soils

• soil components-

  Mineral matter

  Dead organic matter

  Water

  Air 

  biota
• living organisms are involved in many soil processes that affect soil fertility:

  detrivores break up dead organic matter and release nutrients into the soils

  they can also aerate the soils making decomposition faster

  decomposers break up the dead organic matter by secreting digestive enzymes

  nitrogen fixing bacteria converts gaseous nitrogen into ammonium ions

  nitrofying bacteria oxidises ammonium ions to nitrite ions and then nitrate ions

  mycorrhizal fungi form symbiotic relationships with plant roots and aid phosphate uptake by the plants.
• what lives in soil that help creates nutrients

  Biota- N fixing bacteria(soil), n-fixers (rhizobium), aerobic decomposers (bacteria), Nitrifying bacteria, mycorrhizal fungi, earthworms 

  Dead organic matter- leaves
• factors affecting soil fertility

  Aeration

  Water content

  Organic matter content

  Soil texture

  Biota

  Depth

  Thermal capacity

  pH

  Soil structure
• Soil texture is the size of the mineral particles found in the soil and refers to the amount of clay, silt and sand particles.

  Sand- the grains are bigger and there is more space for water to infiltrate into the soil

  Silt-full of nutrients 

  Clay- flat molecules- keeps hold of the water better-won’t drain through as quickly

  Have a negative charge- attract the cations- zinc, magnesium, iron

  Sand is the biggest and clay is the smallest 
• link between dead organic matter and soil erosion


  Lots of d.o.m. worms digest material and produce hummus-chelates-sticky stuff on hummus-more aggregation-the heavier it becomes-sticks together-less likely to be washed away.
• human activities causing soil erosion

  deforestation

  cultivationg steep slopes

  over-grazing

  soil compaction

  reduction of soil organic matter content

  ploughing of vulnerable soils

  reduction of soil biota
• environmental impacts of soil erosion

  sedimentation in rivers, reservoirs and coastlines

  downstream flooding

  increased atmospheric particles

  desertification

  landslides

  reduced productivity
• solutions to soil erosion

  cultivation of long term crops

  contour ploughing

  terracing

  create windbreaks

  use multi-cropping

  use strip cropping 


  Soil conditioning and using increased organic matter
• Detrivores


  Organisms that break down dead organic matter into smaller pieces, releasing nutrients into the soil and aerating the soil to speed up decomposition.
• Nitrogen-fixing bacteria


  Bacteria that convert gaseous nitrogen from the air into ammonium ions, which can be used by plants as a source of nitrogen.
• Decomposers


  Organisms that secrete digestive enzymes to break down dead organic matter into even smaller particles, releasing even more nutrients into the soil.
• Nitrifying bacteria

  Bacteria that convert ammonium ions into nitrite ions, and then into nitrate ions, which are a form of nitrogen that plants can easily absorb and use for growth.
• Mycorrhizal fungi


  Fungi that form symbiotic relationships with plant roots, helping them absorb phosphorus from the soil, which is an essential nutrient for plant growth.
• Sand


  The largest mineral particles in soil, with grains that are visible to the naked eye and allow for greater water infiltration.
• Silt

  Mineral particles in soil that are smaller than sand, full of nutrients, and have a smooth, flour-like texture.
• Clay


  The smallest mineral particles in soil, with a flat, plate-like shape, a negative charge, and a high water-holding capacity.