5.3 Soil Degradation and Conservation

Reduced soil fertility

Relationship between soil ecosystem, succession & soil fertility

Influence biotic factors range from organism or bacteria to humans


  • Bacteria fix atmospheric nitrogen converting into a usable form for plant roots
  • Mycorrhizal fungi on tree roots take up soil nutrients and pass them directly to the tree
  • Decomposes break down litter releasing nutrients into the soil
  • Soil organisms help to mix the soil improving its structure
  • Animal burrows help to aerate the soil
  • Animal faeces return nutrient to the soil

Indirect influence


  • Interception of precipitation by vegetation
  • Reduction of precipitation via evaporation

Types of soil degradation

Erosion by water and wind

Factor influence water erosion
Soil with high infiltration rates - high level of organic matter - greater resistance to erosion

Factor influence wind erosion
Soil surface that are not rough and ridged offer little resistance to wind

Physical degradation

Factor

  • loss of structure, compaction
  • Caused by compaction through heavy machine or animal and cultivation in wet weather

Chemical degradation

Factor

  • Loss of nutrients or organic matter -reduce the capacity to support plant growth
  • Soil acidification - change in the composition of soil (impact of acid rain)
  • salinization - accumulate salts rise
  • Soil toxicity - caused by municipal and industrial waste

Biological degradation

Factor

  • Loss of organic matter and biodiversity (cause by fertilizer and herbicides) - reduce ability of soil aggregate - formation of soil crust - reduce water infiltration - increase run off and water erosion

Rain breakoff the soil aggregate material - lighter aggregate - easily remove by raindrop splash - runoff increase

Steeper the slope - increase the length of slope - greater accumulation of runoff

Increase vegetation - increase interception - reduce rain drop impacts - slow down the surface runoff - allow excess surface water to infiltrate

  • Lack of permanent vegetation cover - extensive erosion
  • Loose, dry, and bare soil is most susceptible

Soil Erosion

Salinization

Toxification

Desertification

Reduced soil fertility can lead to soil erosion through the loss of essential nutrients and organic matter, which provide stability to the soil structure and promote plant growth

Without these nutrients, the soil becomes more susceptible to erosion by wind and water

When soil fertility is low, plants struggle to grow and establish strong root systems

This weakens the vegetation cover, making the soil more vulnerable to erosion by wind and water

The spread of desert-likeconditions into previously green areas causing a long term declinein biological productivity

Caused by climate change and/orby destructive use of the land.

Reduce soil cover through grazing or preparing soil for planting increase wind and water erosio

,Reducing soil nutrient and damaging soil structure.

Semi arid area: Kalahari Desert

Found in marine derived sediments, coastal location. Major problem in Australia.

Hot arid areas where capillary action bring salts to the upper part of soil.

Removal of vegetation in dry land farming

This can occur when certain chemicals or pollutants, such as heavy metals, pesticides, or industrial waste accumulate in the soil

These contaminants can harm soil organisms and disrupt nutrient cycling

This happens when there is an excessive accumulation of salts in the soil

This can occur in arid or semi-arid regions where water evaporation exceeds precipitation

A process where previously fertile land turns into arid desert-like conditions

Wind Erosion

Gullying

Sheet Wash

Drier soils have their top layers consistently removed by wind.
Loss of nutrient-rich topsoil accelerates desertification.

Channels (gullies) form on hillsides after rainfall.
Gullies deepen over time, causing more soil erosion and reduced fertility.

Large areas of surface soil are washed away during heavy rain.
Can lead to landslides and further soil degradation.

Commbercial & Industrialized FPS
vs
Small Scale Subsistence Farming

More holistic approach to farming

Cropping & Soil Husbandary

relies on ecological processes, biodiversity and cycles adapted to local conditions, rather than the use of inputs with adverse effects

large amount of chemical & energy

  • alters natural environment/ deforestation
  • deteriorates soil quality
  • eliminate biodiversity
  • minimize potential crop yield
  • use of heavy machine
  • soil more impermeable
  • reduce O2 content
  • use of fertilizers
  • alters soil's chemical composition
  • increase nutrient runoff
  • use of pesticides/ herbicides
  • increase amount of dangerous toxins

Methods

Maintaining crops cover as long as possible

Keeping stubble and root of the crop after harvesting

Planting a grass crop

Grass crop maintain the action of roots binding the soil

Minimize the action of wind & rain on the soil surface

Increases organic content - allows the soil to hold more water

Soil organic matter as source of plant nutrient - improve water retention & soil structure

Important as soil buffering capacity against mant threats

Avoiding the use of Marginal Lands

  • land that has little or no agricultural or industrial value
  • little potential for profit
  • often has poor soil or other undesirable characteristics -

Cultivation gives farmer lower yields and increasing the risk of soil degradation

Soil conservation method

Soil conditioners

cultivation

wind reduction

Soil conditioners like compost, manure, and gypsum improve soil structure, water retention, and nutrient availability. Mulches protect the soil from erosion and moisture loss while suppressing weeds.

Techniques like contour plowing, terracing, and no-till farming prevent erosion and improve soil structure. Crop rotation and cover cropping maintain soil fertility and protect against erosion.

Windbreaks, ground cover crops, and mulching reduce wind erosion by protecting the soil from wind. Erosion control fabrics stabilize soil in windy areas, preventing soil displacement.

Impact of Human

Deforestation

Intensive grazing

Urbanization

(certain) Agricultural practices

Soil erosion

Soil fertility

Soil fertility

Soil fertility

Soil fertility

Soil erosion

Soil erosion

Soil erosion

reduce leaf litter & decaying plant matter that contribute to nutrient cycle, depletes soil fertility over time

trees cleared, increase rainfall intrusion @ wind erosion, making nutrient from topsoil runoff @ blown away, soil erodes

  1. remove vegetation by grazing, reduce organic matter inputs into soil
  2. soil compaction by livestock, reduce ability soil to absorb water & nutrient > decrease soil fertility
  1. trampled by livestock, breaking down soil structure & increasing soil erosion
  2. vegetation removed, vulnerable to water runoff & wind erosion, soil erodes

soil surface sealed with concrete, no organic matter input to soil, nutrient in soil decreses, soil fertility will decreases over time

roads, buildings, and other infrastructure construction seal soil with impermeable surfaces, increase water runoff to other areas cause nutrient runoff too, soil eroded

monoculture farming degrade soil fertility by depleting certain nutrients over time

  1. plowing, tilling especially on slopes, destroy soil structure, increase soil evaporation, less water retention in soil, soil erosion
  2. not managed irrigation cause soil erosion through water runoff & nutrient runoff
  3. remove protective crop cover after harvest expose soil to wind & water erosion