February 24, 2011

Improve Your Soil Organically

There are different types of soil , ranging from heavy clays to pure sand. Each of which each presents it's own challenges to the gardener. Even the best of loam soils still needs replenishing on a regular basis if it is to be used for on-going food production and even the best of soils can still be improved by nurturing the living organisms within that soil. Many descriptions of soil will list the particle size of the minerals within that soil like this:

Mineral elements:
•Clay - 002mm or smaller
•Silt - 002 mm to .05 mm
•Fine Sand - 05 mm to .25 mm
•Sand - 25 mm to 1.0 mm
•Gravel - 1.0 mm to 32 mm
•Stones - over 32 mm

But a healthy soil contains much more than just mineral particles of different sizes. It also contains water, air, organic mater and life in the forms of micro and macro organisms. Many of those organisms such as earth-worms are beneficial organisms in regard to soil health and plant growth.

Perhaps the best example of a beneficial organism in a healthy soil is a group of micro organisms called  mycorrhizae. "Mycor"-"rhiza" literally means "fungus"-"root" and describes the mutually beneficial relationship between plant roots and some fungi. These specialized fungi attach to the roots and extend far into the soil. Mycorrhizal fungal filaments (hyphae) in the soil are truly extensions of root systems and are more effective in nutrient and water absorption than the roots themselves.

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The fine fillaments of mycorrhiza form a mutually beneficial, symbiotic relationship with plant roots.


these fungii also help to protect the plant from soil borne pests and diseases and help improve the soil structure. Mycorrhizae are living organisms and can be damaged by using chemical fertilizers and pesticides, so they are much more prevalent in organic growing conditions. Poor soil management can destroy all of these soil organisms and decrease the productiveness of the land and cause deterioration of the soil structure.

Get to Know Your Soil.
As a gardener, it pays to get to know your own soil so that you can work to improve it in the most effective way. There are a few simple tests that anyone can do that will provide you with enough information to understand what the soil is like.

The Sausage Test

Collect some soil from your garden. For a tue picture of the soil,
take the soil from below the humus layer in the rootzone of your plants. Take a handful of soil and moisten it to the point where it will form a ball. Wrap your fingers around the ball and try to squeeze out a sausage between the thumb and forefinger, let the sausage bend as you form it whilst watching to see how far it can be bent before breaking.
  • If you cannot form a ball, you have a very sandy soil;
  • If you can feel larger gritty particles in the ball, you have a course sand;
  • If you can form a ball but a sausage cannot be formed without breaking, you have a sandy soil;
  • If the sausage bends a little, you have a sandy loam;
  • If the sausage will bend half way around the forefinger, you have a loam or silty-loam;
  • If the sausage bends more than halfway around your finger, you have a clay-loam or sandy-clay.
  • If you can form a longer sausage with cracks, you have a clay soil;
  • If you can form a longer sausage without cracks, you have a fine (or heavy) clay.
The best soil structure for growing most plants is a loam or silty loam as this has the best combination of moisture retention and air spaces. (Plants need to breathe through their roots.) If you think that you have a loam but are unsure if it is a clay loam or sandy loam then you can perform another simple test.

The Jar Test
The jar test or sediment test is quite simple to do and will help you to see the composition of your soil better. Just put a handfull of your soil into a jar and 3/4 fill the jar with water. Shake the jar well until all the soil is in suspension. Place the jar on a flat surface and wait to see how long it takes to settle. As the soil settles, different layers will form. Course sand will settle fastest, fine clay will settle last. (except organic matter, which may not settle at all.) By comparing the different thicknesses of the layers, you can work out the percentages of the different soil particle sizes and determine more closely your soil type.

Measure the percentages of sand,silt & clay and apply them to the soil triangle to determine your soil type.

Examine Your Soil Profile
Soils can contain different layers within the soil profile. Those layers can vary in structure and depth. As many plants can send roots up to 1 metre (3-4 foot) deep, it pays to look at the soil profile as well. This can be done by digging a small diameter hole to a depth of at least 1 metre and looking at the soil that you are removing by laying it out on newspaper or cardboard in a line. This should give you a type of core sample and any obvious differences in soil structure at different depths should be visible. If you have different layer, you can test samples from each layer to find their structure. You should also look into the hole and see if the layers are obvious, how much organic matter is visible and how deep any plant roots are penetrating.

Understanding your soil profile will tell you much about how well your soil will drain and how deep your plant roots will be able to penetrate. As the diagram shows, plant roots will be found mostly in the topsoil and subsoil. The deeper the topsoil and subsoil, the better your plants will be able to perform.
  
Testing Soil pH
All substances have a specific pH (potential Hydrogen) which is a measure of acidity or alkalinity. An acid substance is one that releases hydrogen in solution, an alkaline substance is one that removes hydrogen from a solution. pH is measured on a logarithmic scale from 0 to 14 with 0 being fully acid, 7 being neutral and 14 being fully alkaline. The pH of your soil will affect how well some plants can perform compared to others, as different plants are adapted to different soil pH. Most food producing plants prefer a soil that is slightly acid to neutral (pH 5 - 7). At higher pH levels some minerals (particularly iron) become less available to to plant roots. Soil ph can be adjusted to suit the needs of the plants that you wish to grow.

Test kits can be purchased quite cheaply from good gardening or hardware stores and testing is quite a simple proceedure to carry out. Instructions and a colour chart will be included in the kit. Once you know the pH soil of your garden it is quite easy to adjust organically. If your soil is alkaline (pH 9+), additions of  organic matter in the form of compost, worm castings, blood and bone (hoof and horn), seaweed spray or manure, or any combination of these, will help to make soil more acid. An application of trace elements in the form of mineral dust might also be required if plants are showing symptoms of mineral defficiency, such as lime induced chlorosis. If your soil is too acid it can be adjusted by applications of dolamite lime powder. Soils containing a lot of organic matter tend to be slightly more acid so small applications of lime in the form of dolamite may be needed most some crops, whereas some such as potatoes and strawberries prefer a more acid soil. Brassicas on the other hand prefer a slightly alkaline soil. Knowing the soil pH and adjusting it to suit the particular crop in a rotation system will help to boost productivity.

So now that you have got to know your soil a little better and know it's pH you can begin to improve your soil organically. Some soils may or may not need lime but all soils will benefit from the addition of organic matter. In sandy soils it will act as a medium to help hold water in the soil as well as feeding the soil and plant. In clay soils it will help the fine clay particles bind together to form larger particles and that helps create more air spaces within the soil, as well as aiding with drainage and friability. Organic matter in the soil will help to attract and increase soil life which in turn will help break down insoluble organic particles into soluble plant food. I cannot stress this enough. Healthy soils will be full of life and that life will help to improve your soils. All life needs to feed and organic matter in the soil is what soil organisms  feed upon. Continued applications of chemical fertilizers and pesticides can severly impact upon soil life which in turn can impact detrimentally upon soil condition.

If you have a soil that you consider to be too shallow or sandy or compacted to easilly repair, don't despair. Raised beds and no-dig gardening can grow food  well in any conditions, even on top of paved areas, as has been shown by Cuba's organiponicos.  A good healthy soil will grow good healthy plants that are less prone to diseases and insect attacks. Using organic methods to farm your soil will naturally improve productivity and most of the materials you will need can be produced in your own system. How easy is that?


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