Soils of the Dry Regions PDF

Earth’s Soil [email protected] Alfred Hartemink Department of Soil Science Earth’s Soils Natural Science and Human Use 1 Earth’s Soil [email protected] 2 Earth’s Soil [email protected] 3 Earth’s Soil [email protected] 4 Earth’s Soil [email protected] Soil orders (Soil Taxonomy) Permanently froz...

Earth’s Soil [email protected] Alfred Hartemink Department of Soil Science Earth’s Soils Natural Science and Human Use 1 Earth’s Soil [email protected] 2 Earth’s Soil [email protected] 3 Earth’s Soil [email protected] 4 Earth’s Soil [email protected] Soil orders (Soil Taxonomy) Permanently frozen soil Gelisols Soils that consists of organic material Histosols Acid forest soils Spodosols Volcanic soils Andisols Highly weathered soils of the tropics Oxisols Clay soils with strong shrink/swell Vertisols Soils in dry areas Aridisols Strongly leached soils Ultisols Grassland soils Mollisols Moderately leached soils Alfisols Weakly developed soils Inceptisols Soils with little or no development Entisols 5 Earth’s Soil [email protected] Twelve Soil Orders Entisol (recent) Inceptisol (inceptum, Mollisol (mollis, soft) begining) Increasing soil depth, soil development Earth’s Soil [email protected] Entisol Inceptisol Mollisol 7 Earth’s Soil [email protected] Twelve Soil Orders Alfisol (pedalfer) Ultisol (ultimus, last) Oxisol (oxide) Maturation (loss of Silica) Earth’s Soil [email protected] Alfisol Ultisol Oxisol 9 Earth’s Soil [email protected] Twelve Soil Orders Aridisol (aridus, dry) Spodosol (spodos, wood ashes) Gelisol (gelare, very cold) Climate Specific Earth’s Soil [email protected] Aridisol Spodosol Gelisol 11 Earth’s Soil [email protected] Twelve Soil Orders Vertisol (verto, turn) Andisol (ando, dark soil) Histosol (histos, tissue) Parent material Specific Earth’s Soil [email protected] Vertisol Histosol Andisol 13 Earth’s Soil [email protected] Soil Taxonomy globally National system French system Soil Taxonomy WRB FAO Unesco 14 Earth’s Soil [email protected] Alfred Hartemink Department of Soil Science Soils of the Dry Regions Earth’s Soil [email protected] Dry regions § Not all dry regions are deserts (vegetation less) § Not all of them are hot, or sandy. § The antarctic continent is a dry, polar desert. § Dry region are prone to flash flooding when they receive rain. § The lack of soil moisture keeps minerals from leaching out, and can create cement like soil layers near the soil surface Earth’s Soil [email protected] Earth’s Soil [email protected] Soils are called Aridisols. In the Sahara and Australian outback, the soil are Entisols. Entisols are new soils, like sand dunes, which are too dry for any major soil horizon development. Earth’s Soil [email protected] 19 Earth’s Soil [email protected] Many organisms, including a living, biological crust, which is formed by algae, moss, and lichens in a group. When it rains, dormant seeds wake up and form desert blooms. Permanent vegetation (like cacti and shrubs) well adapted Deserts Earth’s Soil [email protected] 8% of the USA: Texas, New Mexico, Colorado, Wyoming, Montana, Arizona, Utah, Nevada, Idaho, California, Oregon, and Washington. 33% of the worlds land area 14% of with Antarctica Earth’s Soil [email protected] Soil characteristics Mineral soils About 33% of the earth Less rain that evapotranspiration May have salt within 1 meter depth 22 Earth’s Soil [email protected] Rainfall Rain and evapotranspiration Result: Accumulation of salts in the surface layers 0-400 mm per year Evaporation Transpiration From the soil From the surface vegetation Result: Little to no percolation No leaching Capillary rise Earth’s Soil [email protected] Soil chemical properties § High soil pH § Salinity (salt) Earth’s Soil [email protected] Desert pavement Also named: Surface pebble layers, stone pavement, gibber, gobi, sai, hammada, reg Causes: § Soil has washed and blown away § Upward migration § Windblown material § Weathering of surface rocks CaCO3 accumulation 25 Earth’s Soil [email protected] Desert varnish 26 Earth’s Soil [email protected] Horizons (layers) Sodium enriched clay horizon (through dispersion) Prismatic or columnar structure 27 Earth’s Soil [email protected] Aridisols globally Cool temperate deserts and warm deserts 28 Earth’s Soil [email protected] Salt crust 29 Earth’s Soil [email protected] Origin of the salt 1. From the parent material 2. Groundwater capillary 3. Blown in - Problematic for most plants, makes other nutrients less available 30 Earth’s Soil [email protected] Summary Low precipitation, high evaporation Processes involve salts, carbonates Buildup of salts Toxic trace elements – (for example selenium) Structure – sodium cause dispersion and loss of structure 31 Earth’s Soil [email protected] Desertification § The process by which fertile land becomes desert, as a result of drought, deforestation, or inappropriate agriculture. § Climatic change and human activities two main causes § Removal of the natural vegetation cover (fuelwood), agricultural activities, overgrazing Earth’s Soil [email protected] Vulnerable to desertification Earth’s Soil [email protected] Earth’s Soil [email protected] Use § The deserts are fertile § If provided with water, they can grow crops. § The Central Valley in California produces 250 types of fruits and vegetables, with river water, aquifers, and streams. Earth’s Soil [email protected] Irrigation § Irrigation water can be used up § flood irrigation can cause the water to evaporate very quickly. § Salts are left behind § Build up of salt is called salinization. § soils become too salty to grow anything. Earth’s Soil [email protected] Earth’s Soil [email protected] Earth’s Soil [email protected] Pasture and rangeland Earth’s Soil [email protected] Earth’s Soil [email protected] Earth’s Soil [email protected] Earth’s Soil [email protected] Earth’s Soil [email protected] Use of Aridisols § Irrigation required. § Land levelling required unless drip or pivot irrigation § With levelling subsoil may be exposed 44 Earth’s Soil [email protected] Use of Aridisols Salinisation (accumulation of soluble salts of Na, Mg, Ca) and alkalinization (Na) is a risk in irrigation Abundant plant nutrients (except N) Micronutrient deficient because of high pH Erosion is a problem 45