Creating good soils by Community Gardens Australia

Creating good soils

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the most important part of organic gardening THINKING ABOUT SOILS

THE VALUES OF GOOD SOIL

A REGENERATIVE RESOURCE

Fertile, nutritious soils are the basis of prolific, productive organic gardens. Good gardening starts with good soils.

In this publication we propose that gardeners improve their garden soils by making their own fertiliser in the form of compost. Doing this is to turn what is a waste disposal problem into a solution.

Soil is like any other resource. We deplete it as we make use of it, so we have to replace the nutrients taken up by our plants and removed from the soil habitat when we harvest.

Soils are a habitat. They consist of: ■ a non-living part made up of the minerals such as sand and clay ■ air ■ the living part of the soil made up of insects and bacteria, virus and fungi. A fertile soil is a matrix of life. To garden and grow food successfully we create a habitat in which soil life, including that which we plant, can flourish. Like people, plants need a balanced diet of nutrients. In the organic garden these come from the soil. We create the soil—this habitat for soil life—by understanding how soils work and by working with nature. Knowledge of soils leads to cooperation with nature and, as our crops thrive, to good, tasty food.

Managing soil for fertility: ■ is the basis for producing some of the food we eat ■ offers us an understanding of how we can apply science in the home or community garden—in other words, soil management contributes to learning ■ encourages mutual assistance and conviviality when done with others ■ benefits wildlife such as insects, small reptiles and birds ■ make our towns an cities productive places ■ sequesters carbon.

Fortunately, we can regenerate soil by turning our garden and kitchen wastes—anything that was or is living—into compost and adding that to our garden. It helps to think of our garden soil as a living thing requiring its own inputs and management.

HOW SOILS ARE FORMED Soils are formed over time by: ■ physical weathering — the disintegration of rock, known as parent material, into small particles and, finally, into soil minerals through the action of climatic influences such as temperature, rainfall, freeze and thaw cycles ■ chemical weathering — the chemical alteration of particles through the action of organic acids from the breakdown of plant material, minerals and other chemicals present in the soil.

Improving soil in a raised garden bed using compost and straw.

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SOIL COMPONENTS

WHAT MAKES UP SOILS?

The soil is made up of a range of materials and provides habitat to large numbers of lifeforms.

Soil types Soils span a range of types between sand and clay. SAND: ■

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a granular material composed of finely divided rock and mineral particles weathered from parent rock particles range in diameter from 0.0625 to 2 millimeters is usually laid as depositional deposits transported by water or wind drains freely—it does not retain much moisture around individual grains holds few plant nutrients around the particles and makes a poor growing medium for fruit, herbs and vegetables is added for drainage to potting mixes and growing media for container gardens.

Minerals

Formed from parent material.

Organic matter

Formed by decaying plant and animal material infiltrating the soil from the soil surface.

Living organisms

Lifeforms for which the soil is their habitat: bacteria, fungi, burrowing animals, virus.

Air

Held in pore spaces between soil particles.

Water

Held in pore spaces between soil particles.

CLAY: ■

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consists of fine-grained minerals smaller than those of sand and silt is elastic or exhibits ‘plasticity’ depending on water content may be laid as depositional deposits transported by water retains moisture and plant nutrients around the particles; these form a reservoir of nutrients that are accessible to plant roots; clay is a more nutritious soil type than sand for the cultivation of fruit, herbs and vegetables unless it is a very heavy clay that resists penetration by plant roots.

SILT: ■

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LOAM:

Loams are mixtures of sand and clay that are classified according to the portion of each of these in the soil ■

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Soil with a fine texture and a component of clay can be moulded into a ribbon.

ORGANIC MATTER Organic matter is a component of soils that includes anything alive or once alive. It is also added to soils to improve fertility in the form of compost, vermicompost (compost produced in a wormery), liquid compost and by the decomposition of mulch.

SOIL PROFILE Seen in section, the soil can be divided into three layers—A, B and C horizon.

A horizon: topsoil, humus from broken down organic matter; insects and lifeforms. B horizon: material consolidated from A horizon; less life. C horizon: soil degrading from parent material (such as rock); less soil life, organic matter. Graphic: https://en.wikipedia.org/wiki/Soil_horizon

fine-grained particles that do not include clay minerals are between sand and clay in particle size although there may be some overlap in both particle size and other physical properties laid as depositional deposits carried by water or wind contain plant nutrients.

composed of sand, silt, and clay particles (about 40%-40%-20% concentration respectively) considered ideal for gardening and agricultural uses because they retain nutrients, moisture and humus (a fine material formed by the decomposition of vegetation) but drain well and are easier than clay to work with.

