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SOIL FERTILITY
<ul><li>Ability of soil to supply nutrients for plant growth   </li></ul>
    <ul><li>Soil is storehouse of nutrients   Some available, some not </li></ul>
  Soil fertility:    <ul><li>quantity of nutrients soil contains </li></ul><ul><li>how well protected from leaching </li><...
  Plant nutrients    <ul><li>Essential  elements  needed for plant growth </li></ul>
Plant nutrients <ul><li>Plants absorb 90 elements </li></ul><ul><li>Only a few needed for growth </li></ul><ul><li>Some no...
 
<ul><li>How to determine which are essential? </li></ul>
Essential plant elements <ul><li>1. lack of element stops plant from growth or reproduction </li></ul><ul><li>2. element i...
  17 essential elements   <ul><li>3  account for 95% plant needs </li></ul><ul><li>carbon, oxygen and hydrogen </li></ul><...
Non-minerals          Macronutrients Air and Water Carbon (C)        Hydrogen (H)       Oxygen (O)
  14 come from soil    <ul><li>6  used in large amounts: </li></ul><ul><li>macronutrients </li></ul><ul><li>Nitrogen Calci...
  Primary Macronutrients   <ul><li>Nitrogen   Phosphorus Potassium </li></ul><ul><li>Not always available in large enough ...
Secondary Macronutrients   <ul><li>Calcium   Magnesium  Sulfur </li></ul><ul><li>Soil usually has plenty </li></ul>
   Micronutrients  <ul><li>8 nutrients left  </li></ul><ul><li>Used in small amounts </li></ul><ul><li>Plant won't grow no...
  NUTRIENT IONS <ul><li>Plants absorb some of the nutrients as  ions  instead of elements </li></ul><ul><li>Ion has positi...
<ul><li>Ion has: </li></ul><ul><ul><li>positive charge  cation </li></ul></ul><ul><ul><li>negative charge anion </li></ul>...
  <ul><li>Ions form in soil when compounds dissolve in water     Example: </li></ul><ul><li>Potassium nitrate (fertilizer)...
  <ul><li>Plant roots  absorb  ions - soak like a sponge </li></ul><ul><li>Soil particles  adsorb  ions - hold on to them ...
 
SOURCES OF ELEMENTS IN SOIL   <ul><li>Nutrient elements present in soil in four places (pools) </li></ul>
SOURCES OF ELEMENTS IN SOIL <ul><li>1. soil minerals  </li></ul><ul><li>major source </li></ul><ul><li>released slowly by ...
SOURCES OF ELEMENTS IN SOIL <ul><li>2. organic matter </li></ul><ul><li>large amounts of nitrogen </li></ul><ul><li>nutrie...
SOURCES OF ELEMENTS IN SOIL <ul><li>3. adsorbed nutrients </li></ul><ul><li>held by clay and humus particles </li></ul><ul...
SOURCES OF ELEMENTS IN SOIL <ul><li>4. dissolved ions </li></ul><ul><li>ions in soil solution </li></ul><ul><li>plants abs...
 
  Soil colloids     <ul><li>Tiny particles of clay and humus with slight electrical charge  </li></ul><ul><li>This charge ...
    CATION EXCHANGE     <ul><li>Negative charge on soil colloids: </li></ul><ul><ul><li>attracts positively charge ions </...
  adsorption    <ul><li>Negatively charged colloid attracts swarm of cations from soil solution </li></ul>
 
 
Cation Exchange <ul><li>When one ion taken up by plant (pulled off soil particle), replaced by another. </li></ul><ul><li>...
  <ul><li>Ability of soil to hold nutrients –  </li></ul><ul><li>directly related to the number of cations it can attract ...
<ul><li>Displacement of cations depends on: </li></ul><ul><li>Relative concentration </li></ul><ul><li>high concentration ...
high CHARGE displaces low Al>Ca>Mg>K>Na
 
<ul><li>Plant roots have negatively charged surfaces  </li></ul><ul><li>positively charged hydrogen ions attached </li></u...
   Cation Exchange Capacity  (CEC)  <ul><li>The ability of soil to hold exchangable ions </li></ul><ul><li>CEC expressed i...
 
