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Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
Nutrients   soil fertility
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Nutrients soil fertility

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Nutrients - Soil Fertility …

Nutrients - Soil Fertility
Fruit and Vegetable Science
K. Jerome

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  • 1. SOIL FERTILITY
  • 2. <ul><li>Ability of soil to supply nutrients for plant growth   </li></ul>
  • 3.     <ul><li>Soil is storehouse of nutrients   Some available, some not </li></ul>
  • 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. Plant nutrients   <ul><li>Essential elements needed for plant growth </li></ul>
  • 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. &nbsp;
  • 8. <ul><li>How to determine which are essential? </li></ul>
  • 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>
  • 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>
  • 11. Non-minerals         Macronutrients Air and Water Carbon (C)       Hydrogen (H)       Oxygen (O)
  • 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>
  • 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>
  • 14. Secondary Macronutrients   <ul><li>Calcium Magnesium Sulfur </li></ul><ul><li>Soil usually has plenty </li></ul>
  • 15.   Micronutrients <ul><li>8 nutrients left </li></ul><ul><li>Used in small amounts </li></ul><ul><li>Plant won&apos;t grow normally without them </li></ul>
  • 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>
  • 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>
  • 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>
  • 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>
  • 20. &nbsp;
  • 21. SOURCES OF ELEMENTS IN SOIL <ul><li>Nutrient elements present in soil in four places (pools) </li></ul>
  • 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>
  • 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>
  • 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>
  • 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>
  • 26. &nbsp;
  • 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>
  • 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>
  • 29. adsorption   <ul><li>Negatively charged colloid attracts swarm of cations from soil solution </li></ul>
  • 30. &nbsp;
  • 31. &nbsp;
  • 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>
  • 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>
  • 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>
  • 35. high CHARGE displaces low Al&gt;Ca&gt;Mg&gt;K&gt;Na
  • 36. &nbsp;
  • 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>
  • 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>
  • 39.  
  • 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>
  • 41. Mass action  <ul><li>more ions in soil, </li></ul><ul><li>more exchange sites it will occupy </li></ul>
  • 42.   <ul><li>Weakly held cations are more available for plant uptake </li></ul>
  • 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>
  • 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>
  • 45. Implications for Growing   <ul><li>High CEC soils have more clay </li></ul><ul><li>Low CEC soils more sand </li></ul>
  • 46. &nbsp;
  • 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>
  • 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>
  • 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>
  • 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>
  • 51. NUTRIENT UPTAKE  
  • 52. Nutrient absorption   <ul><li>Nutrient ions cross cell membranes of root cells and move into vascular system </li></ul>
  • 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>
  • 54.   <ul><li>Roots produce energy by respiration </li></ul><ul><li>Waterlogged soil limits respiration - limits nutrient uptake </li></ul>
  • 55.   <ul><li>Root hairs get ions from soil solution by their own form of cation and anion exchange </li></ul>
  • 56.   <ul><li>As root tips grow, move through solution, constantly finding more nutrients </li></ul>
  • 57.   <ul><li>Capillary action moves nutrients through solution toward plant roots </li></ul>
  • 58.   <ul><li>Diffusion </li></ul><ul><li>moves ions through soil solution </li></ul><ul><li>– higher concentration to lower concentration </li></ul>
  • 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>
  • 60. &nbsp;
  • 61. Luxury Consumption <ul><li>Plants can sometimes store nutrients for when growth may be slowed </li></ul>
  • 62.     <ul><li>Plants with deep roots, healthy roots need less fertilization </li></ul>

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