Hydrophobic soils These are soils that repel water due a waxy coating. They are common in sandy soils. Improve the soils’ water holding capacity by adding: ■ an organic mulch ■ a fine clay such as bentonite (found in products like RichGro’s Ezi Wet) ■ an organic wetting agent (such as Munns Wetta-Lawn & Garden) ■ agar, a powdered kelp ■ more about wetting agents— https://jerry-coleby-williams.net/20 07/02/27/wetting-agents-are-you-b uying-trouble/ ■

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SOIL ACIDITY AND ALKALINITY Soils vary in their acidity between acid and alkaline. The acidity or alkalinity of soils is measured as their pH on a scale from 0 to 14. A reading of 7 is regarded as neutral. The scale is logarithmic — each number is ten times more or less acidic or alkaline than that either side of it. Soils that are too acid or alkaline may not take up the nutrients required by the particular plant, inhibiting its growth.

For the science-minded pH is a measure of dissolved hydrogen ions. An ion is an atom or molecule that has lost or gained one or more valence electrons (valence is a measure of the number of chemical bonds formed by atoms), giving it a positive or negative electrical charge. A positively-charged ion, which has fewer electrons than protons, is known as a cation.

Plant preferences

Testing the soil for pH

Different plants prefer different pH conditions: ■ Australian native plants in the southern and eastern part of Australia prefer a slightly acid soil ■ vegetables prefer a pH around 6 to 7.5.

For home and community gardeners, the chemical test to identify the pH of garden soils is the simplest and cheapest. This is carried out through the use of a soil pH testing kit that consists of: ■ a bottle of liquid chemical reagent ■ a bottle of powder to bring out the colour of the chemical reaction ■ a colour chart with swatches corresponding in colour to pH 0-14 ■ a white plastic panel for mixing the reagent and soil on ■ a plastic stick to mix the reagent into the soil ■ instructions.

ACIDITY TOLERANCE OF VEGETABLES Tolerance

Crop

Very tolerant—down to pH5

potato, rhubarb, shallot, watermelon

Moderately tolerant—down to pH5.5

beans, brussels sprouts, capsicum, carrot, cucumber, eggplant, garlic, horseradish, parsley, pea, pumpkin, radish, tomato, turnip

Slightly tolerant— down to pH6

asparagus, beet, broccoli, cabbage, spinach, rockmelon, cauliflower, leek, celery, lettuce, onion, silverbeet

Plastic is preferred for the mixing stick to combine reagent and soil sample as wood contains acids that could contaminate the reaction and produce a false reading.

SOIL COMPONENTS AND THEIR PROPERTIES FOR GARDENING Soil component

Sand

Clay

Air

Well aerated

Potential for poor aeration

Drainage

Free draining.

Potential for poor drainage.

Low water holding capacity.

Higher water holding capacity.

Low fertility.

Fertile.

Water leaches nutrients through soil.

Nutrients and moisture are held within the soil structure.

Easy to work.

Can be difficult to work.

Soil particles do not hold together well.

Particles stick together.

Texture

Coarse grain—large particles.

Fine texture—small particles.

Feel

Gritty

Sticky

Add organic matter to:

Fertility Workability

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increase nutrients improve water holding capacity.

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open the soil structure improve drainage improve aeration.

ORGANIC FERTILISERS

TYPES OF ORGANIC FERTILISERS

EFFECT OF SOIL pH ON PLANT NUTRIENTS

Fertilisers are chemical compounds—organic or inorganic—applied to soils or to plants to stimulate growth.

Organic fertilisers are those made from materials that are or that were living.

Nutrients to plants become less available as acidity and alkalinity increase.

Slow release fertilisers provide a sustained release of nutrients over time.

An excessively acid or alkaline soil is likely to produce weak plants.

Depending on type, fertilisers may be applied: ■ to soils from where they are taken up by plant roots ■ to foliage—foliar feeding, by spraying liquid fertiliser onto the leaves through which it enters the plant cells. Fertilisation provides to plants: ■ the three major plant nutrients—nitrogen, phosphorus, potassium (N-P-K) ■ secondary nutrients—magnesium, calcium, sulphur ■ trace elements or micronutrients such as—boron, manganese, iron, zinc, copper, molybdenum.

