Soil

Product inputs

There are many components that go into creating the right environment for soil organisms and plants. When striving for well-balanced soil, we need to consider both the nutrient content and physical structure of the soil.

There is no one magic ingredient that can be added to create good growing conditions- all of the products available improve one or more aspects of the soil, and can be used in combination to make the soil healthy.

All of these inputs, with the exception of mulch, can be added when the beds are being prepared for the next crops, mixing them through the soil.

Fish emulsion, seaweed products and sea minerals can be used as foliar sprays at any time to give the plants a boost.

 

Animal manures

Animal manures are excellent for improving soil structure, adding humus as they break down, holding moisture, and improving soil microbiology.

Animal manures need to be composted and are generally combined with hay, straw or similar materials. The manures provide the nitrogen content and the hay etc. provide the carbon content needed in composting, but they can be left to compost on their own. Raw manures are far too strong and will burn the plants when applied directly onto the garden. They may also contain pathogens that need to be destroyed by biological processes. It is particularly important to compost chicken manure for two to three months before use.

Manures are available commercially that have already been composted. If you buy uncomposted manures, they can be used in your own compost or with green manure crops, but must definitely have time to compost before being planted into.

Liquid compost fertilizer

Liquid fertilisers can be easily made from composted animal manure. They are very effective and good for correcting micronutrient deficiencies in the soil.

To make liquid fertiliser from animal manure

Use roughly 1 part manure to 10 parts water. For example, we would often use a 2 litre ice-cream container of manure and a 20 litre bucket of water.

Place the manure in a hessian bag (or something similar so the water can filter through), and suspend it in the water like a tea bag for about 3 weeks, dunking it along the way as you would with a tea bag. This brew should then be diluted 1 part liquid to 10 parts water.

It is better to apply a weak solution often rather than a strong one occasionally.

Other liquid fertilisers, such as fish emulsion and seaweed meal, can be added to the liquid manure “tea" when spraying out on plants to provide a good all-round fetiliser.

Liquid manures, especially those made from incompletely composted manure, can contain pathogens that could be dangerous to humans if ingested. They should only be applied to the soil and not over the leaves of food crops.

Returning crop residue, like these lettuce leaves, back to the soil will help maintain organic matter levels

There is no one magic ingredient that can be added to create good growing conditions.

all of the products available improve one or more aspects of the soil, and can be used in combination to make the soil healthy.

Input Types

Chicken manure

Properties

  • very high in nutrients, particularly nitrogen and phosphorus as well as 11 other essential nutrients. Chickens are often fed mineral supplements, including calcium, which make their way into the manure
  • slow release fertiliser
  • calcium in it helps to break up clay soils
  • doesn’t contain any organic matter

Availability

Available as dried pellets or in bulk

Comments

Bird manures are richer fertilisers because they contain urea

Cow manure

Properties

  • will add nutrients but not a lot since cows only eat grass, which is low in nutrients
  • excellent bulk source of good-quality organic matter which will improve the overall condition of the soil

Availability

Farmers sometimes sell straight from the paddock.

Already composted and sold in bags from garden supply stores.

Comments

It can also be used on Australian native plants that are phosphorus sensitive.

Horse manure

Properties

  • more nutrients than cow manure as horses are often given other feed to supplement their grass diet: such as cereal grains and commercial mixes with added vitamins and minerals 
  • good source of nitrogen

Availability

Many horse owners bag it up and sell it at the farm gate

Comments

Usually contains more seeds than other manures

Check with the horse owners as to what additives they give their horses as this can vary with the needs of the horses. Race horses would need high protein feed whereas a paddock horse may just be given lucerne and molasses.

This won’t affect the quality of the manure once it is composted; it will just vary a little in composition.

Sheep manure

Properties

  • much the same as cow manure as both are grass eaters
  • relatively low in nitrogen, but high in phosphorous and potassium
  • the droppings of sheep are hard pellets which makes them a slow release fertilizer

Availability

Usually from the paddock or sold composted in bags

Alpaca manure

Properties

  • will improve soil texture and water-holding capacity
  • high in nitrogen and potassium
  • relatively low in phosphorus
  • moderate calcium and magnesium content
  • relatively low in organic content due to the animals efficient digestive system
  • makes an excellent soil conditioner

Availability

It's not easy to get hold of; we found an alpaca farm and collected it from the paddock ourselves.