Bonding strength    <ul><li>If two cations are present in soil in equal numbers </li></ul><ul><li>one that bonds most stro...
Mass action  <ul><li>more ions in soil,  </li></ul><ul><li>more exchange sites it will occupy </li></ul>
  <ul><li>Weakly held cations are more available for plant uptake </li></ul>
<ul><li>A clay particle is covered with negative charges  </li></ul><ul><li>Opposites attract, ions with positive charge(s...
  <ul><li>Several nutrients available to plants as negatively charged ions –  anion exchange </li></ul><ul><li>Negative ch...
Implications for Growing   <ul><li>High CEC soils have more clay </li></ul><ul><li>Low CEC soils more sand </li></ul>
 
  Herbicide <ul><li>CEC determines how much herbicide should be used.  </li></ul><ul><li>Colloids absorb pesticides also, ...
Fertilization    <ul><li>High CEC soils have greater ability to hold nutrients - larger amounts, less frequently </li></ul...
  <ul><li>Golf courses - all sand - low CEC - fertilize lightly and often </li></ul><ul><li>Greenhouses - soilless - low C...
  <ul><li>Improve CEC by adding organic matter </li></ul><ul><li>Clay soils need less organic matter except to aerate soil...
NUTRIENT UPTAKE  
  Nutrient absorption   <ul><li>Nutrient ions cross cell membranes of root cells and move into vascular system </li></ul>
<ul><li>Some uptake is passive </li></ul><ul><li>Most uptake is active - takes energy to pull nutrients into high concentr...
  <ul><li>Roots produce energy by respiration </li></ul><ul><li>Waterlogged soil limits respiration -  limits nutrient upt...
  <ul><li>Root hairs get ions from soil solution by their own form of cation and anion exchange </li></ul>
  <ul><li>As root tips grow, move through solution, constantly finding more nutrients </li></ul>
  <ul><li>Capillary action moves nutrients through solution toward plant roots </li></ul>
  <ul><li>Diffusion  </li></ul><ul><li>moves ions through soil solution </li></ul><ul><li>–  higher concentration to lower...
Factors affecting uptake   <ul><li>Anything interfering with photosynthesis - slows growth, slows uptake   --low light --p...
 
Luxury Consumption  <ul><li>Plants can sometimes store nutrients  for when growth may be slowed </li></ul>
    <ul><li>Plants with deep roots, healthy roots need less fertilization </li></ul>
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Nutrients soil fertility

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Nutrients - Soil Fertility
Fruit and Vegetable Science
K. Jerome

Published in: Education

Transcript of "Nutrients soil fertility"