Fast release fertilisers are quickly taken up by plants and have less benefit to the soil. Fast release fertilisers in liquid form hold nutrients in solution.

Wormwater, the liquid drained from the lower collection trays of commercially-made wormfarms is a fast release liquid fertiliser. It usually requires dilution before application to plants to a weak tea colour.

Causes of acidity: ■

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loss of nutrients due to leaching or plant uptake use of acid-forming fertilisers breakdown of non-organic matter releasing hydrogen ions (electrically charged particles) acidification due to soil pollution.

Causes of alkalinity: ■ ■

excessive addition of lime to soil irrigation with hard water.

ORGANIC FERTILISERS—BENEFITS TO SOILS Fertiliser

Benefit

Slow release: ■ ■ ■ ■

compost vermicompost (worm compost) animal manures decomposing plant material

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improves soil structure improves water holding capacity assists in the biological control of soil-borne plant disease.

Fast release: ■ ■ ■ ■

liquid seaweed solution fish emulsion wormwater (liquid fertiliser from wormfarm) liquid compost—made from plant material decomposed in water.

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rapid uptake by plant feeder roots (finer roots growing from the main roots)

The white material growing in this compost is fungi, one of the decomposer organisms that appear in compost systems.

Far left: Gardeners add carbon-rich paper to enclosed wormfarm bays designed to produce large volumes of composted material. Left: Compost heap covered with paper or hessian bags to retain moisture.

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MAKE YOUR OWN ORGANIC FERTILISER Making our own fertiliser is easy. It’s cheap too—we can make it from our food scraps, garden wastes, lawn clippings and plant prunings. Composting is a process of combining materials that are or were alive and allowing them to decompose into a form useable as fertiliser. The use of organic fertiliser declined with the introduction of synthetic fertiliser in the 1930s, a trend which accelerated in the 1950s. Organic fertiliser, however, has been the traditional method of soil improvement for thousands of years and now, through organic gardening, is regaining its popularity. Compost, blood and bone and animal manures such as dynamic lifter—pelletised chicken waste—are commonly-used organic fertilisers.

Compost as a source of organic fertiliser The composting of organic wastes to make fertiliser is a means of increasing the fertility of our soils and replacing those plant nutrients in our garden soils that are removed when we harvest our vegetables and herbs. Nutrients become bound up in plant cells and, when we harvest or clear crop residue (the organic matter left after removing the edible part of the plant) from the garden, we also remove those nutrients that have been extracted by the plants from the soil. With around half of our household waste consisting of organic matter, its conversion into fertiliser turns what is usually thought of as a problem to dispose of into its own solution—a useful product for our gardens.

Open compost bays and a variety of compost bins turn garden waste into fertiliser at Randwick Community Organic Garden.

With more people living in town houses and apartments or who have only small gardens, worm farms and the Bokashi composting system are an alternative to the compost bin. Some apartment residents have started communal compost systems. COMPOSTING—THE BENEFITS

The benefits of composting include: ■ supplying nutrients to your plants ■ increasing the nutrient and moisture holding capacity of your garden soil ■ conserving water—more water is held in the soil ■ improving drainage in clay soils. TWO WAYS OF COMPOSTING

We can think of compost as the aerobically or anaerobically decomposed remnants of organic matter. ■ aerobic compost is that produced in the presence of air; it is the most common method of compost production ■ anaerobic compost is that produced without air; an example is liquid compost that is produced by decomposing organic matter into liquid; anaerobic processes are potentially odourous—that is, they can smell bad and so require careful thought as to where they are placed so they don’t stink out the neighbours.

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COMPOST CONTAINERS

First, you need something to make the compost in. Usually, you have the alternative of: ■ home made compost bays; the three bay model is popular because it allows for a bay currently being filled with organic waste, a filled bay in which waste is in processing and a curing bay with close-to-finished or finished compost ready for the garden; this is a scaleable model ■ commercially available, plastic compost bins of various types ■ covered heaps ■ commercially available compost tumblers—rapid composters. With the exception of the compost tumbler, the contents of the other types can be: ■ turned weekly or so to ensure the rapid production of compost—the ‘hot composting’ method; regular turning discourages rodents ■ left unturned—the ‘cold composting’ method which works more like a worm farm; compost for the garden is extracted from the bottom of the bin where material that has been in processing the longest.