Comments

It is able to be spread directly onto soil without burning the plants. Although their poo is in pellet form we found that if left for a while it all clumps together. By mixing it with a bulking medium (compost will do) it will improve its porosity as it is too dense and heavy to allow air flow.   

I prefer to compost it, just to be sure that it will break down and that there aren’t any pathogens contained in it.     

Bentonite clay

What is it?

  • an impure clay formed by the weathering of volcanic ash by water
  • different types of bentonite clays are categorised by the main element they contain e.g. sodium bentonite, potassium bentonite, calcium bentonite.

Properties

  • has the ability to absorb a great deal of water and is used as a ‘wetting agent’
  • has a very high capacity to store nutrients (highly colloidal)

Comments

Calcium bentonite is the bentonite clay used in gardens, as it is more stable and holds and releases water more effectively than the other clays

Its water and nutrient holding capacity make it a particularly good additive for sandy soils

Biochar

What is it?

  • fine-grained, highly porous charcoal produced by the controlled heating of organic matter at high temperatures in a low oxygen environment

What does it do?

Increases soil fertility

  • it is more effective in retaining most nutrients and keeping them available for plants than other organic matter i.e. good cation exchanged capacity
  • soils with the addition of biochar are typically more fertile, resulting in higher yields and better quality produce for longer periods of time.
  • improves almost any soil, but areas with low rainfall or nutrient poor soils benefit the most.
  • reduces the leaching of nitrogen into ground water
  • retains phosphorus which is not retained by other organic matter
  • sequesters carbon and helps soil retain nutrients and water, thereby improving soil fertility
  • believed to enhance soil quality by increasing its microbial content
  • improves yields while reducing water and fertiliser requirements.
  • acts like a filtration agent in water
  • possibly reduces the emission of nitrous oxide, a contributing component of greenhouse gases. Nitrous oxide is produced by microbes converting excess nitrogen through nitrificaction (in aerobic conditions) and denitrification (in anaerobic conditions). Whilst animal manures are a source of nitrogen, increased use of synthetic or inorganic nitrogen fertilisers has been a major contributing factor.  

Improves soil structure

  • lowers the density of clay soils, increasing aeration and root penetration, whilst in sandy soils it helps retain water and nutrients.
  • moderates soil acidity and can partially offset the acidity of nitrogen fertilizers.
  • does not break down easily which means it can continue to have a beneficial effect for a long time.

Comments

It was developed after the discovery of the Terra Preta (Black Earth) soils in the Amazon basin, which are the result of the common practice by the Amazonians of cover burning vegetation with soil.

Blood and bone

What is it?

  • an animal by-product

What does it do?

  • the blood meal contains a small amount of slow-release nitrogen, and the bone meal slowly releases calcium and phosphorus which are important for the development of roots, flowers, fruit and seeds

Availability

Sold as a dry powder from garden supply stores.

Comments

It does not contain potassium

Coir peat

What is it?

  • by-product from the coconut industry

Properties

  • retains moisture
  • aerates the soil

Comment

It is a good substitute for peat moss in potting and propagating mixes

It is very acidic so  the pH of the soil will be lowered.

Feathers / fur / hair

What is it?

  • bird feathers and hair from humans or animals

Properties

  • these are quite high in nitrogen

Availability

  • contents from the vacuum cleaner, or you could ask a local hairdresser for their clippings

Comments

Good to add to the compost. In the proper process of decomposition any chemical residue will be rendered inert.

Compost

What is it?

