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Soil Resources

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Published in: Geography
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Soil resources and food production systems

Pradeep K / Bangalore

10 years of teaching experience

Qualification: Ph.D (Kuvempu University, Shimoga - 2008), B.Ed (Mysore University, Mysore - 2010), M.Sc (Bangalore University - 1997), B.Sc (Bangalore Medical College and research Institute - 1994)

Teaches: Bio Technology, Biology, EVS, Zoology, B.Sc Tuition, Botany

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  1. Unit 3: Human population, carrying capacity and resource use 3.4 The Soil System D
  2. The Soil System o Soils are major components of the world's ecosystems. OThey form at the interface of the Earth's atmosphere, lithosphere (rocks), biosphere(living matter) and hydrosphere (water). OSoils form the outermost layer of the Earth's surface, and comprise weathered bedrock(regolith), organic matter (both dead and alive), air and water.
  3. Interactions of Soil O The Soil interact with the atmosphere, lithosphere, biosphere and hydrosphere. The water cycle moves through the soil by infiltration and water may evaporate from the surface D The atmosphere may contain particulate matter that is deposited on the soils and particles may blow up into the atmosphere D Rocks in the lithosphere weather to form soils, and soils at depth and pressure may form rocks D Plants in the biosphere may extract nutrients from the soils and dead plants may end up forming parts of the soil
  4. Contrasts - Different Soils Nutrient storage capacity Air Space Primary Production Water retention and availability Clay Sticky and easily waterlogged High Sand Fast draining soils that dry outs easil low loam High to Medium Medium low Medium/low High low Medium Medium
  5. Importance of Soil o Soil : naturally occurring unconsolidated material on the surface of the earth that has been influenced by parent material from the rock below, climate, macro-organisms and micro-organisms. D Soils are complex systems which carry out a wide range of functions that are critical to the functioning of the Earth as a whole as a system
  6. Importance of Soil D Typical cultivated soil: 50-60% mineral particles, 1-5% organic matter, & 40% pore spaces between the particles which will have varying amounts of air and water in them. D Zonal classification of soil : Climate factors D HUMUS: A dark crumbly substance that is very fertile for plant growth. D Precipitation effectiveness (Rainfall): is the balance between precipitation and potential evapotranspiration. Influences direction of water movement in soil, if precipitation is > Leaching
  7. Soil Profile o scil suface eluvial zone illuvial zone T-Tndecampasd crgaric detris, clecctnpasetl •zga.ric mat.erial, and A 1 eached miner al horizon With a high Frapctt.ian of argaric maiter (dark in cal•z) A colcred layer representing the zcrœ of ma.xitmxn leaching zone of acclxnulaü•m of weathzmgproducts such as S.licate Clay, i.rm, allÀtLimun, hxnus, carbonates, wpsuttL, dlica Relaüvely Imalterecl m ateria.l Hard be&ack
  8. Soil Profile Most soils have three major horizons - the surface horizon (A) the subsoil (B), and the substratum (C) Some soils have an organic horizon (O) on the surface, but this horizon can also b The master horizon, E, is used for horizon have a significant loss of minerals (eluviat Hard bedrock, which is not soil, uses the If
  9. Soil Horizons o Vertical succession down through a soil ovarious layers in HORIZON's D O: Leaf litter, humus, vital in soil fertility. DA : Mixed organic layer , plant roots, decomposed organic material : Humus DE: Eluvial or leached horizon (sand, silt with lost mineral and clay) DB: Deposition or Illuvial horizon (iron, humus & Clay) DC: Transition zone - broken rock bed DR: Parent bed rock (hard)
  10. Process of soil formation O Three Process involved D Inputs OTransformation DOutput
  11. Inputs into a soil O Organic material from decaying flora and fauna DPrecipitation, gases and solid particles from the atmosphere OGases from the respiration of soil fauna OExcretion from plant roots OMinerals from the breakdown of parent material
  12. Outputs from the soil O Nutrient taken up by plants growing in the soil. D Nutrient losses through leaching D Losses of soil through soil erosion and mass movement (e.g. soil creep) O Evaporation
  13. Soil Texture O Refers to size of solid particles in a soil O Mineral composition is made up of 3 components: CLAY, SILT & SAND O Relative proportion of each component gives the soil texture. o Ref: as SOIL SEPARATES - types of soil have specific range of soil particle size. OSand particles are sub divided into FIVE from very fine to coarse.
  14. Name of soil separates CLAY SILT Very fine Sand Fine sand Medium Sand Coarse Sand Very Coarse Sand Soil Separates 0.05-0.10 0.10-0 25 0.25-0.50 0.50-1 oo 1.00-2 oo Size (diameter/mm) USDA < 0.002 0.002-0.05
  15. Soil Textural Triangle - Clay, Silt & Sand percent 40 IV and percent 70 Cla loam Sandy clay loam Medium loam Loamy loa o sand 100 90 percent SAND clay loam Silty loam
  16. Soil texture o Affects: D Moisture content and aeration ORetention of nutrients OEase of cultivation O root penetration of crops and other vegetation
  17. Sandy Soils D Poor structure, gritty in nature and lack in cohesion D Feel dry compared to loam and clay soils D Free draining, dry out rapidly DLack nutrients - washed out by downward movement of water D Advantage: a. Easy to cultivate - light in nature D b. Warm up quickly in spring - helps to provide a longer growing season. DManagement of the sandy soils - often ignored in agriculture.