COMPOST INGREDIENTS

An easy way to think about what to put into compost is to remember the ADAM principle, an idea developed for the NSW Earthworks community waste education course in the 1990s: ■ A—aliveness; anything that is or was alive ■ D—diversity; a diverse range of materials ■ A—aeration: air is needed for the decomposition process; aeration is achieved with regular turning of the compost ■ M—moisture; another necessity for the composting process; this can be added, if needed, when turning the compost.

CARBON AND NITROGEN MATERIALS

About 25-30 parts of carbon to 1 part of nitrogen-rich material provides the right balance for composting. Adding a diversity of material helps us achieve this ratio. Materials rich in carbon: sawdust—450 carbon to 1 nitrogen ■ paper—170:1 ■ leaves—60:1. ■

Materials rich in nitrogen: ■ lawn clippings—20:1 ■ food wastes—15:1 ■ cow manure—12:1. Source: Composting (Discover Soils booklet no. 5); CSIRO.

GREEN AND BROWN

What goes into the compost bin? Anything that is or was alive. For beginner composters, it is best to avoid meat, fats and dairy as these can attract rodents if not properly composted. Avoid weeds in seed as they may still propagate. What our compost does need is a mix of nitrogen-rich materials (nitrogen is a plant nutrient) and carbon-rich. We can think of these as green and brown. So, following the ‘diversity’ principle of making compost, we add a range of materials that are predominately green (nitrogen) and brown (carbon).

Layering ensures that a good mix of carbon-rich and nitrogen-rich materials go into making the compost. They become mixed when the compost is turned.

The Bokashi composting system uses a bacterial mix added to food waste in a sealed plastic container to ferment it to a condition suitable for burying in the soil. The waste reduces in volume as the liquid in it drains into a lower tray from where it is accessed via a tap. It can be used as a liquid fertiliser on pot plants and gardens. Bokashi is designed for making in the kitchen.

Adding carbon-rich materials—dry leaves—to a domestic compost bin.

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MAKING COMPOST To make a fast, hot compost with the right mix of diverse ingredients, whether in a bin, open bay or heap, we: 1 Place compost bin or heap in a sunny position; the bin or heap should be at least 1 metre x 1 metre x 1 metre in volume (one cubic metre) to achieve a high temperature in the core 2 Place a layer of a layer of brown (carbon-rich) material in the bottom of the bin; this helps with drainage 3 Place a layer of green (nitrogen-rich) material over the brown, about ten centimetres thick 4 Alternate brown and green layers until the bin or heap is full 5 Add water until compost is thoroughly wet 6 Cover with a porous material such as hessian 7 Turn weekly 8 Apply to garden or pots when ready. For those making a slow, cool compost, it is simply a matter of ensuring that you have a diverse mix of carbon and nitrogen materials as you progressively add them.

Turn for a hot compost

Liquid compost

For a fast, hot compost we turn weekly or at least fortnightly.

Liquid compost is made by soaking organic matter in water.

If you have multiple compost bays, use a garden fork to move materials from one bay into the next, then back again at the next turning.

A covered container with a well-fitting lid is needed. The process is anaerobic and the odour is strong, so it needs to be contained. Rubbish bins and plastic olive barrels have been used successfully.

If you have a compost bin: 9 Take hold of it and pull it off the composting materials and place adjacent 10 Fork the materials into the empty bin 11 Carry out a squeeze test to assess moisture and add water if needed.

Test for moisture We use the squeeze test to assess the moisture content of our compost: ■ wearing gardening gloves, grab a handful of the compost from inside the heap ■ squeeze tightly—if water comes out in a steady stream, the compost is too moist and risks going anaerobic; leave uncovered until it dries out a little; if no water comes out the compost is too dry; add water; if water comes out in drips the moisture level is just right.

Place well away from the house—and the neighbours. Make liquid compost: 12 Fill container with water 13 Place organic materials in a hessian or similarly porous bag 14 Suspend the bag so that it is submerged 15 Leave until the organic materials leach into solution in the water, usually a few weeks. The solid material left after making liquid compost can be added to your compost bin. Liquid composting is a good way to deal with weeds in seed. Use as foliar spray or pour onto soil or container gardens as a fertiliser.

If you add mainly food scraps, tear up newspaper and add it to the bin to ensure that you are adding enough carbon materials.

COMPOST—ESSENTIAL INGREDIENTS ALIVENESS: Microorganisms

Microorganisms activate the composting process.

and other living things

Lifeforms for which the soil is habitat—burrowing animals, bacteria, fungi, virus.