  • “compost” is the product of the decomposition of organic matter through biological activity

What does it do

  • will condition the soil by improving structure and fertility.
  • increases organic matter and nutrient levels
  • does not have high levels of nutrients, but those that are in it will not leach out easily and will be available to plants.
  • has a high cation exchange capacity
  • improves water-holding ability of soil
  • increases biological activity and humus levels
  • less loss of nutrients, especially soluble nitrogen, through leaching and evaporation
  • usually has a good range of trace elements, which inorganic fertilizers lack
  • prevents the soil surface from crusting
  • helps form soil aggregates in poorly structured soils
  • reduces the incidence  of soil erosion
  • keeps soil cooler in summer and warmer in winter
  • increases soil aeration which helps promote root growth
  • in heavy clay soils, compost can help loosen and aerate the soil, thereby breaking up the clay
  • improves the drainage of the top soil

Comments

During the composting process it is important that sufficient heat is generated and aeration maintained so that many impurities will be broken down and undesirable microorganisms and foreign seeds (including weeds) will be killed. It takes at least three months for complete decomposition and that is if everything is done properly.

Making your own compost is ideal as you will then know exactly what is going into it. Unfortunately this is not always practical and it is difficult to make enough as well as the time factor involved. It is important to get a good quality compost.

Compost is ready when there are no recognizable bits of the original materials; it is fine-to-crumbly in structure; almost black in colour, and; has a good ‘earthy’ smell.

Compost can be used to make a compost tea, which can be used as a soil drench or as a foliar spray.  By spraying onto the plant it works faster as it applies micro-organisms and nutrients directly on the plant. A tea will spread the benefits of compost further which is good if compost is not readily available. To give an extra boost add sea minerals, seaweed and fish emulsion (all or any one) can be added to the tea.

Teas can be made using a large bucket or drum. Put some compost into a bag, shade cloth or a hessian bag is ideal, and placing it in the bucket. Cover with water and let it steep for two to three days or up to a week stirring it fairly often. Another option is to use a small air pump to aerate the mixture as it is brewing. The ratio of compost to water is 1 part compost to 10 parts water.1 Dilute 1-4.

Mushroom compost

I am undecided about this. Some sources say it is a great fertilizer and soil conditioner; others say it is ‘spent’ and doesn’t have much nutrient value left. It is valuable as bulk organic matter as it is made up of hay, straw, corn cobs, poultry and horse manure, cocoa shells, peat moss and other organic material. My concern is about what is added by the mushroom farmer in the way of chemicals to combat the pest and fungal problems they encounter. Perhaps putting it in the compost and have it go through the process again will eliminate those concerns.

Effective micro-organisms (EM)

What is it?

  • a combination of naturally-occurring live beneficial micro-organisms such as yeast, lactic acid bacteria which produce lactic acid from the fermentation of carbohydrates (they are probiotics) and photosynthetic bacteria which convert light energy into sugar.

    This mix combines both aerobic and anaerobic micro-organisms which co-exist and are mutually beneficial within the soil environment.

What does it do?

  • these micro-organisms create an environment which produces strong anti-oxidant growth which in turn encourages other beneficial organisms
  • produce sugars and bioactive substances such as enzymes, vitamins, amino acids and antioxidants.
  • possess constructive and regenerative properties.
  • accelerate the decompose organic matter- can be added to your compost heap
  • play a positive role in plant quality as well as soil fertility and the prevention of disease.       

Availability

Purchased as a liquid culture.

Comments

Over time, the amount of fertilizers required will decrease and weeds will be reduced.

Weeds and diseases are suppressed as  Em makes the environment more compatible with beneficial organisms and less sustainable for pests and pathogens.

Fertility improves because the increased biology produces better soil aggregation (the binding of soil particles into larger clumps called peds) which in turn creates better drainage, aeration and ability to hold nutrients.

These micro-organisms are present in soil but can be easily depleted by adverse soil conditions. Adding this premix provides a much greater concentration of specific microorganisms that will bring about changes in the environment suitable for the other beneficial organisms to thrive in, eventually out competing the nasties and increasing their own populations. When applying EM it is important to also incorporate a feed for the bacteria. This is usually a molasses based product and often supplied with the culture.

  As these organisms work well in anaerobic conditions, they are particularly effective in areas that are muddy and boggy or where there is putrefaction.

