Soils: Formation, Properties, and Chemistry

1. SoilsChapters 15Living in the Environment, 15th Edition, Miller

2. Plow zone Elluviation – move minerals/organic matter Illuviation- accumulate materials due to rain Parent Material B Bedrock layer

3. Detritus is non-living particulate organic material It typically includes: the bodies or fragments of dead organisms, fecal material and colonized by communities of microorganisms which decompose (or remineralize) the material.

4. Soils: Formation Immature soil O horizon Leaf litter A horizon Topsoil B horizon Subsoil Bedrock C horizon Parent material Mature soil • Soil horizons • Soil profile • Humus Humus= nonliving, finely divided organic matter in soil, derived from microbial decomposition of plant and animal substances. Fig. 10.12, p. 220

5. Soil Properties Fig. 10.17, p. 224 Water Water High permeability Low permeability • Infiltration – ground water • enters soil. • Leaching - loss of water-soluble • plant nutrients from the soil • Porosity/permeability - amount of air space • or void space between soil particles. • Texture – describes particles in soil • Structure - arrangement of soil separates into units, solids and pore space. • pH - an indication of the acidity or alkalinity of soil and is measured in pH units. • Soil pH is defined as the negative logarithm of the hydrogen ion concentration. • The pH scale goes from 0 to 14 with pH 7 as the neutral point.

6. Ternary diagram

7. Soil Quality Texture Nutrient Infiltration Water-Holding Aeration Tilth Capacity Capacity Clay Good Poor Good Poor Poor Silt Medium Medium Medium Medium Medium Sand Poor Good Poor Good Good Loam Medium Medium Medium Medium Medium Loam = soil composed mostly of sand and silt, and a smaller amount of clay (about 40%-40%-20% concentration respectively). Tilth = suitability of soil for planting crops; tilling land is to mechanical manipulation to improve crop growth. Fig. 10.15b, p. 223

8. Soil Chemistry • Acidity / Alkalinity – pH • Major Nutrients • (N) Nitrogen– green leaves, quality & protein of fruit • (P) Phosphorus (phosphates) – strong roots, increases seed yield and fruit development • (K) Potassium(potash) – color of flowers, quality of fruit, vigorous root growth • http://www.ncagr.gov/cyber/kidswrld/plant/nutrient.htm

9. N-P-K (Nitrogen- Phosphorus- Potassium) are the 3 most abundant ingredients listed on EVERY fertilizer label. You will see them on the label as three numbers. Such as: 30-10-10 / 10-5-5 / 21-0-0 The first example, 30-10-10: In 100 pounds of that fertilizer, there would be 30 pounds of available nitrogen, 10 pounds of available phosphorus and 10 pounds of available potassium (potash). The remaining 50 pounds are inert or inactive ingredients.

10. N = green leaves/ • fruit • K = fruit quality/ • flower color/ • vigorous roots • P = roots/ • seed yield/ • fruit development

11. To turn a lawn green and get it growing, 21-0-0 is the fastest and cheapest way to go (NPK, N = green leaves). That is Sulphate of Ammonia. However, to promote a healthy lawn that is more drought-tolerant, you would want the roots (P = roots, K = vigorous roots) to be well developed also. A general purpose lawn fertilizer such as 10-6-4 (NPK) would be a far better diet to achieve a truly healthy lawn.

12. Acidity / Alkalinity – pH • Proper pH directly affects the availability of plant food nutrients • Eastern Pa soil pH 4-6 • Agricultural soil is best if between pH 6 – 8 (except for certain acid loving plants) • ‘Sour’ if too acidic • ‘Sweet’ if too basic Acid rain pH 4.0

13. Acidity / Alkalinity – pH • Too acidic or basic will not • Allow compounds to dissolve • Allow presence of certain ions • If soil is too acidic, add ground limestone • If soil is too basic, add organic material like steer manure • Soil in Appalachian Mountain valley is near limestone deposits • Normally acidic soil is made more basic by lime = good growing soil, pH 6-8.

14. Nitrogen Content • Importance • Stimulates above ground growth • Produces rich green color • Influences quality and protein content of fruit • A plant’s use of other elements is stimulated by presence of N • Taken up by plant as: • NH4+ (ammonium ion) and • NO3- (nitrate) • Replenished naturally by rhizobacteria on legume roots (rhizomes – thick plant stem, with roots, growing underground) • Fertilizer from manure or chemical rxn.

15. Phosphorus for Growth • Abundant in • Strong root system • Increases seed yield and fruit development • Parts of root involved in water uptake • Major role in transfer of energy • Taken up by plant as H2PO4- (dihydrogen phosphate) and HPO4-2 (hydrogen phosphate) • Fertilizer is made from rock phosphate

16. Potassium Content • Potash • Important in vigor and vitality of plant • Carries carbohydrates through the plant • Improves color of flowers • Improves quality of fruit • Promotes vigorous root systems • Offsets too much N • Found naturally in feldspar and micas

17. Justus von Liebig’s Law of Minimum Plant production can be no greater than that level allowed by the growth factor present in the lowest amount relative to the optimum amount for that factor

18. Soil Formation Soils develop in response to: • Climate • Living organisms • Parent Material • Topography • Time

19. Climate • Two most important factors that determine climate are: Temperature and Moisture and they affect: • Weathering processes • Microenvironmental conditions for soil organisms • Plant growth • Decomposition rates • Soil pH • Chemical reactions in the soil

20. Parent Material • Refers to the rock and minerals from which the soil derives. • The nature of the parent rock (bottom layer) has a direct effect on the soil texture, chemistry and cycling pathways. • Parent material may be native or transported to area by wind , water or glacier.

21. Topography • Physical characteristics of location where soil is formed. • Drainage • Slope direction • Elevation • Wind exposure • Viewed on Macro-scale (valley) • or Microscale (soil type in field)

22. Time • After enough time, the soil may reach maturity. • Depends on previous factors • Feedback of biotic and abiotic factors may preserve or erode mature profile.

23. Physical includes temperature changes (freezing and thawing, thermal expansion), crystal growth, pressure, plant roots, burrowing animals causes disintegration of parent material and facilitates chemical weathering Chemical always in water includes hydration, hydrolysis, oxidation, reduction, carbonation and exchange examples : oxidation of Fe to form limonite, deposited in joints, inhibits groundwater flow hydrolysis of feldspars to form clay (kaolin) - forms infill for joints Destructional -WeatheringLandscapes broken down by chemical & physical processes & erosion

25. Destructional - Mass wasting • Gravitational movement of weathered rock down slope without aid of water or wind (landslips) • transported material is called: colluvium • often set off by man’s activity • can involve very small to immense volumes of material • sliding, toppling, unravelling, slumping • controlled by discontinuities (joints, bedding, schistocity, faults etc)

27. Destructional - Erosionmost significantly by running water • Sheet erosion • by water flowing down valley sides • severe when vegetation removed and geological materials uncemented • Stream erosion • materials brought downslope by mass wasting and sheet erosion are transported by streams • erosion by the streams - meanders etc

29. Destructional - Karsts • Forms by dissolution of limestone - limestone is only common rock soluble in water - dissolved carbon dioxide in rain water • form highly variable ground conditions • formation of sink holes - when buried leads to surface subsidence