More Links
Queensland Soil Types
Look for regional gardening and environmental groups (who might be able to supply information on local soils) on the Regional pages.
General Information
Note that commercial products, regulations, plants and soil types vary from place to place, so some information in links may not apply where you live.
Understanding soils A number of factsheets can be downloaded from this page. Queensland Dept Environment & Resource Management
Soil health for vegetable production in Australia This soil science manual, which should be of interest to serious gardeners and students of horticulture as well as farmers, can be downloaded in PDF formfrom this page. Department of Employment, Economic Development and Innovation
What is Soil? Basic overview. Department of Primary Industries Victoria
Soils (General) State of Victoria, Department of Primary Industries, Victoria
Soil biology basics factsheets on a variety of topics available from this page. NSW department of Primary Industries
SERG Soil Ecology and Restoration Group, San Diego State University, USA
Water penetration and retention
Does gypsum improve clay soils?
There's a widespread misconception, even amongst horticulture professionals, that gypsum can improve the structure of every clay soil. Check out the following links:
pH
Soil pH Colorado State University Extension
Lawn and Tree Myths (do pines make soil acidic?) Washington State University Clark County Extension
Cation exchange capacity
Cation exchange capacity (CEC) is a property of soils and growing mixes that is rarely discussed in mainstream gardening literature. However, it plays a very important role in nutrient-retention by soils which subsequently affects fertiliser efficiency and plant growth.
Many important plant nutrients, when added as fertilsers or released from breakdown of insoluble minerals and decomposition of organic matter, exist dissolved in in soil moisture (the soil solution) as negatively-charged ions (cations). Examples are potassium, magnesium, calcium and ammonium nitrogen.
In dissolved form, there's a limit to the amount of nurients that can be stored in the soil and they are vulnerable to leaching.
Fortunately, certain types of positively-charged substances in soil have the ability to cling onto cations, while keeping them relatively available for uptake by plant roots. Cations can re-enter the soil soilution by swapping places with other cations in solution.
The "cation exchange capacity" of a given soil will depend on the amount and type of such substancess it contains. Clays generally have a high CEC (although it it varies with the type of clay). Sand has none. Humus also has a high CEC, and is one of the ways in which organic matter improves soil.
Note that sodium is also a cation. Swamping the clay particles with positve charge affects soil structure and is one of the problems associated with salinisation of soils. More about this at a later date.
The above is a very simplistic introduction to CEC for those unfamiliar with the term. If you'd like to investigate this topic further, here are a few links to get you started:
Organic Matter, Carbon
Plant nutrients
Soil factors such as acidity and cation exchange capacity will affect the behaviour of nutrients with the soil and availabitlity to plants. The nutrients themselves are covered in more detail on the Plant nutrition and nutrient deficiencies page.
Salinity
Soil testing
Other
The Myth of Soil Amendments Part II Will adding sand improve the texture of a clay soil? Washington State University (PDF)
Manufacturers and distributors of soil conditioners and amendments available in Qld are invited to advertise on this page. For example: composts including treated wastes, wetting agents, pH adjustment, water storage additives (granules, gels), additives for drainage and porosity, flocculation agents. More information about advertising.
More about mulches and mulching practice here: Mulches
News
Biochar and earthworms get along
Reseachers have found that lack of moisture when dry biochar was incorporated into soil caused unwanted effects on earthworms. This suggests that when biochar is used in the field, pre-wetting or immediate irrigation after incorporation may be may be necessary. Fortunately, biochar was found to have no effect on the reproduction or immune systems of earthworms studied. Source: Study Finds Greenhouse Gas Reduction Strategy May Be Safe for Soil Animals (June 2011).
Biochar could help conserve water
Research at Tamworth Agricultural Institute is investigating the use of biochar on pastures. Results so far indicate potential for improving water use efficiency. Source (NSW Department of Primary Industries): Australian-first research looks at impact of biochar on water efficiency (April 2011)
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