Soil Properties
Texture is determined by the percentages (by weight) of sand, silt of clay that it has. Particles larger than 2 mm in diameter are called gravel or stones and are not considered soil because they do not have any direct value to plants.
Sand has the largest soil particles. They range from .05- 2 mm in diameter and are easily visible to the eye. Silt is considered medium sized and ranges from .002 - .05 mm. Silt can be conpared to flour particles and are barely visible to the eye. Small particles include anything less than .002 mm in diameter and are referred to as clay. These individual particles can only been seen under an electron microscope.
A soil's texture affects many of its properties and in turn, plant growth.
Soil minerals are often present as ions (charged particles). Clay particles have a negative charge on its outer surface that attracts and binds with positively charged ions. These would include potassium and magnesium, both of which are essential for plant growth. Negatively charged minerals will not bond with the clay and are often washed out of the root zone.
A loam is considered an ideal agricultural soil. It has an optimum combination of soil particle sizes (40% sand, 40% silt, and 20% clay). The larger particles provide structural support, aeration and permeability to the soil. The smaller particles bind together and hold nutrient minerals and water. Soils with large amounts of sand do not hold enough minerals or water to be desirable for plants. Soils with too much clay are also bad because they do not allow enough drainage or provide enough oxygen. Clay soils also tend to get compacted and do not allow enough pore spaces for air and water.
Sand has the largest soil particles. They range from .05- 2 mm in diameter and are easily visible to the eye. Silt is considered medium sized and ranges from .002 - .05 mm. Silt can be conpared to flour particles and are barely visible to the eye. Small particles include anything less than .002 mm in diameter and are referred to as clay. These individual particles can only been seen under an electron microscope.
A soil's texture affects many of its properties and in turn, plant growth.
Soil minerals are often present as ions (charged particles). Clay particles have a negative charge on its outer surface that attracts and binds with positively charged ions. These would include potassium and magnesium, both of which are essential for plant growth. Negatively charged minerals will not bond with the clay and are often washed out of the root zone.
A loam is considered an ideal agricultural soil. It has an optimum combination of soil particle sizes (40% sand, 40% silt, and 20% clay). The larger particles provide structural support, aeration and permeability to the soil. The smaller particles bind together and hold nutrient minerals and water. Soils with large amounts of sand do not hold enough minerals or water to be desirable for plants. Soils with too much clay are also bad because they do not allow enough drainage or provide enough oxygen. Clay soils also tend to get compacted and do not allow enough pore spaces for air and water.