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Old February 23, 2015   #5
NathanP
Tomatovillian™
 
Join Date: May 2013
Location: RI
Posts: 183
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The site at the below link is probably worth reading in it's entirety. FAQ#7 applies most directly.

Quote:
7. How does biochar affect soil properties like pH and CEC? Biochar reduces soil acidity which decreases liming needs, but in most cases does not actually add nutrients in any appreciable amount. Biochar made from manure and bones is the exception; it retains a significant amount of nutrients from its source. Because biochar attracts and holds soil nutrients, it potentially reduces fertilizer requirements. As a result, fertilization costs are minimized and fertilizer (organic or chemical) is retained in the soil for longer. In most agricultural situations worldwide, soil pH (a measure of acidity) is low (a pH below 7 means more acidic soil) and needs to be increased. Biochar retains nutrients in soil directly through the negative charge that develops on its surfaces, and this negative charge can buffer acidity in the soil, as does organic matter in general.
CEC stands for Cation Exchange Capacity, and is one of many factors involved in soil fertility. “Cations” are positively charged ions, in this case we refer specifically to plant nutrients such as calcium (Ca2+), potassium (K+), magnesium (Mg2+) and others. These simple forms are those in which plants take the nutrients up through their roots. Organic matter and some clays in soil hold on to these positively charged nutrients because they have negatively charged sites on their surfaces, and opposite charges attract. The soil can then “exchange” these nutrients with plant roots. If a soil has a low cation exchange capacity, it is not able to retain such nutrients well, and the nutrients are often washed out with water.
See Chapter 14: Biochar effects on soil nutrient transformations; Chapter 15: Biochar effects on nutrient leaching; and Chapter 16: Biochar and Sorption of Organic Compounds, in Biochar for Environmental Management: Science and Technology, edited by Johannes Lehmann and Stephen Joseph, Earthscan 2009.
http://www.biochar-international.org/biochar/faqs#q7

Some information on my background, I was into fishkeeping and planted aquaria for many years prior to getting back into the outdoor plant and gardening hobby, and having a substrate (soil) with high CEC is one of the most important factors in growing aquarium plants. It stands to reason that would be true with mostly any soil. Depending on what the soil is like in different locations, biochar might be more or less effective than in other locations.

Last edited by NathanP; February 23, 2015 at 10:19 PM.
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