Fish emulsion

What is it?

  • a liquid fertilser produced from the remains of fish that have been processed for fish oil and fish meal

Properties

  • high in nitrogen but also contains soluble phosphorus and potassium in a form immediately available to the plant
  • also contains insoluble forms of phosphorus and potassium which the soil micro-organisms will break down over time into a form which plants can take up.
  • promotes healthy roots, buds and flowers
  • effective on downy mildew
  • can be used in conjunction with liquid kelp to give an extra boost to the plants

 

Comments

It has an immediate as well as a slow release effect. Fish emulsion and kelp work well together as a good tonic for plants.

Fish meal

What is it?

  • ground up fish remains

Properties

  • good source of nitrogen, nutrients and minerals
  • slow release
  • promotes plant growth
  • soil conditioner

Application

Mix with water as a foliar spray or add to the soil

Fulvic acid

What is it?

  • it is a humic acid  produced by the breaking down of organic matter by bacteria and fungi. It does not undergo any  further biological breakdown.

What does it do?

  • stimulates microbial activity
  • food source for worms
  • excellent soil conditioner

Availability:

Compost will have humic acids but fulvic acid can be purchased on its own in liquid form.

Comments:

After mulching we would give the mulch a water with a solution of fulvic acid to stimulate microbial activity in the mulch.

It easily depleted by agricultural practices and by leaching, thus it is important to add these acids back to the soil in the form of compost or as a supplement.

Fulvic acid (applied as a liquid) has a small molecular size, giving it the ability to diffuse easily though membranes (which enables it to penetrate plant leaves), as well as a higher oxygen content than other humic acids. It is soluble in water, making it an excellent foliar spray and root drench, but it is used up quickly.

Green manures

What is it?

  • plants grown in the beds after crop harvesting as part of soil preparation for the next round of planting. They are left to grow to the flowering stage then cut down and turned back into the soil.

What does it do

  • grasses are able to retrieve potassium from the soil and can utilize excess nitrogen
  • herbs such as chicory and comfrey are high in essential elements and have deep roots that are capable of bringing up nutrients which would be out of reach for most crops.
  • legumes such as vetch, beans, lupins, clover and lucerne can add large amounts of nitrogen to the soil.
  • protect the soil from erosion
  • retain nutrients by stopping them from leaching out
  • cycles nutrients from lower soil layers to the upper layers
  • suppress weeds
  • will add  organic matter

Comments:

They can also be planted amongst permanent crops, as in orchards; needs to be regularly cut to ensure the continued release of nutrients.

Clippings can be collected for compost or for use as mulch around other plants, or even left to breakdown where they have grown.

Annuals such as rye grass, oats, lupins, vetch and field peas, which die down or are slashed to form mulch, can be used as part of a rotation system with crops. Clover is a very good green manure crop.

Often the seeds of green manure crops will be “inoculated” with beneficial fungi (VAM) when they are purchased.

Green sand

What is it?

  •  mineral deposits that were once part of the ocean floor, giving it a greenish colour

Properties

  • made up of iron potassium silicate (glauconite), so is a near-pure form of potassium.

Comment

It is difficult to find products that contain only potassium as many have other elements that may already be in sufficient quantities in the soil.

Guano

What is it?

  • fossilized seabird droppings

Properties

  • it contains soluble and slow release phosphate as well as calcium and trace elements
  • has natural fungicidal properties
  • great soil builder and compost activator

Availability

Available as a powder.

Comments

It does not contain cadmium like chemically treated commercial phosphates.

It is safe for use on all fruit trees, herbs, vegetables and ornamental plants.

Gypsum

What is it?

  • it is a naturally occurring, hydrated calcium sulfate.

What does it do?

  • will improve clay soils, although not all clays will respond to it.

  • will add calcium to the soil without raising the pH as liming products do.

Comments:

To test whether the soil will respond: add some clay and gypsum to a glass of water and leave it overnight; if the water becomes cloudy the gypsum has been able to disperse the clay and will work in the soil. If not, the clay will settle to the bottom.