DIVERSITY: Organic matter

Around 25-30 parts of carbon materials to 1 part nitrogen materials.

AERATION: Air

Required by microorganisms and other soil life.

MOISTURE: Water

Required by microorganisms and other soil life.

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Section through a slow composting process in a domestic compost bin. In the slow composting method, the contents of the bin are not turned. Domestic compost bins can also be used for rapid, hot composting by removing the bin and turning the compost back into it, adding water if necessary.

COMPOST MATERIALS AND PROBLEMS Material

Considerations

Meat, fish

Attracts vermin unless well covered; not for beginner composters.

Fats, oil, salt, antibiotic, pesticide, herbicide

Can kill organisms and slow the composting process.

Fruit infested with fruit fly

Composting might not kill fruit fly larvae; place infected fruit in a plastic bag in the sun for a week, then add to compost.

Dog and cat manures

May contain harmful bacteria and worms. Use a separate compost system for these manures and don’t spread the finished compost on your vegetable beds.

Large prunings, branches

How to test soils for pH

A commonly available chemical pH test kit for assessing soil acidity/alkalinity.

Too large for rapid decomposition.

Compost problems & solutions Foul smell

The compost is too moist and has become anaerobic (breakdown without air); add dry materials such as dry leaves and turn; cover when raining.

Materials slow to degrade

Insufficient: ■ nutrients—add nitrogen-rich materials such as lawn clippings, animal manures (eg. chicken, cow), blood and bone fertiliser ■ air—turn the compost ■ water—add water ■ too cold in winter—cover the compost with a porous material such as hessian.

Maggots

Remove the attractant (such as meat); cover maggots with lime; add lime to the top of the compost and turn the next day.

Rodents

Turn compost weekly to disrupt the breeding environment; open compost bays are more susceptible to rodent infestation.

Types of composters

1. Take a level teaspoon of soil from immediately below the humus layer, moisten the soil sample with several drops of indicator fluid.

2. Mix indicator fluid into the soil sample.

3. Dust the paste with the white powder and wait approximately a minute for the powder to absorb the colour of the chemical reaction. A foam insulated ‘Little Pig’ rotating composter produces compost rapidly.

Compost heap or windrow (a long heap). Cover with hessian.

Compost bays—closed and open.

Domestic composter

4. Read the pH value of the soil nearest to the colour of the sample by referring to the colour swatch card. This provides your pH reading.

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FERTILISER FROM WORMS A wormfarm produces a fine, rich and nutritious solid fertiliser as well as a liquid fertiliser that is diluted for use on plants. The wormfarm is a habitat that contains all that the worm colony needs for its subsistence—the material in which they live, food, moisture, protection. The commercially available plastic habitats consist of two deep trays with perforated bases that contain the material the worms burrow into, a base tray that collects the liquid compost that is fitted with a tap to drain the liquid compost, and a lid. The habitat will be home to different varieties of compost worms, not the earthworms found in the garden.

Make your own A wormfarm can be made from a box of around 30cm deep, 50cm or more wide and 50cm or more long. Holes are made in the base for drainage and to allow in air. A tray goes underneath to collect the nutrient-laden liquid so that it can be used as a liquid fertiliser. The top of the wormfarm is covered with hessian or a similar porous material that will slow the evaporation of water. It’s a good idea to place something over the top as a lid, especially if your wormfarm is to be located where rain could saturate it.

Setting up your worm habitat Place your worm habitat in a cool, shaded place out of direct sunlight. Into one of the trays place bedding material 10cm to 15cm deep—finished compost, coconut fibre (you can buy this as compressed, dried bricks), leaves or shredded paper. 1 Add your worms—you can buy worms in parcels of around 1000 from nurseries and hardware stores. Distribute the worms over the bedding into which they will burrow.

Section through a commercially available worm habitat. As kitchen wastes are added to the top tray the worms move into it. The worm castings in the lower tray are ready to use. Water added to the habitat leaches through the trays, picking up nutrients and accumulates in the lower tray where it can be tapped for use as liquid fertiliser.

2 Place newspaper over the top of the bedding material, place the lid and allow the worms a week to settle into their new home. 3 After the first week start adding your kitchen wastes—avoid onion and garlic, citrus and chilli, meat and milk, Add food wastes every couple days by lifting the newspaper and burying a handful. After a week or two you can lift the newspaper and place the food scraps on top of the bedding material. Feed the worms only when they have eaten most of the scraps already placed there. 4 When the tray has been filled to the marker lines visible on the inside, place the second tray on top and place some food scraps into it. The worms will move from the lower tray through the holes in the base of the upper tray.

