Answers

2014-01-08T12:07:44+05:30
SAND  These are large particles (2mm - 0.02mm) formed by the physical break-up (weathering) of rocks, i.e. fragments of rock.  Sands have small surface areas and have an almost negligible role in the chemical activity of the soil, i.e. they are chemically insert or inactive.  Sand acts as the framework for the active particles, i.e.: silts (fine) and clay.  Sand does not hold much water because the particles act as single grains.  In a soil the sand particles affect the size of voids. They tend to increase the size of the voids allowing freer movement of water and air. Therefore, sandy soils are well drained and well aerated.  Sands are easily warmed because they are will aerated and do not retain much water.  Sands do not compact under weight.  Having little ability to supply or hold plant nutrients, the native or added nutrients are readily lost by leaching (downward movement of water through profile). Because of these properties, there is little plant growth in pure or nearly pure sands. It follows that the return of organic matter is small in amount and is readily broken down or lost.  Sands can become productive mediums for plants, if water and nutrients are amply supplied. Organic matter will build up in quantity, improving the moisture and nutrient holding capacity with efficient husbandry.   SILT  Silts are formed by physical weathering.  Coarse silts are chemically inactive.  Finer silts, which approach colloidal sizes, may exhibit some of the characteristic properties of clay.  The particles adhere to one another, and have a large surface area giving them a capacity to hold some water and nutrients. 
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