  1. 1. SOIL FERTILITY
  2. 2. <ul><li>Ability of soil to supply nutrients for plant growth   </li></ul>
  3. 3.     <ul><li>Soil is storehouse of nutrients   Some available, some not </li></ul>
  4. 4. Soil fertility:   <ul><li>quantity of nutrients soil contains </li></ul><ul><li>how well protected from leaching </li></ul><ul><li>how available to plant </li></ul><ul><li>how easily roots can take them up </li></ul>
  5. 5. Plant nutrients   <ul><li>Essential elements needed for plant growth </li></ul>
  6. 6. Plant nutrients <ul><li>Plants absorb 90 elements </li></ul><ul><li>Only a few needed for growth </li></ul><ul><li>Some not needed by plants but by animals that eat plants (cobalt) </li></ul><ul><li>Others not needed, can be toxic (lead) </li></ul>
  7. 8. <ul><li>How to determine which are essential? </li></ul>
  8. 9. Essential plant elements <ul><li>1. lack of element stops plant from growth or reproduction </li></ul><ul><li>2. element is directly involved in plant processes </li></ul><ul><li>3. shortage of element can only be corrected by supplying that element   </li></ul>
  9. 10. 17 essential elements   <ul><li>3 account for 95% plant needs </li></ul><ul><li>carbon, oxygen and hydrogen </li></ul><ul><li>come from water, air </li></ul>
  10. 11. Non-minerals         Macronutrients Air and Water Carbon (C)       Hydrogen (H)       Oxygen (O)
  11. 12. 14 come from soil   <ul><li>6 used in large amounts: </li></ul><ul><li>macronutrients </li></ul><ul><li>Nitrogen Calcium </li></ul><ul><li>Phosphorus Magnesium </li></ul><ul><li>Potassium Sulfur </li></ul>
  12. 13. Primary Macronutrients   <ul><li>Nitrogen Phosphorus Potassium </li></ul><ul><li>Not always available in large enough quantities </li></ul><ul><li>Add by fertilizing </li></ul>
  13. 14. Secondary Macronutrients   <ul><li>Calcium Magnesium Sulfur </li></ul><ul><li>Soil usually has plenty </li></ul>
  14. 15.   Micronutrients <ul><li>8 nutrients left </li></ul><ul><li>Used in small amounts </li></ul><ul><li>Plant won't grow normally without them </li></ul>
  15. 16.   NUTRIENT IONS <ul><li>Plants absorb some of the nutrients as ions instead of elements </li></ul><ul><li>Ion has positive or negative charge </li></ul>
  16. 17. <ul><li>Ion has: </li></ul><ul><ul><li>positive charge cation </li></ul></ul><ul><ul><li>negative charge anion </li></ul></ul>
  17. 18.   <ul><li>Ions form in soil when compounds dissolve in water   Example: </li></ul><ul><li>Potassium nitrate (fertilizer) dissolves in water, </li></ul><ul><li>molecule breaks down into potassium ion and nitrate ion </li></ul>
  18. 19.   <ul><li>Plant roots absorb ions - soak like a sponge </li></ul><ul><li>Soil particles adsorb ions - hold on to them - stick to it </li></ul>
  19. 21. SOURCES OF ELEMENTS IN SOIL <ul><li>Nutrient elements present in soil in four places (pools) </li></ul>
  20. 22. SOURCES OF ELEMENTS IN SOIL <ul><li>1. soil minerals </li></ul><ul><li>major source </li></ul><ul><li>released slowly by weathering </li></ul><ul><li>not source of nitrogen </li></ul><ul><li>  </li></ul>
  21. 23. SOURCES OF ELEMENTS IN SOIL <ul><li>2. organic matter </li></ul><ul><li>large amounts of nitrogen </li></ul><ul><li>nutrient anions </li></ul><ul><li>released by decay    </li></ul>
  22. 24. SOURCES OF ELEMENTS IN SOIL <ul><li>3. adsorbed nutrients </li></ul><ul><li>held by clay and humus particles </li></ul><ul><li>relatively available to plants </li></ul>
  23. 25. SOURCES OF ELEMENTS IN SOIL <ul><li>4. dissolved ions </li></ul><ul><li>ions in soil solution </li></ul><ul><li>plants absorb directly </li></ul><ul><li>may be leached </li></ul>
  24. 27. Soil colloids     <ul><li>Tiny particles of clay and humus with slight electrical charge </li></ul><ul><li>This charge attracts plant nutrient ions </li></ul>
  25. 28.   CATION EXCHANGE   <ul><li>Negative charge on soil colloids: </li></ul><ul><ul><li>attracts positively charge ions </li></ul></ul><ul><ul><li>repels negatively charged ions </li></ul></ul>
  26. 29. adsorption   <ul><li>Negatively charged colloid attracts swarm of cations from soil solution </li></ul>
  27. 32. Cation Exchange <ul><li>When one ion taken up by plant (pulled off soil particle), replaced by another. </li></ul><ul><li>Replacement of one cation for another </li></ul>
