Environmental science Soil Environmental science

Pre Test What is the difference between Soil Profile and Soil Horizons? 01 Which horizon accumulates organics and clays by the movement of water. 02 What are 5 soil forming factors 03 What horizons are considered Master horizons 04

Soil is made of What? 45% Mineral – Clay, Sand, Silt 25% Air – Oxygen is vital for plant growth and certain microorganisms 25% Water – Depends on porosity and precipitation 5% Organic Matter 5% Organisms (burrowing animals, bacteria, fungi, protists) 10% Roots 85% Humus Soil is made of What? NRCS Soils

Soil Texture University of Illinois Soil Science Extension Particle Size effects porosity of soil Influences water holding capacity Water availability for plants Water film around particles cannot be accessed by plants University of Illinois Soil Science Extension

Fun Fact Soils actually have a negative charge specifically clays and organic matter 1 Nutrients needed by plants are positively charged. 2 This is what we call cation-exchange or on soil samples cation-exchange capacities (CEC) 3 University of Illinois Soil Science Extension 4

Sand Silt Clay Soil Texture Lacks the capacity to hold water and nutrients Sand Increases water holding capacity Silt Smallest particle Greatest water and nutrient retention Clay U of I Rangelands p. 31

Soil Structure Arrangement of soil particles Blocky Platy Granular Prismatic Columnar Massive

Soil Structure Greatly effects the permeability of soil (water or air) Permeable Least Permeable

Soil-Forming Processes Additions – addition of organic or mineral Organic matter Wind blown matter Rainfall adds Nitrogen and other soil particulates Losses – Loss of organic or mineral Deep Leaching Surface loss Translocations – movement within soil Low rainfall areas causes saline/alkaline problems because of incomplete leaching Transformations – mineral or organic modification Organic matter to humus by microorganisms Chemical weathering of parent material (Fe -->Fe203) file:///Users/Katy2/Downloads/surdown.pdf

Soil Forming Factors Weathering of minerals i.e. parent material Climate Biota (living plants/animals and the decomposition of organic matter) Typography Time Soil and Our Environment p. 19-25, Text p. 292

Weathering Breakdown of parent material in soil formation by physical and chemical breakdown Mechanical Weathering Freezing and Thawing (ice expansion) Uneven Heating Abrasion – ice, water and wind Shrinking Swelling Root activity (Cornell University) Chemical Weathering Oxidation Hydrolysis Acidic rain

Climate Dry, cold climates Warm wet climates Slower Soil Formation Slower weathering (depending on parent material) Slower decomposition Warm wet climates Faster weathering (depending on parent material) Faster decomposition Text, p. 292 Slower Soil Formation Faster Soil Formation

Biota Interaction of soil organisms such as plants, animals, microbes Burrowing animals (gophers, earthworms, ants, etc.) help mix nutrients Plant Roots some can reinstate soil nutrients Breakdown parent material Microorganisms (bacteria, fungi, protists) Decompose organic matter Text p 292, Soils and Our Environment p. 20

Typography The lay of the land (climate has an effect) Steep hillsides Developing soil profiles Nutrients are unable to be leached to lower horizons Aspect – SW slopes receive more sun causing dry/arid Rolling Hills Deep soil profiles because water leaches materials to lower horizons Good A,O Horizons Valleys or Depressions Rich organic soils Salt marshes Soils in Our Environment p. 22, Text 297

Time It takes a minimum of 1 year to develop 1” of top soil Depends on Climate, Parent Material, Organisms, Topography Effects the amount of time the soil is formed. NRCS Soil Formation