Soil and all that gritty stuff – part 2

farming-in-the-city-logo 1 

Right now you have an idea of what your soil is made up of, there is one more test that needs to be performed.  This is a bit complicated so I hope I have explained it ok.  I could just copy and paste my soil essay, but it is over 60 pages!  So I will do my best to complete this in one page….

If you have never grown food in your soil before, a pH test is always a good idea as sometimes soils can be too acid (sour) or too alkaline (sweet)  and this will cause the nutrients within the soil to become ‘locked up’ and you will be left scratching your head trying to figure out why nothing will grow –  When you are sure the plants have been well fertilized and watered regularly.  (Yep been there done that!)

What the heck does ‘locked up’ nutrients mean?  To understand this we need to look at the pH scale. 

phscale

An ‘ideal’ soil should sit at about 6.5 – 7, this is considered neutral.  Not all soils will naturally sit  exactly at 6.5 – 7, this is just considered to be a guide.  Generally soils should fall between 5.5 and 7.5 for optimum growth.   When the pH starts to move in either direction the way plants grow can be effected, roots can be burnt, plants look nutrient deficent and production of new growth stunted.  This can be seen by looking at the diagram below. 

ph20scale20with20nutrients

At the centre of the chart is the neutral point of pH.  If you run down that line, it can be seen that the nutrients are listed.   At this point the nutrients are all freely available.  (The thicker the line the more they are available)  However move to the acid side of the scale and certain nutrients are lesser available, the same for the alkaline end of the scale.  

Why do the nutrients become available or unavailable?  This has to do with the amount of  ions in the soil.   They are tiny things that hold or repel nutrients, within the soil, at bit like magnets.  This is called ion exchange.  I won’t go into this any further, it took me fortnight of horticulture classes to learn about the exchanges.  *yikes*  More information can be found in Growing Media by Kevin Hanreck & Neil Black.

How can pH be corrected?  Two words, organic matter.  This is the life blood of all soils.  Sand will often repel water until organic matter has been added, clay will form rocks when it dries out.  Add an organic matter such as gypsum and it will become harder for it to form a crust when it dries out.  Other products can be added  and I will cover them next time.

By ensuring from the start that your soils pH is within the desired range, it will make the gardening just that little bit easier.  So just start by testing your soil.

Part 3 – adjusting your pH. 

Images From: http://broadroot.com/content/green/multirOOting2.html  &  http://www.agr.state.nc.us/agronomi/obfig21.htm

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