The soil is like the foundations of any garden; if you get the soil right, you will have a beautiful, successful garden. If not, the garden will never look its best, the plants will be sickly looking or die, and will be more prone to pests and diseases.  Unfortunately, many people neglect the soil because they do not know what it requires and this includes many landscapers as well. So many people do not even think about the soil, or what it takes to keep it healthy. For instance;

• One of the worst things people can do to their soil, is use chemical or artificial fertilisers. These are quite destructive to the soil structure and the microbiological organisms within the soil.
• Another big mistake people make is using soil sterilising poisons to control weeds, which is also incredibly disastrous.
• The use of weed mats to control weeds is a major health problem for the soil because it restricts micro and macro-biological activity, water penetration, and gas exchange between the soil and the atmosphere.
• Using cut-and-fill techniques when building or undertaking construction work, as discussed further down this page.
• Different soil types require different watering cycles, and have different drainage requirements.
• All soils require organic matter to be healthy, in the form of compost, mulch, etc, and this usually needs to be added by humans initially to kick start the composting cycle in a new garden. Not using mulches or compost will cause problems in the garden sooner or later.
• Large areas of paving or concrete restrict the gas exchange between the soil and the atmosphere, restrict rain penetration into the soil, and doesn't provide any organic matter to the soil beneath it. This can be a major factor to soils becoming infertile, and sickness in plants surrounded by such hard-scape surfaces.

There are, of course, many people who believe that what we have done to our soils in the past has had no affect over all to our soils now. They base this on the fact that plants can still grow in our soils, so therefore soils must be self repairing and we can do whatever we want to them with no consequences. Well, how wrong these people are! For those of you who have heard of Colloidal Minerals, you may know that these are the trace elements and minerals that were present in the soil at the time of the Dinosaurs. There were around 90 or so of these trace elements and minerals present in the soils back then, all of which play a vital role in the health of plants, animals AND humans. Because of our land clearing habits, poor farming techniques, poor recycling and composting habits, and overuse of chemical fertilisers, etc, only 11% of these naturally occurring trace elements and minerals are present in today's soils!!! That is a huge amount of essential minerals and elements that we have removed from the Earth through soil destruction! And, as humans, we consume plants that grow in soil deficient in these minerals that our bodies need, eat animals that eat the deficient plants, and then wonder why our bodies these days are not as healthy as they should be! We take multivitamins in an attempt to replace these lost minerals, but it's just not the same. Caring for our soil is probably the most important thing any gardener can do to help the health of our planet.

Soil Types

There are three basic soil types;

Sand

Sand is made up of large granules and contains mainly quartz material with very few micronutrients. It is a free draining medium with little or no organic matter to hold any applied nutrients

Loam

Loam usually contains some sand or silt (a mixture of fine sand and clay), together with clay and decomposed organic matter. The texture is crumbly, and the loam contains humus which imparts a dark colour. Loam soils are the best for growing plants because they offer good drainage, can retain nutrients and contain naturally-occurring minerals.

Clay

Clay soils are mainly composed of very fine particles, like talcum dust - closely packed, solid and heavy. Clay soils contain lots of minerals, but are usually so dense that they have poor aeration and poor drainage, and tend to become over-wet so that they will not support plant growth.

Soil Profiles

Any of the above soil types may be found mixed within the soil profile of a particular area, to create different categories such as clay loam, sandy loam or sandy clay loam. Within the Australian continent, very few rich, deep soil profiles are found. Most have a very thin loamy topsoil containing some organic matter, with an underlying clay layer or subsoil, although there are many sand ridges created by ancient river systems or ancient inland seas, and a very few deep pockets of rich volcanic soils. What this means is that gardeners need to pay lots more attention to enriching the soils, to keep the topsoil fertile for future generations.

Cut-and-Fill Techniques

Below is an article taken from the book " No Garbage", written by Allen Gilbert and first published in 1992 by Lothian Publishing. Some slight editing has been made, and some personal points have been included, which are shown in italics.

The cut-and-fill mentality of landscapers, land developers and house builders in Australia has exacerbated the problems associated with clay soils in garden areas. With this operation, the site is levelled by cutting into a slope and using the material that is cut out to fill depressions or to extend the levelled site. This buries too much topsoil or mixes it with too much clay which destroys the overall soil structure. When land has been levelled using cut-and-fill techniques, most home gardeners must either try planting into solid clay, rebuild their garden soil, or buy expensive soil to make gardening possible. Not to mention the drainage problems it creates! Rain will collect in clay areas because clay soils have a very poor infiltration rate, and when cut-and-fill methods have been used to build a house, this pooling is usually right at the house, which can cause structural problems.

