Soil Properties
Soil properties influence nitrate leaching because they
determine how water moves. Farmers can not change some
soil properties (such as texture), but can profoundly influence
others (such as structure).
Soil Texture: The proportion of small (clay), medium (silt),
and large (sand) particles in a soil. The textural triangle is used
to determine the textural class.
Soil Structure: The arrangement of soil particles into stable
units (aggregates). Soil structure can range from loose and friable,
to blocky, plate like, or massive (without structure). Water
takes the easiest path through soil and primarily flows around
aggregates, rather than through them.
Water-Holding Capacity: The maximum amount of water
that can be stored in the soil is important in estimating the
potential for nitrate leaching. Sandy-textured soils cannot
retain as much water as loam-textured soils.
Soil Porosity: The space between soil particles that is occupied
with ever-changing amounts of air and water. Porosity
is determined by soil texture and soil structure. Compaction
reduces the number and size of soil pores. (Figure 1)
Soil Permeability: This property is determined by the
soil texture and the structure. The size and arrangement of the
pores determines the rate of infiltration (movement of water