Natural Amendments and Fertilizers

The most beautiful plants are typically the result of wonderful soil. Among the best and least expensive ways to achieve rich, productive soil is to use natural amendments and to supplement your plants with a natural fertilizer when necessary.

A soil amendment is a substance used to improve the soil’s structure. As an added bonus, amendments help retain moisture and nutrients in the soil and fertilize plants. A fertilizer is meant to feed plants directly. If your soil is properly amended, you may find little need for fertilizers.

Using natural amendments and fertilizers over synthetic ones is beneficial for a few main reasons. With natural fertilizers, nutrients are released slowly and steadily, and the nutrients that do not get taken up by the plant help to enrich the soil and improve its texture, whereas a synthetic fertilizer is likely to quickly leach through the soil and find its way into our water and air supplies. Another major benefit of using natural amendments and fertilizers is that they enrich the community of living soil organisms, unlike synthetic ones, which tend to disrupt the community and compact soils. It is also of note that any fertilizer or amendment in too high a concentration can be harmful to – however, you are far less likely to burn your plants with natural dressings.

You’ll want to work any amendment into the top layer of soil using a shovel where possible. Take care not to turn the amendment too deeply in the soil; otherwise the nutrients will migrate south, out of the root systems’ reach. Alternatively, you can channel the amendment into rows. Create furrows that are about 12 to 14 centimetres deep, add your amendment of choice and plant directly on top so the root system can draw directly from the good stuff below. If your garden is established apply the same concept, but dig the furrows between plants.

Here are a few excellent natural amendments to try:

Compost or worm castings ensure that nutrients are slowly and gently released into the soil. These amendments are top in terms nutrients and improving soil quality and texture.

Manure is another great amendment choice. It is easy to use and provides a well-rounded source of nutrients. If you’re getting manure from a local farmer, be sure to ask if it is well aged, as fresh manure is nutrient rich making it too harsh for plants. If the manure is fresh avoid applying it to plants straight away, this especially applies to manures that break down quickly like sheep or chicken waste.

Green manure involves growing a nutrient-rich crop plant and working it into the soil once the leaves have matured but before the plant goes to seed. This process returns nutrients to the soil and helps improve the soil’s texture. Green manure, also called cover crops, is especially wonderful for vegetable gardens or for conditioning soil before establishing any garden. Clover, wheat, rye, fava beans and vetch are all popular choices for cover crops.

Seaweed is a great soil conditioner; it is comparable in nutrient content to cow manure and is rich in potash. Seaweed should be worked into the soil (it can become sticky if left on the surface) or added to your compost pile. If you do not have access to the fresh stuff, you can purchase it as seaweed meal or calcified seaweed.

Leaf mould consists of partly composted leaves. It can be used as a mulch or worked into the top layer of soil to improve texture and humus content. It is very effective at holding moisture. Making leaf mould with a black plastic garbage bag is easy. Just poke a number of holes in the side of the bag and pack in the leaves; add water if the leaves are dry and again if they become very dry throughout the summer. You’ll have a finished product in one to three years, depending on what type of leaves you use.

With the exception of liquid fertilizers and any specific directions discussed below, the following fertilizers can be broadcasted over the soil. This means you evenly spread them across the bed and mix them into the top 10 to15 centimetres of soil. Broadcasting is best done before planting in early spring. For established beds, these fertilizers can be applied as a side-dressing, worked into the top few centimetres where possible.

Try any of these natural fertilizers to suit your needs:

“Black tea” liquid fertilizer, also known as manure tea or compost tea, is a great
nutrient-rich way to water your plants. Simply add any kind of manure or compost to a bucket of water and let it sit for a day. Strain out the solids, and you will be left with a brew that will make things grow. There is no need to be precise, but generally you can use about 1.5 kilograms of manure in 20 litres of water. Dilute this until it is much lighter in colour, like a weak cup of tea. Use the tea to water soil near the base of plants and avoid pouring it directly on foliage and stems.

