Basic soil improvement


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I shared this presentation on 1/21/2011 at the SSAWG conference in Chattanooga, TN

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Basic soil improvement

  1. 1. Basic Soil Improvement Techniques for Sustainable Farmers Dr. Joel Gruver School of Agriculture Western Illinois University (309) 298 – 1215
  2. 2. Useful Resources
  3. 3.
  4. 4. Managing cover crops profitably, 3rd edition
  5. 5. Free downloads
  7. 7. Excellent comprehensive soil science textbook> $100 < $10
  8. 8. Are you Which factorfamiliar with do you think isthe “disease most triangle”? important?
  9. 9. Do you think agroecologically?
  10. 10. Continuous tomatoes Managing crop residuesAll of these strategies are being used successfully by some farmers/gardeners. Only you can determine the best fit for you.
  11. 11. Growing under cover may be the most effective organic strategy for improving crop health and productivity
  12. 12. Have any of you visited Monticello ? Jefferson made good use of microclimates
  13. 13. Thomas Jefferson Garden in GruverlandInspired by Monticello, my family decided to make better use of microclimates
  14. 14. Understanding the soil environment
  15. 15. Sand and siltare the bones of the soil skeleton Soil skeletons
  16. 16. Clay and humus are the soil skin and connective tissues Brady and Weil (2002) minerals humus
  17. 17. Why is the soil skin important ?  Adsorption of water films  Adsorption of organic and inorganic chemicals  Ion exchange  Catalysis of chemical reactions  Habitat for bacteria
  18. 18. Get toknow yoursoil’s body parts !
  19. 19. The jar test
  21. 21. Textural 12triangle textural classes
  22. 22. Loamy soilsLoamy soils have the most favorable physical properties
  23. 23. Potting media criteriaHigh moisture retention and rapid drainageIt can be difficult toeffective for both It is rarely cost optimizemoisturefarmers to change the texture retention and drainage in or other inherent properties ofreal soils the soils on their farms
  24. 24. ≠Understanding inherent differences in soil properties
  25. 25. WEB SOIL SURVEY- a great source of info on soil inherent properties
  26. 26. What are these crazy peopletrying to do ? Location: Laurenburg, NC Date: 1961 Very deep plowing aspart of a futile effort to create deep “Prairie”soils in North Carolina
  27. 27. Good Tilth Poor Tilth The soil fabric
  28. 28. The soil pore network serves as a respiratory and circulatory system
  29. 29. Understanding your soil’s respiratory and circulatory system Pore size Drainage pores 10- 30 μm Field Capacity Easily available Plant available water Permanent wilting point 0.2 μm Unavailable water Adapted from Buol (2000)
  30. 30. 1.0% CAfter adding water 1.4% C
  31. 31. Do youscavenge andhoard organicmaterials fromfar and wide?
  32. 32. This can be a good soil building strategy but should not be apermanent strategy in aworld with finite organic resources.Is it time to reduce your farm’s foot print?
  33. 33. What is happening on your farm? There is a lot more to soil organic matter management than just increasing OM inputs !!
  34. 34. Why does org anic matteraccumulate in soil?
  35. 35. Most soil microbes are unculturable
  36. 36. ..and the soil microbes that are culturable can digest almost everything organic at rates hundreds of times faster thandecomposition in field soils
  37. 37. aka digestibilityUnderstanding organic resource quality C:N ratio > ~ 20 (Giller, 2000)
  38. 38. Relationship between fine mineral fraction and SOM Soils with more fine particles normally retain more SOM Magdoff and Weil (2004)
  39. 39. Weak relationship between clay content and SOC for 1261 agricultural soils in England and Wales Clearly many factors other than clay affect C accumulation Webb et al.(2003)
  40. 40. Temperature affects SOM dynamics Organic matter destruction by aerobic organisms Your farm and consumption in 50 yrs Organic matter Organic matter consumption OM production production synthesis by plants ~ 70 F mean annual temp TemperatureBrady and Weil (2002)