Gypsum is good for soils with a lot of sodium in them as the calcium displaces the sodium. It will not affect the pH of the soil.

Humic acid

What is it?

  • a mixture of many different acids produced after bacteria and fungi have broken down organic matter.

What does it do

  • creates humic colloids (see cation exchange capacity), thereby keeping nutrients in the soil and making them easily available to plants
  • excellent soil conditioner
  • does not undergo further biodegradation.

Availability:

Compost contains humic acids but it is available in concentrated, slow releasing granules

Comments

Naturally occurring humic acids are easily depleted and leached out of the soil with agricultural practices, so it is important to add them back in the form of compost or as a supplement in order to stimulate microbes and provide food for worms.

Humus

What is it?

  • organic matter that has been completely broken down and cannot decompose any further. It is the material left after all the micro-organisms and plants have finished using up whatever bits they wanted.

  • usually found in the topsoil. It is dark brown or black in colour.

Properties

  • has no nutrient value as it is completely decomposed but has a high cation exchange level which actually means that it can store the nutients. 
  • good to add to sandy soils as they are not colloidal i.e. they have no cation exchange capacity (poor nutrient-holding ability)
  • good water holding capacity- again excellent for sandy soils which drain too quickly
  • acts like a glue for binding soil particles together, thus improving soil structure and aggregation, especially if the soil has a tendency to ‘crumb’
  • conserves soils by preventing erosion
  • generally improves the movement of air and water through the soil.

Comments

When compost or organic matter is continually added to the garden, humus levels will gradually increase.

Compost, by comparison, is still breaking down and contains nutrients, fungi, bacteria and microorganisms. Compost will eventually become humus.

Kelp

What is it?

  • type of seaweed; specifically a large brown algae, although it can vary in colour.

Properties

  • although it is not high in nitrogen and phosphorus it has a reasonable amount of potassium.
  • has an amazing amount of trace elements, growth hormones, enzymes, fungal food and disease-fighting properties
  • will help in correcting deficiencies in micronutrients
  • helps to control downy mildew
  • use in conjunction with fish emulsion to give plants an added boost.

Availability

As ground seaweed, seaweed meal and pure liquid seaweed or fresh kelp

Comments

Good to combine it with a high nitrogen fertilizer, such as fish emulsion, to create a complete fertiliser

Liquid seaweed is good to use because it is difficult to overdose the plants

Fresh seaweed is excellent in compost as it breaks down quickly, but all traces of salt must be washed off before it can be added.

TIP- We would give our seedlings a dip in seaweed solution just prior to planting out as it seemed to reduce transplant stress. Immerse the roots in the solution, either by letting the seedling tray sit in the solution or giving them a quick dunk when planting (trying not to lose too much soil from around the roots).

Lime

What is it?

  • crushed limestone

What does it do

  • adds calcium carbonate to the soil
  • increases the pH of the soil making it less acidic

The main types of lime used in agriculture are:

Agricultural Lime   (most commonly used)- contains 35% to 38% calcium with very little magnesium 

  •  raises the soil pH (i.e. makes it more alkaline)
  • not desirable to use it around plants that like an acidic soil

Limestone (pure calcium carbonate)- contains 40% calcium and no magnesium.

  • raises the soil pH (i.e. makes it more alkaline)
  • finely ground calcite limestone acts as a slow release form

Dolomite - contains    12% to 20% calcium and 8% to 11% magnesium

  • raises the soil pH (i.e. makes it more alkaline)
  • is an untreated limestone rock that also contains magnesium  

Comments

Lime is used to regulate the pH of acidic soils. In this sense it is often said to "sweeten" the soil. The more acid a soil, the more hydrogen ions in the soil. The carbonate component of lime converts  these hydrogen ions to water and carbon dioxide thereby neutralising the acid.

Lime can also be used to break up clay soils. It has the effect of making the soil particles stick together in small clumps rather than in one big impenetrable or gluggy mass. Because limes are all rocks and not very soluble, they will take time to work.

The finer the lime granules, the quicker the lime will react with the soil

 

Molasses (blackstrap)

What is it?

