Soil provides support and nutrients for plant growth
Pedosphere Intersection of four spheres Hydrosphere Lithosphere Biosphere Atmosphere
What is the Pedosphere? The envelope of the Earth where soils occur soil forming processes are active
Factors affecting soil formation Climate (precipitation, temperature) Vegetation (plants) Parent material (geological/organic) Organisms (soil microbes/fauna) Relief (configuration of surface)
EROSION – Starts the process of soil formation is the movement of sediment and rock to new places.
Weathering breaks down rocks to create soil. It can be caused by weather, water, or living things
Animals making burrows in the soil help bring air and water into the soil
Soil organisms are involved in nearly every aspect of soil quality Organic matter Nitrate Leaching Soil Community Nutrient cycling Structure/Aggregation Humification Decomposition
There are five components of soil: 1. Rock 2. Sand 3. Silt 4. Clay 5. Humus Can you match each type of soil to its picture?
Soil is made up of mineral grains. Water is held between the grains in the pore spaces. 25% of the soil is air. Oxygen is essential Organic matter is both coarse and fine. Bacteria- A thimble of soil can contain 2 billion bacteria, 30 million fungi fragments and 100,000 single cell plants and animals.
Soil texture Percentage of sand, silt and clay Size ranges of sand, silt and clay Hand and laboratory methods Texture triangle Example: Clay Loam
Soil Texture Affects aeration Affects water holding capacity Affects pore space
Sandy particles are the only particles which may be large enough to be seen with the naked eye. Predominantly sandy soil has a gritty feel (coarse-textured) when rubbed between the fingers. Silt particles are smaller than sand particles. Predominantly silty soils feel powdery (like flour) and do not hold together well when wet, though they are more cohesive than sandy soils. Clayey soil has the smallest soil particles, and many small pore spaces. Soils with a high number of clay particles have a very high water holding capacity and are very fine-textured, making them feel smooth and sticky (like soap) when wet. Loam is the best soil texture for growing things. It is a mixture that has useful amounts of clay and silt in a base of sand.
Sand (largest particles more than 40 micrometers) Sand is tiny grains of worn down rock. It doesn’t hold water or have many nutrients.
Silt (2 – 50 micrometers) Silt is very small, broken pieces of rock. It is larger than clay, but smaller than sand. It is powdery when dry. Sand ------------Silt---------------Clay (smaller particles)(larger particles)
CLAY (less than 2 micrometers) Clay holds water well. It is sticky and can be shaped when it is wet. But, it is very hard when dry. Clay has many nutrients. Clay is used for adobe or brick houses.
Coarse-textured soils have a high sand content. They consist of large particles with uneven surfaces and because of this, have large pore spaces These traits make such soils loose and easy to work; however, the large spaces do not retain water or nutrients. Water infiltrates sandy soil and percolates (moves through it) quickly and easily. As a result, sandy soils are generally dry and infertile. The dryness of sandy soil contributes to a shortage of nutrients because of less vegetative growth and, therefore, less organic matter is produced.
Medium-textured soils known as loams, have properties in between those of coarse and fine texture. Silty loams to sandy-clay loams have a good capacity to retain water without becoming waterlogged. They are easy to work and form good clumping mixtures during cultivation. Loams contain a good supply of nutrients, necessary for the organisms living in the soil. Loam or silty soils have a texture which is most suitable for the greatest variety of living organisms.
Fine-textured soils range from silty clay to heavy clay. Heavy clays are like soft plastic when wet and are hard when dry. This makes them difficult to work. Clays are often waterlogged and poorly aerated, as well as being cool. Clay soils absorb and release water (to plants) very slowly. Air movement within the soil is also very slow. These conditions mean that clay soils take longer to warm than coarser soils. A lot of water in the spaces can mean little air is available for living organisms to carry out cellular respiration and certain biochemical actions.
Fertile soil contains nutrients. There are major nutrients and micro nutrients. Major nutrients make up the bulk of the nutrients in your soil. The most important major nutrients are :Nitrogen, Potassium and Phosphorus. Other major nutrients are :Calcium, Magnesium and Sulfur. Micronutrients are: Manganese, Iron, Copper, Zinc, and Boron. Nutrients need to be balanced and available to the plant's roots. Organic matter is key to helping maintain this balance.
Humus Humus is made of leaves, twigs, small animals, or other decayed substances. Humus adds many nutrients to the soil. Humus is in the topsoil.
3 Layers of Soil 1.Topsoil (The layer on TOP) 2.Subsoil (The prefix SUB means under) 3.Bedrock (It’s hard as rock down there!)
Soil Porosity The percentage of soil that is a pore space or void. The average soil porosity is 50% and the holes are filled with air or water depending on the moisture content Sands have larger pores but less total pore space than clay.