Compost worms, not earthworms, do the work of breaking down waste into fertiliser in the worm habitat.

Below: Newspaper has been laid on top of the bedding material to reduce evaporative moisture loss.

To empty a tray, place a handful of food scraps in a corner, wait a few days until the worms move to its location then remove the vermicompost they have vacated. Liquid fertiliser can be harvested via the tap in the base tray of commercial model worm habitats. Dilute it with water to the colour of weak tea and sprinkle on your plants. Worm juice ready to use.

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IMPROVING SOILS WITH MULCH AND GREEN MANURES If we think of our garden as a cultivated ecology, then covering the soil surface with mulch models the leaf litter layer we find in the forest. Here, in a narrow zone full of soil life, leaves, twigs and animals decompose to become organic matter that infiltrates the soil profile where it is absorbed by plant roots to be remade into plant cells. It’s nature’s recycling system and we can do no better than introduce it into our home and community gardens. We do this in our gardens by substituting the leaf litter of the forest with hay or straw. As well as leaf litter if you have access to it, sugar cane mulch is a commonly available straw. Even better are pea straw and lucerne hay because they come from legumes—plants that incorporate the nutrient, nitrogen. As they decompose on our garden the nitrogen becomes available to our crops.

Living mulch

Green manures

A living mulch is a low-growing groundcover into which fruit and nut trees and shrubs are planted. It is usually planted in the orchard or, sometimes, into the beds of perennial plants (those lasting more than two years), depending on the perennials planted.

Green manures are combinations of annual plants (which go through their lifecycle, from seed to seed, within a year) that are grown then turned into the soil or slashed and left on the soil surface as a mulch before their seed ripens.

Living mulches provide the same services as straw and hay mulches. Usually, living mulches are plants of the legume family that set nitrogen in the soil where it is of benefit to our crops. Common living mulches include: ■ alfalfa, also known as lucerne ■ clover.

Benefits of mulching The benefits of mulching our gardens to around 10cm thick include: ■ reduction in the rate of evaporation of moisture from garden soils ■ breakdown into organic matter in the soil where it is accessed by our plants as nutrient ■ improving the moisture holding capacity of the soil ■ reduction of soil temperature extremes ■ reduction in the impact of heavy rain on our garden soil and the potential for erosion ■ discouraging weed growth.

Green manures can be used to fertilise nutrient-poor soils in preparation for planting vegetables and herbs. Usually, a legume combined with a grain is planted. The legume decomposes to provide nitrogen and the grain decomposes into organic matter that feeds crops and improves the moisture retention of free draining soils. Green manure mixes are climate and season dependent: ■ a warm season green manure for a temperate climate might be cow pea (a legume) and Japanese millet (a grain) ■ a cool season temperate climate mix may be woolly pod vetch (legume) and oats (grain); alternatively, broad beans (or lupin) and oats.

Lay straw mulch thickly over compost.

A green manure of woolly pod vetch and oats planted to improve the sandy soil of the forest garden area at Randwick Sustainability Hub.

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MAKE A NO-DIG GARDEN... 1. BED PREPARATION If you want to grow vegetables, choose a location for your garden bed that is protected from strong wind and that receives a minimum of four to six hours of sunlight a day. Cut long grass and clear stones and other materials like dried seeds and weeds, so they do not grow in the mulch. Cut grass can be left on the ground. Prepare the garden bed by marking it out. To deter grass from invading your garden, construct sturdy edges with material such as timber or bricks.

2. SOIL PREPARATION: the nitrogen layer — and water If you are building a garden on sandy or low-fertility soil, add a fertiliser layer about 2cm thick; compost, worm castings, manure and/or a sprinkling of dynamic lifter or blood and bone will improve soil fertility. To allow these nutrients, water and air to penetrate to the rootzone, open the soil using a garden fork. Push the fork into the soil as far as it will go, then move it back and forth to open, but not turn, the soil. Water sufficiently to moisten the soil to the root zone.

3. LAY THE WEED BARRIER: the carbon layer Cover the garden with newspaper that has been well-moistened so that it will not blow away — about 10 pages thick—or use cardboard. If you have invasive grasses like kikuyu or couch that spread by stems which grow horizontally, cover with a thicker layer of newspaper or cardboard to block light and discourage growth. Overlap by one-third their size to discourage weeds.