  • it is the by-product of cane juice after it has been boiled for the third time. It contains a small amount of sugar.

Properties

  • the sugar content will feed bacteria and micro-organisms.
  • contains small amounts of vitamins and significant amounts of some minerals including calcium, magnesium, potassium and iron
  • it is a chelate, meaning it is able to convert nutrients into a form that makes them available to microbes and plants.

Comments

Use the unsulphured blackstrap variety made from ripened cane that has not been treated with sulfur dioxide and has less sugar content.

Add to other “teas” and milk as a foliar spray, or into your compost.

The general concentration is 50 ml of molasses to 4 litres of liquid, either water or other fertilizers.

Mulch

What is it?

  • is any material spread over the soil and around plants

What does it do:

Generally mulch is some form of organic matter although technically pebbles and gravel can be used as mulches.

Organic mulches have the added properties as follows.

  • a layer of mulch over the soil will keep the soil cooler
  • retains moisture and reduces moisture evaporation out of the soil
  • stops the soil from crusting in hot, dry weather
  • suppresses weeds
  • provides food for soil fungi and micro-organisms 
  • will break down into soil

Some of the forms of mulch are

Wood chips - better for ornamental gardens as it is slow to break down , create a fungal dominant soil and may come from trees which have a toxic effect on vegetables.

Shredded leaves- greener leaves have more nitrogen but are also wetter, so can clump and become slimy. Dried out a little they will still provide some nitrogen, and mostly add carbon and minerals.

Grass clippings- the greener the grass the more nitrogen it contains but, like leaves, if it is too green it will mat and become wet. A light layer will allow it to dry out a bit and it will return nitrogen to the soil.We use our own grass mulch from paddocks that have been slashed but we let it dry out for a few days before using it. 

Pine needles- will not make soil significantly more acidic, but are my choice of mulch around acid-loving plants.

Straw and hay– chopped stalks of grain plants. This type of mulch is often cut in longer stringier pieces which makes it difficult to get a good covering over the soil.   
- adds organic matter when it breaks down.
- should be dried out so that weed seeds are killed, especially hay collected from pastures
- mostly carbon as the nitrogen is lost very quickly as grass dries

Pea straw- is high in nitrogen but it does break down quickly  

Alfalfa - one of the best mulches available because the plant has deep roots when growing, giving it access to lots of nutrients. It is like a complete fertilizer and is particularly high in nitrogen.

Lucerne - has a higher level of nitrogen and can be used when fairly fresh. It has a high protein content and often fed to livestock. It is usually quite expensive.

Bamboo – has a high level of silica. Leaf litter is good for mulching and composting. It needs to be broken up finely to make decomposition easier.

Sugar cane – finely shredded sugar cane is rich in nutrients and decomposes at a fairly slow rate.

Comments:

All mulches need to be dried, otherwise they will form a mat that will stop water from penetrating and may also cause the soil to become anaerobic.

They will use up nitrogen as they break down.

Only use mulch from untreated materials

A layer of at least 50mm should be applied but we usually put it on at around 100mm in order to suppress weeds and last longer.

The soil should be watered well before applying the mulch.

Mushroom compost

What is it?

-spent mushroom compost is the left over compost medium in which mushrooms are grown

Properties

-although it doesn’t have much nutrient value left, it is valuable as bulk organic matter as it is made up of hay, straw, corn cobs, poultry and horse manure, cocoa shells, peat moss and other organic material. This makes it a good soil conditioner.

Availability

-most gardening stores will stock it

Comments

After the mushrooms have been harvested, the compost is usually pasteurized (with steam) to kill insects, pathogens and any remaining mushroom particles. For me, this means there is no “soil life” so I wouldn’t use it as a substitute for good organic compost but instead as another supplement.

Some sources say it is a great fertilizer and soil conditioner; others say it is ‘spent’ and doesn’t have much nutrient value left. It is valuable as bulk organic matter as it is made up of hay, straw, corn cobs, poultry and horse manure, cocoa shells, peat moss and other organic material.

