Tuesday, April 10, 2012

HEALTHY SOIL


HEALTHY SOIL: Is probably the single most important factor contributing to the health of all vegetation. If you do nothing else for your garden than to improve its soil it will be time and money well invested.

I will look at each one of these in more detail defining what it is? why it is important? How to test it? and how to correct it.





SOIL TEXTURE: Is one of the most important things to know about your soil. Soil is comprised of different sizes of mineral particles. The relative amounts of each of these different sized particles constitute a soils texture. There are 3 main soil textures; sandy, silty or clayey and there are pluses and minuses to each  one.

  • Sandy Soils: Have a gritty texture. Their larger particle size serves to create larger spaces between particles and this translates to faster drainage and easy root penetration. Sandy soils are easy to work, do not clump, are quick to warm up in the spring and can be cultivated when wet. Their excellent drainage also helps to keep plants relatively free from soil borne diseases. On the down side they do not hold water and nutrients well and require more frequent fertilizing and watering.

  •  Silty soils: Have a silky feel to them and like sand do not clump, but this consistency puts silty soils at high risk of erosion. They are slower to warm up in the spring and are harder to cultivate when wet. On the positive side they are fairly easy to work and hold nutrients and water better than sand.

  • Clay soils: Are almost cement like when dry. They are very slow to drain and should never be cultivated when wet. These soils compact very easy and are difficult to work. On the up side they are excellent at holding in water and nutrients and require less frequent watering and fertilizing.

  • Loam: Is the technical term used to describe the ideal soil texture.
It consists of a mixture of 30-40% sand……30-40% silt……..and 8-28% clay.
This mix provides good aeration, excellent drainage, is easy to work and will hold nutrients well. Unfortunately loam rarely occurs on its own.
  
How to test your soil:
To quickly identify a sandy, silty or clayey soil, squeeze a handful of moist dirt in your hand. If it makes a ball then you are not sandy, but if that ball does not easily crumble apart then you likely have a clay soil. For a much more informative test try the glass jar test.

Get a container and collect a small sample of soil from various parts of your yard. (To do this dig 5-6 small holes aprox. 6” deep. Then cut a long slice of soil from the side of each hole.)

Mix this soil together and add about 1c. of this soil mix to a glass jar, removing any pebbles, sticks, or plant parts.

Fill the remainder of the jar nearly to the top with water and shake or stir well.

Set the jar in a place where it will not be disturbed and allow it to settle for 24 hours.

You will notice definite layers beginning to form. The bottom layer will be sand (the heaviest particles). The middle layer will consist of silt and the top layer will be clay (your finest particles).

To calculate the percentages of each layer, measure the height of each layer; divide the total height into the height of one layer; multiply your result by 100. If the jar on this slide where to be measured and calculated the results would probably indicate about 60% sand; 20% silt; and 20% clay, making it a sandy soil.

The most effective way to improve your soils texture is to add plenty of organic matter. Organic matter helps sandy soils to retain moisture and nutrients; for silty soils it helps the soil to stick together better reducing erosion; for clay soils it helps to improve aeration and drainage.


SOIL STRUCTURE: Deals with how a soil hangs together. Ideally you want loose crumbs and clods. If you were to squeeze a handful of soil in your hand it should form a loose ball, but with a light tap it should easily break apart. This type of structure provides adequate porosity, no matter what your soil texture is. Soils with good structure are able to absorb more rain water, drain freely and roots and soil organisms are able to move through the soil with greater ease.

A synergistic partnership between organic matter and soil organisms is the main agent behind good soil structure. As organic matter is broken down by earth worms and soil microorganisms, small air pockets are created in the soil. Additionally the decomposing matter is turned into gelatinous substances that serve to gently hold soil particles together. Another contributor is plant roots and fungi that serve to push soil particles together as they push through. They also manufacture gummy substances that help to hold particles loosely together.            

Other tips for creating and maintaining good soil structure include: Cultivating the soil only when moist (not wet); Applying a layer of mulch to prevent compaction from pounding rains; minimizing roto tilling and other forms of cultivation, both of which will kill off many of your soil organisms and break up the desirable soil crumbs; add compost and/or manures regularly, even growing green manure is beneficial to your soils structure. (Green manure is a crop grown for the primary purpose of turning it under to supply the soil with organic matter.)


How to test your soil

The best way to test your soil is to grab a shovel and dig a hole about 1’ in depth. Carefully examine the soil. Does the soil that was removed consist of small ½” crumbs and do larger clumps break apart easily. This would indicate a good soil structure. Is the soil easy to dig or is it crusted on the top or very compacted lower down. This would indicate poor soil structure.

Another test you can perform that helps to determine the stability of your soil (stability referring to how well the soil crumbs remain crumbly); is to place a handful of soil into 2 glasses. Then gently pour water into one of the glasses to cover the soil. If the crumbs hold together when wet you have a stable structure.