  18. Loam Soils o Has greater cohesion than sandy, hold together better when a handful is picked up. Soft and rich in touch o Comprised of 40%-40%-20% of sand, silt and clay o It is considered to be the perfect soil. The texture is gritty and retains water very easily, yet the drainage is well. There are various kinds of loamy soil ranging from fertile to very muddy and thick sod. D Contains more humus & nutrients than others, better infiltration and drainage o Loams may be wet in winter as water table raises but are well drained in summer
  19. Clay Soils D Heaviest of the three soils, fine particles resulting in few air spaces - give the soil a very high level of cohesion. D Clay drains poorly and feels lumpy and sticky when it is very wet DOften sticks to footwear and tools in gardens OFeels smooth not gritty, heavy to cultivate - forms clods that are difficult to separate D Consist of 50% of clay particles, attract positively charged particles - calcium, potassium & magnesium OSIow draining can lead to water logging
  20. Summary & comparison : Types of Soils Characteristics Sandy Soil Mineral Content High Drainage Water holding capacity Air spaces Biota & Potential to hold organic matter Primary productivity Very Good Low Large Low Low Loam Soil High Good Intermediate Intermediate High High Clay Soil Intermediate Poor High Small Intermediate Intermediate
  21. Soil Degradation D Is a global process, involves both the physical loss (erosion) and the reduction in quality of topsoil associated with nutrient decline and contamination Olmpacts significantly on agriculture, urban environment, pollution and flooding DLoss of upper soil horizon containing organic matter and nutrients D Thinning of soil profiles reduces crop yields on degraded soils. OThe GLOBAL ASSESSMENT OF HUMAN-INDUCED SOIL DEGRADATION (GLASOD) undertakes global soil survey
  22. Process of Soil degradation D Main cause - soil removal of the natural vegetation cover, leaving the surface exposed to the elements DDeforestation and Overgrazing - main problems DResult of loss of vegetation - lead to wing and water erosion DAgricultural mismanagements - lack of knowledge, short term gains D Shifting cultivation without fallow periods DAbsence of soil conservation measures DCultivation of fragile or marginal lands, unbalanced fertilizers use and the use of poor irrigation techniques
  23. Major causes of soil degradation bi,qnS MAJOR TYPES UNDERLYING CAUSES rut
  24. Soil degradation as a result of: O Erosion by wind and water (80%) OPhysical degradation (loss of structure, surface sealing and compaction) OChemical degradation (changes in pH, acidification, and salinisation) OBiological degradation (loss of organic matter and biodiversity) OCIimate and land use changes (may accelerate the above factors)
  25. Biological Degradation D Heavy and sustained use of artificial fertilizers D Loss of organic matter - reduces the soil aggregates which under the influence of rainfall may then break up - Results in SOIL CRUST'S - reduced infiltration of water in to the soil D Increases the likelihood of run off and water erosion happening. DLoss of structure - compaction from agricultural machinery and cultivation in wet weather.
  26. Chemical Degradation D Loss of nutrients or inorganic matter, salinisation, acidification, soil pollution and fertility decline. D Acid rain, Combustion of fossil fuels - acidity D Salinisation - arid areas, coastal zones DSOIL TOXICITY - municipal and industrial wastes, oil spills, excessive use of fertilizer, herbicides and insecticides, or release of radioactive materials, acidification by airborne pollutants
  27. Consequences of Soil Degradation O Desertification OSalinisation OAcidification ODust storms O Severe drought
  28. Soil Degradation - threat to food security? O Reduced food supply O Reduced farming income O Higher food prices O Increased malnutrition O Rural to urban migration
  29. Soil conservation measures D Soil Conditioners - materials added to soil to improve soil fertility. D Wind reduction techniques - Shelterbelts, hedgerows, Strip cultivation D Cultivation Techniques: Contour ploughing, Terracing DConverting land from arable to pastoral uses. DCrop rotation - include grasses D Leaving unploughed grass strips between ploughed fields D Selecting and use of machinery, alter harvesting
  30. Soil conservation measures soil protection for cropland juduced tillage stubble-tnutching strip-cropping reduced cotnp actio n stubtJJc-gnuJch sed shelter- belts gin g and dtvinq out optimal s trip-croppmg contour ploughing terracing up.hBt plant&ig
  31. Soil conservation measures soil protection for grassland topdressing shelter betts riparian fencing spaced tree planting I grassed O O dcbris watcrv,tos O O close inter- locked troc plantülg 00000 retirement fencing
  32. Comparisons of No-till, Conservation Tillage & Conventional Tillage CONVENT'*AL REOUCEO NO
  33. Comparison of Conservation tillage & eahhworms Conventional Conventional Tillage Soil -tillage Mix oil nutrient leachin Conservation Tillage Soil soil nutrient retent on - arthropods - nematodes - protozoa - fungi
  34. Factors Soil Degradetion Procossos Soil orosion Nutrient runoff Waterlogging Desertification Acidification Compaction Crusting Organic matter loss Selinization Nutrient depletion by leaching Toxicant accumulation - Soil Productivity Soil productivity Soil Conservation Practices Conservation tillage Crop rotations Improved drainage Residue managoment Water conservation Terracing Contour farming Chemical fertilizers Organic fertilizers Improved nutrient cycling Improved systems to match soil, climate and cultivars
  35. Factors Strategy Alternative Agriculture Skilled managomcnt Crop rotationg Organic recycling Reduced chemical input Croplivestock systems Integrated pest management - Soil Quality Linkage Goal Soil Quality Sustainable Agriculture Productive/profitable Energy conserving Environmentally sound Economically viabic Consotvos natural regources Improves health/ food quaiityJsafety

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