Fish emulsion liquid fertilizer is a good source of nitrogen, phosphorus and other nutrients needed in trace amounts. It is a reasonable all-round fertilizer, though it lacks calcium. If you have fish scraps and a large property, take the scraps and add them to a screen-covered bucket of water.  Assign this to a far corner of your yard to sit for two or three months, beware that it will be quite smelly! A layer of oil will form over the water and the rest will sink to the bottom. Harvest the oil and store it in a container with a tight lid. To water with this, Marjorie Harris proposes a mix of ONE cup of oil to about 20 litres of water.

Blood meal is good source of fast-acting nitrogen that will not add bulk to your soil.

Hoof and horn meal are high in nitrogen and do not readily burn plant roots since they are slow releasing. For best results, mix these with sawdust, which binds nitrogen.

Bonemeal is a great source of slow-acting phosphates and of nitrogen too; however, you’ll want to consider that dogs may find the bonemeal enticing and may dig up your beds.

Fish meal is a slow-acting nitrogen source. It also supplies phosphorus, calcium and other micro-nutrients. Bury this fertilizer several centimetres into the soil so it will not be dug up by clever animals like skunks or your pets. You can even try burying your meat and fish scraps near mature plants, but again, be sure to dig fairly deep so animals are not lured by an easy meal.

Oyster and bivalve shells are made of calcium carbonate which is strongly alkaline and can be used to neutralize an acidic soil. Some garden centres sell ground oyster shells but you can use anything left over from your dinner. Bury rinsed (to remove excess salt), crushed shells of crab, lobster, oysters, etc. in a marked spot in your garden. They will decompose after about three weeks, at which point you can dig the spot up and spread the broken shells around.

Alfalfa meal is simply ground-up alfalfa that provides nitrogen and releases some phosphorus and potassium as well. It also has a plant hormone that may increase growth.

Soybean meal is best used on acidic soils to feed plants nitrogen. It is slow acting and lasts all season, but take care not to overuse it as it can cause root burn, overstimulate growth and emit a foul smell.

Wood ashes from fireplaces and woodstoves contain calcium carbonate which is great for neutralizing an acidic soil; they also provide a source of phosphates and potash. You’ll want to be sure that no garbage was burned in your ash supply. Wood ashes are best applied to sandy soils. Avoid using them on clay soils, germinating seedlings and plants that thrive in acidic soils.

Rock or mineral fertilizers are great at providing many trace elements but it is best to also include some organic matter with nitrogen for a more well-rounded fertilizer. The greatest advantage to applying rock fertilizers is that they have staying power, lasting from five to 10 years.  You can typically find these at garden centres. Here are a few examples:

•    Phosphate rock is recommended for a soil severely depleted in phosphates. It slowly releases phosphate, as well as boron, zinc and nickel all needed in tiny amounts for plant health. Rock phosphate should be used sparingly. Follow the package recommendations as to not disrupt the soil’s microbial community and create a build-up of salts.

•    Granite dust is a wonderful source of potash and also has some trace elements. Its chief advantage is that it won’t affect the pH of the soil.

•    Potash rock contains potassium and many other trace minerals. Apply it right on the soil with some organic materials, any fruit or vegetable scraps you might add to your compost will do the job.

For soils lacking in calcium with no need for pH alteration, try gypsum. Gypsum is calcium sulphate, so some sulphur will be added to the soil as well. It can also improve the aeration of clay soils.

Calcitic or dolomitic limestone can alter the pH of an acidic soil, owing to its calcium carbonate content. Use limestone if you need to sweeten your soil (make it more alkaline).

Sulphur is used to increase the soil’s acidity; however it may not be of any use on very alkaline soils. It takes about three weeks in the soil for the sulphur to be converted into a useable form. It must be converted to sulphuric acid by soil organisms for plant uptake. For best results, add some compost to help the process along.

Epsom salts are ideal if your soil is lacking magnesium and sulphur. If this is the case, give seeds a germination boost by sprinkling about a cup of salt over a nine square-metre area before planting. For established plants, water with a mixture of 30 grams of the salt to about four litres of water, once a month or more. At this application rate, there is no need to worry about build-up in the soil.