Now that you have determined the texture and structure of your soil you are ready to begin amending and improving it.
Soil amendments are not fertilizers (although some do have fertilizer value). Fertilizers supply nutrients, while amendments serve to improve the soils structure, drainage and  aeration as well as improving nutrient and water retention.
One thing to be thing to be aware of when choosing a soil amendment is its pH level. Like your soil, soil amendments are either acidifying or alkalizing.  If your soil has a high pH (in other words is highly alkaline) you would not want to add wood ashes, which also has a high pH. Rather you would want to choose a more acidic amendment like compost or peat moss.
A few of the soil amendments available to you are:
§ Compost (decomposed plant material) (usually slightly acidic)
§ Shredded tree bark ( slightly acidic)
§ Sphagnum peat moss (acidic)
§ Manure (sheep, cow, horse, rabbit, even chicken) (sheep manure tends to be slightly acidic while horse, cow and chicken manure tends to be alkaline).
§ Leaf mold (acidic)
§ Wood ash (highly alkaline)
§Pine needle (acidic)
THE IMPORTANCE OF SOIL pH
What is pH?
The small “p” stands for potential and the capital “H” stands for Hydrogen. It pertains to a soils acidity or alkalinity. In some gardening books you may see soil described as being sweet or sour. Sweet soil means a soil is alkaline where as a sour soil means it is acidic.
Why is pH important to plant health?
A soils pH is of paramount importance. It affects soils fertility by controlling how well nutrients are dissolved. You can fertilize all you want but if your soils pH is out of range your plants will be unable to access or utilize that fertilizer.
Also while plant nutrients are being rendered insoluble, toxic elements become more soluble and can potentially kill plants or severely damage roots.
In addition, beneficial soil bacteria will not grow in either highly acidic or highly alkaline soil and without the help of these guys your soils structure will be poor.
Symptoms of excessively high or low pH include plants exhibiting yellowing leaves, lack of proper growth and flowering and in severe cases death of the plant.
Certain plants thrive in an acid soil while others prefer a more alkaline environment. Knowing what your soils pH level is will help you to choose suitable plants for your soil. It will also help you to correct any imbalances before they become a real problem.
Determining your soils pH
For the typical small scale home gardener a simple do-it-yourself kit will usually suffice. Available from Vigoro and CIL many garden centers now carry them. Collect a soil sample (as described earlier). Follow the instructions provided with your kit.
Alternately you can use litmus paper. Dip the tip of your litmus paper into a bit of garden soil that has been mixed with distilled water. As the paper changes colour compare it to the colour chart provided.
There is also pH meters available for purchase. They are simple, portable and use electrodes to measure the hydrogen ion activity.
Other simple home tests include using vinegar or baking soda to test soil pH. Alkaline soil will fizz when vinegar is added and acidic soil will fizz when baking soda is added.
As with all other forms of soil testing you can have your soil professionally tested at a laboratory. This is recommended especially for commercial or larger scale gardens.
Altering your soils pH
A pH level of 7 is considered neutral but as already mentioned most plants perform best at a pH level between 6.3 and 6.8.
To raise the pH level of an acid soil add calcium carbonate, ground dolomite limestone or wood ashes and switch to fertilizers and amendments that do not acidify the soil.
To lower a soils pH add agricultural sulphur or pine needles. Add organic matter and switch to acidifying soil amendments and fertilizers. It would also be wise to test for salt problem and treat any you may incur.
Note:  Add your pH amendments to the soil about 1 month prior to fertilizing and well in advance of planting. Retest after 1 month. If the pH is still too high or low give the soil a second treatment (never apply more than the manufacturers recommended amount at one time). It can take years to drastically alter the pH level of a soil. You will need to regularly test and amend your soil, if its natural pH is quite different from the one you are attempting to create.
DENTIFYING & CORRECTING PROBLEM SOILS
Some soils have special challenges to face that go beyond texture, pH imbalances and nutrient deficiencies. Failure to address these issues will usually result in poor plant health even death.
HARDPAN:
Hardpan is an impervious layer of soil at or near the soil surface. Roots, nutrients and water can barely (if at all) penetrate it. It is a difficult condition to overcome but with some hard work, patience and diligence you can greatly improve your soils structure.
Hardpan differs from soil compaction in that hardpan consists of a thin compacted layer within looser soil.
To correct soil compaction and hard pan start by incorporating a generous amount of organic matter into the soil. For your garden beds, double digging and planting a green manure crop can be helpful. If hard pan is present you will likely need a broad fork to first loosen the hard pan. If the area you are trying to improve is lawn, have it professionally aerated and sprinkle well screened compost on the lawn area yearly to increase the soils organic content.
Most importantly do not walk on your soil when it is wet or operate any type of machinery on it including a lawn mower. Allowing the children to run through the water sprinkler on a hot summer’s day will only exasperate the problem.

POOR DRAINAGE:
When drainage is slow water replaces air in the soil. Air is vital for root growth and overall plant health. To test your drainage, dig a hole about 1’ deep and 1’ wide. Fill it to the top with water and measure the amount of time it takes to drain. If the hole empties in an hour or less your drainage is good. If it takes longer you will need to take steps to improve the drainage. This is called the percolation test.
Adding organic matter and gypsum will greatly improve a soil’s drainage. If the condition is more serious you may need to install drain pipes or tile beneath the soil surface in order to carry excess water away from the area.



EXCESS SALTS:
Excessive salts in the soil can stunt plant growth, burn foliage, even kill plants. Salt leaves a visible white deposit on the soil surface. If your problem area is covered in grass it is a little harder to spot but you will know by the symptoms.

To correct the problem (or at least help) add gypsum to the soil and water the area with a deep slow watering in order to flush the salt out of the root zone.

 NUTRIENT DEFICIENCIES:  Check out this link for more detailed information pertaining to soil nutrients. http://www.blogger.com/blogger.g?blogID=435495354707620121#editor/target=post;postID=170876862352794536

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