; if you want it to act more slowly, such as across an entire growing season, choose larger particles.

By having a better understanding of what soil amendments can do for your garden, you can make smarter decisions about which amendments to use at what times and for what purposes. Take a little time to learn a bit about a few of these amendments and your garden will benefit greatly. If you’re ready to take your gardening to the next level while reducing your overall work, the experienced professionals at Redbud Soil Company are ready to help. Please feel free to reach out today to learn more, to get more information or to place an order for some of our exceptional soil amendments and other garden products.

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