Soil The nation that destroys its soil destroys

Soil “The nation that destroys its soil destroys itself. ” -Franklin D. Roosevelt

State Soil- Orovada soils are extensive in northern Nevada, where they have an extent of more than 360, 000 acres. They are common soils on semiarid rangeland with sagebrush-grass plant communities. Orovada soils are arable when irrigated and are considered prime farmland. Alfalfa for hay and seed, winter wheat and barley, and grass for hay and pasture are the principal crops grown on these soils. Orovada soils are well drained and formed in alluvium derived from mixed rock sources and in loess and volcanic ash. These soils typically occur in the Great Basin section of the Basin and Range physiographic province. The mean annual precipitation is about 8 inches, and the mean annual temperature is about 47 degrees F.

Why study soil? n n Soil stores & purifies water Waste products & chemical pesticides are destroyed by soil microorganisms (Percolation) Sediment in water and dust in air contributes to pollution of our environment Production of our food depends on it

Formation of Soil n 1. Living matter ¡ n 2. Climate ¡ n n Based on temperature & precipitation 3. Parent materials 4. Relief ¡ n Animals, plants, microorganisms Slope and landform 5. Time

It takes 1 year to make 1 mm of topsoil

Processes most responsible for soil formation n Weathering ¡ ¡ n Erosion ¡ ¡ n n Breaking down of rock Physical, Chemical & Biological n **Know examples (Ch 9 textbook) Movement of rock/dirt Wind or water Deposition Decomposition (adds nutrients)

Layers of soil= HORIZONS n Soil profile Mineral horizon Heavily leached area Zone of illuviation for leached material from A & E horizons. Rich in clay, Al or Fe

Acronym for Soil Layers n O(organic material)- Only A(top soil)- Americans E(zone of leaching)- Eat B(Subsoil) - Bacon C(Regolith)- Covered R(Bedrock)- Raisins

*Not to be confused w/hummus Humus n n Dark-colored organic material that remains after decomposition of leaf litter, drippings, & plant/animal remains Plant roots & decomposers are found in O & A horizons ¡ n O= leaf litter; A= nutrients Benefits: ¡ ¡ ¡ Nutrient benefits Water holding capacity Aeration capacity Promoting root growth Increasing porosity of soil

Leaching n Leaching: When minerals or ions dissolved in water percolate downward, making them unavailable for plant use ¡ The degree of weathering & amount of organic matter decreases as we go down the soil profile

Soils have a limited nutrient reservoir & must be replenished periodically

WHICH BIOMES ARE USUALLY CONVERTED INTO ARABLE LAND?

Grasslands & Forests Rich in Organic Matter

Tropical Rainforest Soil: Nutrient rich?

CHEMICAL PROPERTIES OF SOIL

What plants need… Macronutrients Micronutrients N n P* n. K n n Ca, Mg, S C, H, O ¡ *frequently limiting factor n n n Fe Mn B Cu Zn Cl Molybdenum

How can nutrients be added to soil? ¡ ¡ Crop rotation (legumes→ provide ammonia naturally) Organic fertilizers: manure, bone meal, crop residue, compost Inorganic fertilizers: store bought bags Sewage sludge

EUTROPHICATION n n Run-off from fertilizers or animal waste… Excess N & P can lead to EUTROPHICATION ¡ causes algal bloom → blocks sunlight for other producers algae die decomposer (bacteria) population increases→ decreases oxygen in water→ larger organisms like fish die

p. H (<7=acidic >7=alkaline) n Ideal p. H: 6 -7 ¡ n Too acidic? ¡ n Fe, B, & Mn less available To make soil more acidic… ¡ n Aluminum (Al) toxic Too basic? ¡ n Why? Nutrients more soluble Add powdered Sulfur or Aluminum sulfate To make soil more basic (alkaline)… ¡ Add lime

p. H Neutral & Alkaline soils are common Acidic soils are common

Cation exchange & p. H Soil particles that are negatively charged hold cations (like Ca+2, Mg+2, K+) HOW IT WORKS: In cation exchange, plant roots donate H+ to the soil in exchange for these nutrients, which the soil particles then replenish by exchange with soil water. Cation exchange capacity expresses a soil’s ability to hold cations (preventing the soil from leaching & thus making them available to plants) & is a useful measure of soil fertility As soil p. H becomes lower, cation exchange capacity diminishes, nutrients leach away & soil instead may supply plants w/harmful Al ions.

PHYSICAL PROPERTIES OF SOIL

SOIL IS THE #1 WATER POLLUTANT Blocks out light, reducing photosynthesis this reduces oxygen levels

PHYSICAL PROPERTIES OF SOIL COLOR POROSITY & PERMEABILITY Color can be indicative Porosity: Amount of space between of soil’s nutrients particles Dark brown/black: lots of humus (organic matter) White/light gray: leaching or low organic matter Red: lots of iron Permeability: Rate at which water & air move through rock/sediment More porous → More permeable if pore spaces are connected

Soil Texture Sand 0. 05 -2 mm Silt 0. 00020. 05 mm <0. 0002 mm Clay Loam High permeability because of high porosity Low permeability Equal Ideal soil for portions of all agriculture three texture types

n Size of soil particles determines movement of groundwater

n Clay percentages are read from left to right across the triangle n Silt is read from the upper right to lower left n Sand from lower right towards the upper left portion of the triangle n The intersection of the three sizes on the triangle gives the texture class. n For instance, if you have a soil with 20% clay, 60% silt, and 20% sand it falls in the "silt loam" class.

Soil Structure A measure of the “clumpiness” of soil If soil is too compacted (large clumps) plant roots have a hard time getting air and water Farmers can create this if they till the land too often Also caused by grazing livestock

IRRIGATION= WATER USED FOR AGRICULTURE

Effects of Excessive Irrigation

WATERLOGGING n When soil is saturated with water ¡ Occurs when water accumulates underground & gradually raises the water table, due to farmers applying large amounts of irrigation water n n Plant roots die due to lack of oxygen required for cellular respiration Decomposing organisms in soil also die due to lack of oxygen.

SALINIZATION n Salinization ¡ Repeated applications of irrigation water in dry climates leads to the gradual accumulation of salts in upper soil layers n ¡ n n Stunts plant growth, reduces crop yields & can eventually kill plants & ruin land Decreasing salinization 1. Use mechanism that does not allow much evaporation ¡ n Salt collects in topsoil when water evaporates Drip irrigation or underground pipes 2. Plant salt resistant crops, like Barley

Salinization n Most severe salinization: ¡ China, India, Egypt, Pakistan, Mexico, Australia, & Iraq ¡ In the U. S. ¼ of our cropland is affected by salinization, especially in the western states

BIGGEST PROBLEM RELATED TO OVER IRRIGATING… Depletion of groundwater and surface water

Desertification n Loss of more than 10% productivity due to. . . ¡ ¡ ¡ ¡ n Erosion Soil compaction Forest removal Overgrazing Drought Salinization Climate change Expanding deserts & creating new deserts from once-fertile land

Overgrazing n n If grazing animals move from region to region without lingering in any one place too long, the vegetation can usually regenerate Overgrazing causes: ¡ ¡ ¡ Soil erosion (no vegetation to hold soil in place) Invasive species to invade Compacts soil, making it harder for water to infiltrate (plant roots are affected)

Forestry n When a tree/vegetation is removed, erosion by wind or water increases because the roots not are there to secure the soil ¡ ¡ Clear cutting can lead to severe erosion, particularly on steep slopes Alternative programs that remove fewer trees over longer periods of time can minimize erosion

Chemical Contamination Salinization Desertification