1 Climate Relief Vegetation SOIL FORMATION Drainage Parent Material Study the diagram below.Describe the influence of the various soil forming factors on the formation of a Podzol soil.ClimateReliefVegetationSOIL FORMATIONDrainageParent MaterialSoil Biota
2 Relief Vegetation Climate SOIL FORMATION Drainage Parent Material Cold, wet climatesThin: Weathering is slowThin layer of humus: Humification is slowA lot of Leaching and PodsolisationIron and Aluminium pushed downConiferous ForestsNeedles don’t decompose easily little humificationProduce an acid humusNorthern LatitudesMoorlandsWest of IrelandReliefVegetationClimateSOIL FORMATIONDrainageParent MaterialSoil BiotaA Horizon often waterlogged because of impermeable iron pan that forms inbetween A and B horizon.Weathered Slowly producing a shallow soilFew Biota because cold climateTherefore, little humification
3 Brown Earths2010 Question 18Describe and explain the characteristics of any ONE soil type studied by you
4 Mature soils have 3 distinct horizons (layers) A Horizon – Contains topsoil, humus, vegetation not decayed, Organic ContentThe most fertile part of the soilSuffers the most leachingB Horizon - Contains subsoilContains leached mineral from A horizonC Horizon - The Regolith (recently formed soil)Sits ontop of bedrockContains large particles.
5 Brown Earths Where they are found 40-60 Degrees in Northern Hemisphere Cool Temperate ClimatesIreland-Russia in EastScotland-Portugal in SouthMost common soil in IrelandCrumb Texture mostlyKey wordsZonal SoilHumificationBurrowers and MixersLoamyPeds – space for waterBoulder Clay from Ice age depositsFreeze Thaw and Chemical weatheringHydrolysis
6 Brown Earths Crumb Structure Micro-organism activity – Bacteria Slightly acidic to slightly alkaline – it varies 5-7What impact do the following process have on Brown Earths ?Weathering – Mechanical/ChemicalErosionLeachingCalcificationHumificationSalinisation???
7 Brown Earth Soil (10,000 years) They form in warm climates, with mild winters and summers. South East IrelandFound in areas that have rainfall all year. 1,600-1,800 mm per yearFound in areas of deciduous forest – Oak/Ash – Ireland's natural vegetationWeathering is quite slow due to cool climate – What types of weathering?Some Humification because deciduous trees shed leaves every year.Mild climate assist decompositionLots of humus in these soils due to climate.Some Leaching – because precipitation exceeds evaporation.
8 What does it look like? Quite shallow Quite thick Humus Mild Acid HumusLight Brown A Horizon – becausecalcium, magneseare leached out by rainDark Brown B Horizon – because minerals have been washed down to here (Eluviation)Horizons often MergeThese are the main characteristics of the Brown Earth Soil.Explain why these soils have these characteristics eg. Quite shallow because of slow weathering. Which is due to the cool climate etc.
9 What does it look like?Quite shallow - weathering is slowQuite thick Humus – because there issome humificationMild Acid Humus – becausehumification is slowLight Brown A Horizon – becausecalcium, magneseare leached out by rainDark Brown B Horizon – becauseminerals have beenilluviated here.Horizons often Merge - biota mix the soil
11 Brown earth soils are widespread in Ireland, except in highland areas Brown earth soils are widespread in Ireland, except in highland areas. Soil organisms, like earthworms, mix the materials together, merging the boundaries between the horizons. These soils are leached, but not heavily, so the aluminium and iron oxides are dispersed through the soil to give the overall brown colour. The original vegetation was deciduous forest, resulting in a layer of decaying leaves giving a rich humus. The deep roots of these trees reached down to the 'B' horizon (unlike coniferous trees) tapping the nutrient supply and allowing good drainage.Climate -Precipitation greater than evaporation during summer months, resulting in only moderate leaching. Warm summersNatural vegetations and soil organisms - mixed broad leaf, much plant litter through this is more easily broken down by more active soil biota. A moderate or moder type of humus would develop from the plant litterRelief and drainage - downward movement of water, moderate leaching likelyParent material - strong influence on soil development
12 They generally have three horizons: the A, B and C horizon They generally have three horizons: the A, B and C horizon. Horizon A is usually a brownish colour, and over 20 cm in depth. It is composed of mull humus (well decomposed alkaline organic matter) and mineral matter. It is biologically active with many soil organisms and plant roots mixing the mull humus with mineral particles. As a result, the boundary between the A and B horizons can be ill defined in unploughed examples. Horizon B is mostly composed of mineral matter which has been weathered from the parent material, but it often contains inclusions of more organic material carried in by organisms, especially earthworms. It is lighter in colour than the A horizon, and is often weakly illuviated (leached). Due to limited leaching only the more soluble bases are moved down through the profile. Horizon C is made up of the parent material, which is generally permeable and non- or slightly acidic, for example clay loam.
14 Brown Earths - Characteristics ColourTextureStructureHumus ContentWater ContentPH Value
15 Brown Earths - Colour Brown due to soil formation processes Humification is main process – Dark BrownWhat is humification?What Plant Litter creates the humus?How does humus make its way down through the soil?No Distinct HorizonsBurrowers/Mixers – impact of climate
16 Brown Earths - Texture How fine or coarse the soil is Equal amts of Sand and Silt and Clay = LoamyLoamy means space for air and water to pass throughWell DrainedCrumby structure due to rich organic content of soil and living organismsMild temperatures – Cool Temperate OceanicThis helps – Burrowers and Mixers
17 Brown Earths – Humus Content Rich due to Deciduous VegetationProcess = HumificationModerate rainfall – eg mm in South East of IrelandRelief also affects the humus content – too high = less. The humus content in South East is affected by low-lying,undulating landMild Winters/Warm Summers – Decomposition is highest in these conditions
18 BROWN EARTHS – PH Value Refers to how acidic or alkaline the soil is Acidic soils = low ph valueAlkaline soils = high ph valueParent Rock generally influences the ph valueAcidic Brown Earths form on Sandstone and Alkaline Brown Earths form on LimestonePH Values of Brown Earths encourage the activity of earthworms and Bacteria