My other concern is about what is added by the mushroom farmer in the way of chemicals to combat the pest and fungal problems they encounter. Perhaps putting it in the compost and have it go through the process again will eliminate those concerns.

 

Neem cake

What is it?

  • this is a solid form of neem, left over after the oil has been pressed from the seeds of the neem tree.

Properties

  • has pest-controlling properties
  • excellent fertilizer and soil conditioner
  • anti-fungal properties
  • rich in nitrogen, phosphorus, potassium, carbon, sulphur, magnesium and calcium
  • accelerates root development and overall plant growth. 

Comments:

We will add it to the soil along with other fertilizers when the beds are being prepped.

Peat moss

What is it?

  • partially decomposed sphagnum moss

What does it do?

  • retains moisture
  • aerates soil
  • lowers the pH of the soil as it is very acidic

Comments

It is often used in potting and propagating mixes

It is not desirable to use in compost as it takes too long to break down

Peat moss is losing favour in the organics industry as it not a renewable resource (peat wetlands are being depleted). A comparable alternative is “coir peat” (see information above).

Perlite

What is it?

  • naturally occurring mineral produced by the rapid heating of volcanic glass

What does it do?

  • holds moisture but allows the soil to drain well
  • helps with aeration
  • prevents the soil from compacting
  • slightly alkaline (pH 7-7.5)
  • doesn’t break down so its effects on the soil are permanent

Availability

Sold as pure white granules

Comments

Perlite granules have small cavities on their surface which allow them to hold moisture.

It is mainly used in seed and propagation mixes

Rock minerals

What is it?

  • ground rock

Properties

  • excellent source of a wide range of minerals and includes rock phosphate, dolomite, limestone and rock dusts from silicate rocks (e.g. basalt and bentonite).

There are a variety of types of crushed rock available 

Rock phosphate

  •  slow working
  •  won’t matter if you over-apply
  •  can take over 12 months to become available to plants but if put into compost it will be available when the compost is mature.

Dolomite - consists of calcium carbonate and magnesium carbonate

Crushed limestone - pure calcium carbonate

Natural gypsum

  •  breaks up sticky clay soils
  •  form of calcium

Green sand - crushed sandy rock or sediment

  •  contains a large amount of glauconite (formed in marine deposits), potassium, phosphorous, iron, magnesium and other elements
  •  slow release
  •  has the ability to absorb large amounts of water.

Crushed basalt - originates from volcanic activity

  • excellent source of minerals including silica

Granite dust - slow release potash i.e. potassium

Bentonite clay - an impure clay formed by the weathering of volcanic ash by water

  • different types of bentonite clays are categorised by the main element they contain e.g. sodium bentonite, potassium bentonite, calcium bentonite.
  • has the ability to absorb a great deal of water and is used as a ‘wetting agent’
  • calcium bentonite is the bentonite clay used in gardens, as it is more stable and holds and releases water more effectively than the other clays.
  • its water- and nutrient-holding capacity make it a particularly good additive for sandy soils

Palagonite - derived from basalt rock which has been vitrified (turned into glass) as a result of volcanic activity.

  • contains macro-and micro-nutrients including silica.

Availability

From garden supply stores.

Comments

Adding rock dust to depleted areas will remineralize them.

May be added directly to the soil or to the compost heap.

If growing a green manure crop it can be added to the crop and incorporated into the soil.

Moist conditions, high temperatures and high biological activity will accelerate the breakdown of the minerals in the rock.

Potash

What is it?

Potash is a salt rich in potassium formed from dried deposits of minerals originating in ancient seas, ground into a powder. It can also be produced from salt saturated water (brine) of salt lakes where the water is evaporated leaving the crystallised salt.

Properties

  • naturally occurring form of potassium

Availability

Sulfate of Potash is preferable as it doesn’t contain chloride and does contain sulphur which is an important nutrient for plants. It is available in granule, liquid or powder form.

Comments

Potash originally came from the practice of soaking wood ash in water then allowing the water to evaporate in metal pots. The residue remaining in the pots was called pot-ash.  It was the main source of potassium prior to potash being mined. Now the name refers to any compound or mineral bearing potassium.

