Soil Structure Action movie

Soil Texture Mineral Portion of Soil is made up of 3 different sized particles Most soils are a mixture of these, therefore a soils texture depends on the relative proportions of sand, silt, and clay particles. Most soils also contain larger particles, but those aren’t considered in a soils texture

Soil Texture Finger Test Moisten soil and rub it between your fingers Sandy soils are gritty and fall apart easily Silty soils feel a little slippery like baby powder Clay soils feel sticky and can be rolled into a ball easily Loam: Soil that has fairly equal proportions of sand, silt, and clay Ideal for agriculture Sand particles provide good drainage and air supply The clay retains the water and supplies nutrients Silt particles help to hold the sand and clay together

Soil Triangle

Soil Texture

Porosity, Permeability Porosity: The amount of space between particles Permeability: The ease at which gases and liquids pass through Clay soils have lots of micropores Results in lots of pore space, but low permeability The water adheres the clay surface Also locks dissolved minerals between pores making it hard for plants to access (high mineral content yet low fertility) Sandy soils have fewer macropores Less total space Pores are too large for adhesion and therefore have a high permeability

pH Soil Acidification Soil Acidification and the Economy Clay soils also tend to be more acidic As more water is absorbed, the clay fills with hydrogen ions Also reduces ability to store other positive ions and minerals are lost through leaching The reduction in pH also makes toxic ions available to plants like iron and aluminum Soil Acidification and the Economy In Northern Europe acid rain has turned the soil acidic, making more aluminum and iron available, causing damage to forestry industry through needle death

Soil Sustainability Fertile Soil is a NON renewable resource? NPK Formation takes a long time Soil use often exceeds soil formation NPK Fertile soil contains enough nutrients for healthy growth Nitrates, phosphates, and potassium are the major ones There are many micro nutrients as well Nutrients can be leached out of soil, or are removed when crops are harvested Normally nutrients return to the soil via decomposition Must be replaced for agriculture