Mixing clay with topsoil will generally destroy the topsoil structure. The mixing of sand with clay is often mentioned in gardening books, but is not recommended here because of the huge amount of sand needed to noticeably improve the soil structure. Clay soils are composed of billions of dust-like particles, so small and numerous that they clog any soils mixed with them, preventing drainage and limiting the amount of oxygen available to plant roots. However, clay soils can be improved by mixing in huge quantities of organic matter such as compost, by adding gypsum with the organic matter, by providing drainage by means of pipes, or by using raised beds, mounds or ridges for planting. It is a fallacy to think garden soils are well drained because they are on a slope. Slopes will get rid of surface run-off water, but will not give adequate drainage within and through the soil if that soil is poorly structured. This is especially relevant to heavy clay soils.

Soil pH

The acidity or alkalinity of soil is expressed by a number known as the pH value. The pH scale ranges from 0 to 14, with the middle reading of pH 7 being neutral. Some plants prefer alkaline soils because of the minerals present in them, while others prefer acidic soils for the same reason. Some people try to artificially raise or lower the soil pH levels in an attempt to create conditions for their favourite plants. This is done by adding lime to raise the pH level, or sulphate of ammonia, peat moss, or powdered sulphur to lower it. Although this works to a degree, it is much better to choose plants that will thrive in your soil pH as it is. An incorrect soil pH will kill the micro organisms present in the soil, some of which are actively involved in supplying nourishment to the plants or have some other symbiotic role. Research has shown that specific symbiotic organisms exist in the soil alongside plant species, breaking down materials into a form that can be absorbed by the plant roots. An organic, living soil will supply a larger range of nutrients than many management techniques, over the whole pH range. So basically, don't mess with nature. Try to work with her. She has been doing this for millions of years, so I think she knows what she is doing. If you have a soil pH level that does not meet the specifications of your favourite plant, find a substitute, or grow that plant in a large pot. Trying to alter the pH of the soil artificially will be an ongoing task, and will probably be a waste of time in the end.

Soil Salinity

Salt levels in Australian soils are becoming more and more of a problem every year, and this is mainly due to the destruction of our natural bush lands and forests. Trees used to keep the salt levels in the soils low by taking ground water and rainfall through their roots. Now that they are gone, we are suffering the consequences. If the salt level in the soil becomes too high, plant growth is retarded except for those species, like Saltbush, which have adapted to such conditions. Rising ground water levels pushes the salt to the surface, and in some cases, can render the soil infertile. Our Murray River system is disastrously salty, and so for people living on the river, or who use the unfiltered river water for irrigation, soil salinity is even more of a problem. Not only does the soil already have an increase in salt level, but they water their plants with highly salty water too! I have seen trees suffering salt burn on their leaves at Langhorne Creek, but the owners didn't seem concerned at all. Their solution was to add more water in an effort to dilute the salt! So not only did water restrictions mean nothing, rising salt levels was no concern either! What disastrous mess are we going to be leaving our future generations?

Soil Movement

Most people understand that soil moves over time. Most people are aware that soil movement can crack building foundations, and lots of home owners in the Adelaide region know this first hand. Housing foundations are quite often at least 300mm thick, sometimes more, and it seems acceptable to understand that soil movement will crack and damage foundations this thick. Why then do people have an issue with soil movement moving pavers that sit on a base that is maybe 100mm thick? And a base of dolomite that is, not concrete. People accept that concrete will crack with soil movement, but believe that pavers should never move, and if they do, the installer must be shonky, has ripped them off, and he is bad at his job. These people have an extremely strange way of thinking. The truth is that soil movement occurs everywhere, all of the time, and cannot be stopped. It is a natural phenomenon which humans cannot, and are not supposed to, stop. And if a thick concrete slab is not safe, nothing really is. Because of the way some developers work, using fill to build land up, cut and fill techniques, reclaiming swamp areas by filling them in with different soils, etc, soil movement will be more prominent in these areas, and relatively new homes will show evidence of soil disturbance, as will paving, etc. Before you build your next home, be sure to check with the developers, local councils, local residents, etc, what the area was like before the land was prepared for building sites. When will developers get it into their thick heads to work with the land, not on top of it? The unfortunate thing is that because the landscaper is generally the last to work on the property, we are the ones who cop the full brunt of disgruntled home owners who believe it is us who has made their soil shift, and it is us who are left to defend our reputation and our livelihood against false accusations.

Soil Wetting Agents
 

These agents, when applied to the soil are long lasting and help the water to penetrate deeply and evenly increasing the moisture retention in the root zone, saving water by reducing the run off; at least - that's the theory.   The use of soil wetting agents is not recommended on the Fleurieu Peninsula because, they can be destructive if applied incorrectly. Natural, native bushlands and forests don't need them, so why does a private garden?? You can save water by watering wisely, using dripper irrigation instead of sprinklers, etc. Don't add anything artificial to the soil if you don't have to.