Sand
Origin
Sand is a name for a group of granular materials
consisting mainly of quartz. The size of the different particles is in
between 0.05 and 2 mm. In the Netherlands mainly sand originating from
rivers is used. Sand from the dunes can't be exploited anymore. For the
production of asphalt special sand is produced �brekerszand'. For this
product pebbles are crushed until the material has a uniform fraction distribution.
Characteristics
Sand products are heavy, have a small water buffer and
in thin layers a low air content. This is mainly caused by the fact that
sand has only a small amount of pores. Soil fits also in this category
and is not suitable as a growing medium. The main problem is again the
low air content if used in thin layers. If sand is used, a coarse type
is preferred. Another problem is that sand can't be bought in a certain
fraction, at least not for reasonable prices. The fraction distribution
will vary from one batch to another. Because the fraction distribution
determines the air content this parameter will vary too. A product with
a constant quality can't be guaranteed. �Brekerszand' doesn't have this
quality problem.
Sand is inert. The pH and EC will vary depending on the
lime content. Sand has been used as an inorganic media component to add ballast to containers. Some sands contain calcium carbonate which may raise media pH undesirably. A rise in pH may lead to nutrient deficiencies, particularly of minor elements such as iron and boron. A few drops of dilute hydrochloric acid or strong vinegar may be added to sand to test for carbonates; if bubbling and fizzing result, carbonate is present as a result of carbon dioxide production. Sand used for container media should have a 6 < pH < 7. Sand maintains good drainage, a low water-holding capacity, and a high bulk density when used independently of other materials. Because of its shape and size, sand can obstruct pore spaces, decreasing drainage and aeration, instead of improving porosity.
Durability
Sand is durable because it is not significantly influenced
by chemical and biological factors during growing plants. Sand can be steamed
very well. If sand is used in thin layers and the material is steamed pores
will be filled with water in no time. This will make the steaming process
more complicated. Sand can't be composted. As a waste material it can perhaps
be used for road construction.
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