Although it contains sulphur, it is not in a form that will have any significant effect on the  pH of the soil

Sawdust

What is it?

  • fine particles of wood; a by-product from timber industry

What does it do?

  • good source of carbon for the compost

Comments

I don't  recommended  it as a garden mulch as it decomposes rapidly, using up nitrogen, thus depriving the plants. It also forms a crust which will prevent water from getting through to the soil.

Only use sawdust from untreated timbers.

Sea minerals

What is it?

  • concentrated minerals and trace elements obtained from sea water, with the salt removed.

What does it do?

  • whilst they doesn’t have much NPK (nitrogen, phosphorus, potassium), they have plant growth hormones
  • boost plant health, helping the plant to cope with stress from the weather and disease

Availability

In liquid form from garden supply stores

Comments

There are more nutrients immediately available in sea minerals than with seaweed or fish emulsion.

Seaweed

What is it?

  • primitive ocean plants

What does it do?

  • although it is not high in nitrogen or phosphorus, it has a reasonable amount of potassium
  • it has an amazing amount of trace elements, growth hormones, fungal food and disease-fighting properties. It has a broad and balanced range of nutrients
  • stimulates microbial activity
  • will help in correcting deficiencies in micronutrients
  • helps to control downy mildew; use in conjunction with fish emulsion to give plants an added boost.

Availability

  • as ground seaweed, seaweed meal and pure liquid seaweed. 

Comments

It is good to combine it with a high nitrogen fertiliser, such as fish emulsion, to create a complete fertiliser

Liquid seaweed is good to use because it is difficult to overdose the plants

Fresh seaweed is excellent in compost as it breaks down quickly, but all traces of salt must be washed off before it can be added.

Agar is a seaweed extract which can be mixed with water and used as a wetting agent; especially good for sandy soils.

TIP- We would give our seedlings a dip in seaweed solution just prior to planting out as it seemed to reduce transplant stress. Immerse the roots in the solution, either by letting the seedling tray sit in the solution or giving them a quick dunk as planting (trying not to lose too much soil from around the roots).

Shell grit

What is it?

  • crushed oyster shells containing 95% calcium carbonate
  • can use ground up eggshells as an alternative

What does it do?

  • will slowly release calcium over an extended period.

Vermiculite

What is it?

  • naturally occurring type of clay that has been heated to make it flaky

Properties

  • sterile, odourless and fireproof
  • aerates soil
  • improves drainage
  • conditions soil
  • retains a high volume of water
  • has a high cation exchange capacity (ability to hold nutrients)
  • will increase the soil pH a little
  • doesn’t break down

Availability:

Sold as shiny brown flakes

Comments

Usually added to potting and seedling mixes as it keeps the soil moist without becoming soggy.

Wood ash

What is it?

  • ash from a fireplace, stove or bonfire

What does it do?

  • good source of potassium, phosphorus, magnesium and trace elements with calcium being the most abundant nutrient

  • will increase the pH of the soil as the calcium carbonates and oxides act as liming agents making it quite alkaline

Availability

Usually household

Comments

The level of potassium and calcium carbonate will vary with the type of wood burned.

Briquette or coal ash is not suitable as these manufactured products often have chemicals added to make them burn faster.

The type of ash produced will be determined by the wood burned; generally hardwoods retain more nutrients than softwoods

Only add small amounts to compost or when sprinkled around the base of plants as its salt content may affect the plants  

Ash resulting from burning banana skins, citrus peels or cucumbers is high in potassium.

Zeolite

What is it?

  • natural mineral formed millions of years ago from the glass component of volcanic ash

Properties

  • has a ‘sponge-like’ molecular structure with a lot of surface area, giving it a high cation exchange capacity (it is negatively charged whereas the elements are positively charged, so it can hold them in the soil).
  • improves drainage

Comments

It has the ability to attract and absorb water and nutrients, also acting as a reservoir by holding these and releasing them slowly as the plants require them. Consequently, nutrients are less likely to be leached out of the soil and fertilising can be kept to a minimum.

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