Soil

Components of Soil The four components of soil are minerals, organic matter, air, and water The minerals come from rocks that have been broken down into tiny particles Organic matter is called humus and comes from the decay and waste products of living things and provides nutrients for plants Between the minerals and humus are small spaces called pores containing air and water

Components of Soil Soil supports many organisms other than plants Fungi, insects, worms, and bacteria live in the soil and help decompose the organic matter

Soil Layers Soil is made up of a number of layers The top layer is the litter, made of partially decomposed material. It reduces water loss and limits temperature changes The second layer is the topsoil, made of minerals and humus. It is rich in nutrients, oxygen, and water, allowing plants to grow. Topsoil appears black because of the humus

Soil Layers The third layer is the subsoil, made of more minerals and less organic matter than topsoil. It is lighter in colour due to lack of humus The bottom layer is the bedrock, made of solid rock Litter Topsoil Subsoil Bedrock

Soil Nutrient Cycles Soil health is important to ensure the plants will grow and ecosystems will be maintained The amount and availability of nutrients is the number one factor in keeping soil healthy Nitrogen, phosphorus, and potassium are the most important nutrients These nutrients are cycled in ecosystems through producers, consumers, and decomposers

Soil Nutrient Cycles When crops grow on farms, some of the nutrients are stored in the plant tissues and removed from the ecosystem Nutrients have to be returned to the original soil, or it will gradually run out of nutrients

Fertilizers Fertilizer is any substance that helps plants grow Using fertilizer is the most common method used to replace nutrients Natural fertilizers such as manure can be mixed into the soil Synthetic fertilizers go through chemical processes, but have the same nutrients They can be sprayed or spread on fields and nutrients are immediately available Synthetic fertilizers increased both food production and farm profits

Environmental Impact Fertilizers can alter the organisms that are found in the soil The soil may have less organic matter that naturally supplies nutrients and the soil will become dependent on fertilizers, which is not sustainable During heavy rains or spring thaw, fertilizers can flow into aquatic ecosystems Excess nutrients in water causes algal blooms that reduces oxygen, leading to death of fish and other organisms

Soil Pores Soil needs pores to allow water and nutrients to pass through Oxygen is provided to plants through pores If soil is compacted too much, plants won’t grow well and water won’t drain properly