Zonal soils Flashcards
what is soil made up of?
soil is made up of:
25% -air
25%-water
45%- mineral particles
5%- other including- 10% organisms
-10% roots
-80% humus
what is a zonal soil?
- a zonal soil is a soil that has distinguishable horizons and has the ability to support rooted plants
Why is soil important?
- sustains 95% of food production
-hosts more than 25% of the planets biodiversity
-plays a critical role in the carbon cycle because it is organic matter so it contains around 60% carbon and holds 1500 tonnes worldwide
-sustainable soil management can contribute to more and healthier food
-soil degradation threatens food security
what are some examples on zonal soils?
- tropical red latosol
-podzol
-Mediterranean soils
-Chernozems
-Chestnut soils
what are the features of a Tropical red Latosol?
-up to 30m deep
-top la hoyer red colour, bottom layer yellow colour
-red colour due to build up of iron and aluminium oxide
-yellow colour is a result of silica deposit
-tropical equatorial rainforests are found here and their leaf shed creates the thin top humus layer
-found 5 degrees either side of the equatorial belt
what are features of a Podzol soil?
-1m deep
-clear
-podzols are associated with coniferous evergreen trees so the top layer is usually a thin layer of pine needles
-bleached horizons going downwards as finer material is washed downwards
-they often have a hard pan layer of aluminium
the podsolization process requires a general downward movement of water through the soil. However precipitation exceeds evapotranspiration because of low temperatures.
what is soil erosion?
-soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation.
how does wind erosion occur?
-wind erosion is caused by strong winds that physically move lighter, less dense soil from the nutrient rich top soil.
What is an example of wind erosion?
-During the 1930’s, The American Mid -west was hit by a giant dust storms which caused catastrophic wind erosion. this erosion was not solely the result of sequential drought but also due to the removal of the natural grassland.
what is water erosion?
-water erosion occurs when rain or snow melt displaces the water flowing over the land so washes away the top nutrient layer of soil. Caused by rainfall, runoff ,melting snow or ice and irrigation.
how can you prevent water erosion?
-planting and harvesting across a field rather than up and down to reduce chance of a channel forming on a gradient.
what is waterlogging of soils?
-soils become waterlogged when water is unable to drain away. This leaves no air space in the saturated soil and plant roots literally drown. Waterlogging is common in naturally poorly drained soils or when heavy soils are compacted, the aerobic environment causes root tissue to decompose and if not addressed plants will die.
why is waterlogging of soils a problem in hot areas?
-In hot climates, waterlogged soils provide breeding grounds for Mosquitos which transmit diseases such as Zika virus, dengue fever, yellow fever, encephalitis and malaria.
what are the causes of waterlogging?
-rainfall exceeds the rate at which soils can absorb or atmosphere can evaporate
-gentile relief restricts throughflow of infiltrating soil water
-relief basins or depressions encourage accumulation of water
-seepage from rivers canals and reservoirs infiltrated soils
-soils include an impermeable clay layer of iron pan
-excessive irrigation water is used to flood fields.
what is salinization of soils?
-Over long periods of time, soil minerals weather and release salts. Additional salts are deposited via dust and precipitation. In areas of sufficient precipitation or efficient irrigation these salts are leached out of soil and infiltration and percolation so increasing salinity in the soil. Poor drainage leads to water logging, bringing dissolved salts to the surface so when the water evaporates, a layer of salt is left on the surface, compounding the degradation. only salt tolerant crops such as cotton can withstand the salt. If salts are alkaline, and PH rises above 11 plants become infertile. If salts are acidic and soil PH falls below 4 plants cannot absorb nutrients so crops fail. Either way crops fail.
what is structural degradation of soils?
-This is referring to the compaction, the compression of soil particles so that spaces between them diminish but can also refer to the lack of cohesion that occurs in sandy soils. If too compact, it can be difficult for air, water and roots to move through and therefore can be difficult to grow crops.
what is soil management?
-soil management is all about conservation. Simply meaning preserving and protecting vegetation cover, essential on steep slopes means on forest, orchards, vineyards or pastures.
What is the best long term solution for soil erosion?
-afforestation and reforestation are the best long term solution for soil erosion because once the trees have grown, their foliage shades from the sun, intercepts rainfall and their roots bind the soil together.
what are some examples of soil management?
-terracing- shaping land in steps to control erosion
-contour ploughing- ploughed along contour, improves water distribution
-crop rotation and cover crops- vary crops grown in a year
-strip cropping- crops sewn in alternate strips to prevent erosion
-direct drilling- sowing crops directly into previous crop stubble
-selective afforestation with shelter belts
-improved drainage to prevent water logging and salinization
-careful management of irrigation to reduce the risk of water logging.
