Presentation on theme: "Soil is the growing medium for our food Without it we could not survive Soil purifies our waste Soil is home to plants and animals It may take up to 100."— Presentation transcript:
Soil is the growing medium for our food Without it we could not survive Soil purifies our waste Soil is home to plants and animals It may take up to 100 years to form one inch of topsoil We are losing so much soil to erosion each year that the lost soil if loaded into dump trucks parked back to back would extend to the moon and back. An earthworm can work a ton of soil a year
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.
Animals making burrows in the soil help bring air and water into the soil
D Humus gives the topsoil a rich brown color Leaching takes minerals carried by water to the subsoil
In a mature soil profile, there are three distinct layers(horizons) of the soil. The undisturbed rock below the soil is called the bedrock. The Ao-horizon consists of the highly decayed organic material referred to as the peat and humus. Humus gives soil horizon A a rich brown color.We see no such brown layer in the Pine Barrens.
In the A horizon, water percolates downward and carries minerals as it goes. This is called “leaching.” Leaching carries minerals down into the lower soil horizons.
The B-Horizon is called the subsoil. This horizon is where the leached minerals from horizon A end up. These leached minerals may color the subsoil. For example, the presence of iron my color the subsoil red. Horizon B-Zone of Accumulation of leached minerals
The C-horizon is called the zone of weathered bedrock. When you have a residual soil, one formed over the original bedrock, the C-horizon resembles the bedrock, but it is weathered. In a residual soil, the bedrock is below the C-horizon. Remember that the Coastal Plain does not have bedrock under the soil profile, but it has layers of sand, clay and gravel. That is because of the sea level changes over time and the rivers that flowed over it.
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.
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.