Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings World soil conditions Soils are becoming degraded in many regions.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Soil Definitions 1)The unconsolidated organic and mineral material on the earth’s surface that is capable of supporting plants. (MA Envirothon Team Resource Manual) 2)A dynamic natural body, in which plants grow, that is composed of mineral and organic materials and living organisms. (Brady & Weil, 11 th Ed.)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Soil as a system Soil is a complex mixture of organic and inorganic components.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Components of Soil Mineral materials = boulder, stone, cobble, gravel, sand, silt, and/or clay sized particles of gneiss, granite, schist, or slate. Organic materials = leaf litter, crop residue, decomposing animal bodies, and compost. Living organisms = plant roots, earthworms, nematodes, fungus, bacteria colonies

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glacial Till Unsorted/stratified material deposited beneath and within glacial ice. Heterogeneous mixture of all particle sizes (boulder to clay). Oldest surficial deposit overlying most bedrock areas. Paxton series Mass. State soil

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Five soil forming factors 1)Parent material : Rocks 2)Climate : Precipitation, Temperature changes 3)Organisms : Bacterial and fungal colonies, worms, rodents 4)Topography : Slope, Landscape position 5)Time : How long climate has been altering parent material geologic time

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Parent material In the Appalachian Mts., granite, gneiss, schist, and slate represent the geology of the parent material. Organic soil material forms from decaying carbon life forms. Coastal areas are underlain with ocean sedimentary material. Each of these materials produce distinctive groups of particles from the weathering process. Climatic & glacial forces break particles from the rock surfaces, forming boulders, stones, cobbles, and gravel, which are called fragments. sand, silt, and clay.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Three kinds of weathering Physical or mechanical Chemical Biological

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Parent material (continued) Parent material can be rocks weathered in place (residuum) Or mineral material deposited by water (alluvium) wind (eolian) gravity (colluvium) lake bed sedimentation (lacustrine) ocean deposits (marine sediment) glacial deposits (till) Or organic material

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glacial processes have determined the parent material in much of New England. In areas where till deposits are thin bedrock is seen at the surface and within the soil profile. Parent material above bedrock is still glacial till.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Soil fungi

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Earthworm Burrows middens Middens: piles of residue around the mouth of earthworm burrows.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Topography Topography affects the water flow on and through the soil, which affects the soil formation processes.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Time Over time, the affects of climate, topography, and organisms continually alter the parent material and soil particles, which results in the formation of recognizable soil profiles. It takes 500 years to form one inch of topsoil. It takes thousands of years to form a weakly structured subsurface horizon like we have in New England. It takes tens of thousands of years to form the well structured clay subsurface horizons of the south and mid-west.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings An E horizon can develop in this area. Bedrock can lie below the C horizon. In this position, the bedrock is called an R horizon.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Soil profile O Horizon: Organic or litter layer A Horizon: Topsoil; mostly inorganic minerals with some organic material and humus mixed in; crucial for plant growth E Horizon: Eluviation horizon; loss of minerals by leaching, a process whereby solid materials are dissolved and transported away B Horizon: Subsoil; zone of accumulation or deposition of leached minerals and organic acids from above C Horizon: Slightly altered parent material R Horizon: Bedrock

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Soil profile Consists of layers called horizons Simplest: A = topsoil B = subsoil C = parent material But most have O, A, E, B, C, and R

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Soil characterization Soil can be characterized by color and several other traits: Texture Structure pH

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings So what? Physical differences The size of sand and clay give a horizon different physical & chemical properties. Sand particles are much larger than clay particles and, sand is blocky shaped while clay is platy. A collection of sand particles create air spaces that are larger and more connected than those created by a collection of clay particles. Chemical differences Sand particles have no charge on their surface. Clay particles have negative charge on their surface and adsorb elemental nutrients such as Ca, Mg, Fe, NO 3, PO 4.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Soil Structure Definition: Soil structure is the natural organization of soil particles into units called peds. When structure is examined, its type, grade, & size is determined, and recorded in that order. Most structure types in New England are granular, subangular blocky, massive, or single grain because clay contents are usually less than 40%.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Soil texture Determined by size of particles Three main categories: Clay = particles < mm diameter Silt = particles 0.002–0.05 mm diameter Sand = particles 0.05–2.0 mm diameter Best for plant growth is loam, an even mix of these three types.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Granular crumb size units; often associated with A horizons that contain organic material Sub-angular blocky rounded edges and faces; often associated with B horizons Massive No structural units; material is a coherent mass Single grain No structural units; loose sand

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Soil texture

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Soil structure Soil structure: a measure of the “clumpiness” of the soil Soil pH: the degree of acidity or alkalinity, which influences a soil’s ability to support plant growth