  28. 33.   <ul><li>Ability of soil to hold nutrients – </li></ul><ul><li>directly related to the number of cations it can attract to soil colloids </li></ul><ul><li>Determined by the amount of clay and humus in soil mix </li></ul>
  29. 34. <ul><li>Displacement of cations depends on: </li></ul><ul><li>Relative concentration </li></ul><ul><li>high concentration displaces low </li></ul><ul><li>The number of charges on a cation </li></ul>
  30. 35. high CHARGE displaces low Al>Ca>Mg>K>Na
  31. 37. <ul><li>Plant roots have negatively charged surfaces </li></ul><ul><li>positively charged hydrogen ions attached </li></ul><ul><li>Cation exchange takes place when plant roots exchange positive hydrogen ions for cations on soil colloids or in solution </li></ul>
  32. 38.   Cation Exchange Capacity (CEC) <ul><li>The ability of soil to hold exchangable ions </li></ul><ul><li>CEC expressed in milligram equivalents per 100 grams of soil (mEq/100g) </li></ul>
  33. 39.  
  34. 40. Bonding strength   <ul><li>If two cations are present in soil in equal numbers </li></ul><ul><li>one that bonds most strongly will be adsorbed </li></ul><ul><li>others will be leached out </li></ul>
  35. 41. Mass action  <ul><li>more ions in soil, </li></ul><ul><li>more exchange sites it will occupy </li></ul>
  36. 42.   <ul><li>Weakly held cations are more available for plant uptake </li></ul>
  37. 43. <ul><li>A clay particle is covered with negative charges </li></ul><ul><li>Opposites attract, ions with positive charge(s) stick all over surface of clay </li></ul><ul><li>root hairs secrete </li></ul><ul><li>H+ into water around clay particles </li></ul><ul><li>Smaller H cations </li></ul><ul><li>replace larger cations </li></ul>
  38. 44.   <ul><li>Several nutrients available to plants as negatively charged ions – anion exchange </li></ul><ul><li>Negative charge means it is repelled from cation exchange site </li></ul><ul><li>Anion exchange greatest in acid soils </li></ul>
  39. 45. Implications for Growing   <ul><li>High CEC soils have more clay </li></ul><ul><li>Low CEC soils more sand </li></ul>
  40. 47.   Herbicide <ul><li>CEC determines how much herbicide should be used. </li></ul><ul><li>Colloids absorb pesticides also, tie them up. </li></ul><ul><li>High CEC, clay soils usually need more to get effect you want </li></ul>
  41. 48. Fertilization   <ul><li>High CEC soils have greater ability to hold nutrients - larger amounts, less frequently </li></ul><ul><li>Low CEC - smaller amounts more frequently - leach out </li></ul>
  42. 49.   <ul><li>Golf courses - all sand - low CEC - fertilize lightly and often </li></ul><ul><li>Greenhouses - soilless - low CEC - fertilize lightly and often </li></ul>
  43. 50.   <ul><li>Improve CEC by adding organic matter </li></ul><ul><li>Clay soils need less organic matter except to aerate soil </li></ul>
  44. 51. NUTRIENT UPTAKE  
  45. 52. Nutrient absorption   <ul><li>Nutrient ions cross cell membranes of root cells and move into vascular system </li></ul>
  46. 53. <ul><li>Some uptake is passive </li></ul><ul><li>Most uptake is active - takes energy to pull nutrients into high concentration already in plant   </li></ul>
  47. 54.   <ul><li>Roots produce energy by respiration </li></ul><ul><li>Waterlogged soil limits respiration - limits nutrient uptake </li></ul>
  48. 55.   <ul><li>Root hairs get ions from soil solution by their own form of cation and anion exchange </li></ul>
  49. 56.   <ul><li>As root tips grow, move through solution, constantly finding more nutrients </li></ul>
  50. 57.   <ul><li>Capillary action moves nutrients through solution toward plant roots </li></ul>
  51. 58.   <ul><li>Diffusion </li></ul><ul><li>moves ions through soil solution </li></ul><ul><li>– higher concentration to lower concentration </li></ul>
  52. 59. Factors affecting uptake   <ul><li>Anything interfering with photosynthesis - slows growth, slows uptake   --low light --poor drainage --soil compaction --dry soils --soil temperature </li></ul>
  53. 61. Luxury Consumption <ul><li>Plants can sometimes store nutrients for when growth may be slowed </li></ul>
  54. 62.     <ul><li>Plants with deep roots, healthy roots need less fertilization </li></ul>
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