4. ADD A FERTILISER LAYER: a nitrogen layer Spread a fertiliser layer of compost/wormcastings/grass clippings/manure to cover the paper or cardboard. This will act as a slow release fertiliser and will become available to the plants over time.

5. LAY THE WEED-FREE MULCH: the carbon layer Lay mulch such as composted stable sweepings/hay/straw/lucerne hay on top the nitrogen layer to at least 10cm thick. A thicker layer is alright — it will soon flatten. Repeat nitrogen and carbon layers if needed.

6. PLANT SEEDLINGS AND SEEDS Germinate small seeds in pots for transplanting into the garden. Large seeds such as peas and beans can be sown directly into the bed. To plant the seedling or large seed, make small holes in the mulch to the depth of the newspaper, fill with compost and plant the seedling or seed into this. Don’t plant the seed too deep — just to twice the size of the seed. Some gardeners slit the newspaper with a trowel or knife so that the seedlings roots can penetrate the soil below.

7. WATER WELL Give the garden a thorough watering to soak the mulch.

Stay well, stay healthy... Compost and stable sweepings may contain living organisms that, on rare occasions, could cause illness. Precautions include: ■

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moistening compost/mulch to avoid micro-organisms becoming airborne wearing gloves to protect broken skin washing hands after handling materials

References ■

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wearing a dusk mask if you suffer from asthma or respiratory disorders if you handle animal manure, such as found in stable sweepings, consider vaccination against tetanus protect yourself from sunburn with suncream and hat drink plenty of water while gardening.

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Dean E, 1990; Esther Dean’s Gardening Book; Angus & Robertson, Australia Morrow R, 1993; Earth User’s Guide to Permaculture, Kangaroo Press, Australia Handreck K, 1993, Gardening Down-Under; CSIRO, Australia

FERTILISER PLANTS Comfrey

Legumes

Comfrey is a useful, perennial plant for your garden. It’s grown in your perennial garden bed, not where you grow your annuals where it will get in the way when you want to remake your annual garden.

Legumes are plants that make the important plant nutrient nitrogen available to our plants.

Comfrey is a deep rooted plant known as a ‘dynamic accumulator’ because its long roots access the nutrients lying deeper than the root systems of herbs and vegetables. It turns these nutrients into foliage which we can slash and use as a mulch or add to our compost. That’s how we get access to those deeper-lying nutrients. Comfrey, close planted in double rows, is also useful as a weed barrier around gardens where it forms a living fence. In temperate climates it can be slashed in the cooler months when plant growth is slow and allowed to grow back to full size when warm weather returns. Comfrey also flowers, making it of value in attracting pollinators and beneficial insects.

Nitrogen is produced by rhizobium bacteria living as colonies in small nodules attached to the root system of legumes. This is a mutually beneficial or symbiotic arrangement. The rhizobium bacteria convert nitrogen in the soil air into nitrogen compounds that can be absorbed through the roots of plants. In return, they extract carbohydrates from the host plants. Legumes can be planted to prepare nutrient-poor soils for gardening: ■ as a green manure of annual species turned into the soil or slashed and left on the soil surface as a mulch (the ‘slash and mulch’ or ‘chop and drop’ process ■ as a living mulch of a perennial, low-growing legume (such as alfalfa or clover) around fruit and nut trees and shrubs or in an orchard ■ as intercropping, by planting annual or perennial legume groundcovers or shrubs spaced between fruit and nut trees and shrubs, or planted within, or as an edge to vegetable gardens ■ in agriculture, as rows of legume trees or shrubs between which the main food crop is grown; this is alley cropping.

Clover is a low-growing, perennial legume suitable as a living mulch around fruit and nut trees and shrubs.

Above: a green manure of millet (to add fibrous, water-retaining organic matter to the soil) and the legume, cow pea. Below: Leguminous mulches ready for the garden are available commercially—lucerne and pea straw mulch.

Above: Comfrey Right: Pigeon pea (Cajanus cajan) is a perennial, leguminous shrub the foliage of which is slashed as a mulch in warmer climates where it will regrow rapidly. It is used as an interplant among fruit and nuts or adjacent to vegetables gardens.

Community Gardens Australia PRODUCED by… Community Gardens Australia DESIGN, TEXT & PHOTOS by… Russ Grayson

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