  41. 41. Landscape position affects SOM dynamicsPoorlydrained Where does the most OM accumulate? Interstream divide Somewhat Moderately LANDSCAPE poorly well drained drained POSITIONS Well drained Poorly Shoulder Interfluve drained Valley floor SOIL Backslope DRAINAGE CLASSES
  42. 42. Agriculture normally accelerates loss of SOM
  43. 43. OM depleted top soilErosion has caused major redistribution of OM OM enriched sediment
  44. 44. Artificial drainage has greatly increased the number of days when soils are suitable for field operations but has also contributed Pollution of to manywater resources environmental Loss of SOM problems
  45. 45. 4742 Identify 2 methods of increasing SOM. Adapted from Magdoff and Weil (2003)
  46. 46. Small increases in OM can improve macro-aggregation Superior air/water relationships Healthier root growth and function (justification statement)NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE
  47. 47. There’s more than one way to collect a soil sample but results have little value if the sample is not representative
  48. 48. Composite samplingMultiple sub-samples arecollected fromeach managementunit and mixedtogether
  49. 49. Recommendations Analytical results So what do thenumbers mean ???
  50. 50. Have any of you ever had to run a 40as part of a try-out for a team? How well does an athlete’s 40 time predict their ability to play the game?
  51. 51. By themselves, extractable nutrient levels are not informative. Extractable nutrient levels provide an index ofnutrient availability that can be interpreted using results from field experiments.
  52. 52. Meaningful interpretation of soil test results requires field calibration100 %yield 50 % yield Soil test P concentration (ppm)
  53. 53. moisture temperature microbial activitySoil test levels are not directly related to most of the factors controlling nutrient availability during a growing season. Calibration experiments were not conducted using organic management practices rooting depth root health
  54. 54. Understanding nutrient uptake Root H20 exudates Transpirationalactivate soil stream microbes H 20 Root growth
  55. 55. that are not Nutrients that can be easily redistributed easily redistributed
  56. 56. Sampling vegetable crops for tissue analysis
  57. 57. Analytical results Estimated Nutrients available for a single cropTotal nutrient content of DM is adjusted for moisture and availability
  58. 58. Feed the soil vs. Feed the crop ? Both strategies are important ! Unhealthy roots in soils with low SOM and poor structure use nutrients inefficiently… Healthy roots need available nutrients !Plants with poorly developed roots tend to havenutrient deficiency Acute rootand drought stress disease symptoms Chronic root malfunction
  59. 59. How oftendo you How oftenlook atlook do youroots ? at roots?
  60. 60.
  61. 61. Raised beds promote healthy roots !! Faster drainage and soil warming Greater depth of fertile soil Restricted traffic
  62. 62. No wheeltraffic on beds
  63. 63. What happened to my soil?? Tillage when a soil is too wet often creates clods that require a period of wetting and drying and/or freezing and thawing (in addition to biological activity) before good structure is restored.
  64. 64. Are you familiar with the fence post principle? Zone of maximum biological activity and rapid residue decay
  65. 65. The soil stomach Bacteria Plant roots depend Fungi Microflora on an external Algae digestive system Protozoa Microfauna “ the soil food web” Nematodes Microarthropods Mesofauna Enchytraeids Earthworms Ants, termites, spiders Macrofauna Mollusks Others: rodents, snakes, Megafauna voles, amphibians, etc.
  66. 66. What do bacteria do in soil ? Colonize aerobic and anaerobic environments Decompose easily digested organics Mediate redox transformations Nourish bacterivores Fix N
  67. 67. Most N transformations in soil are carried out by bacteria!! SoilPlant biomass
  68. 68. What do fungi do in soil ? Decompose less easily digested organics Penetrate residues Stabilize soil structure Nourish fungivores Form symbioses with plant roots and soil fauna Compete with plant pathogens Parasitize plants and soil animals Produce toxins e.g. aflatoxin produced by Aspergillus flavus on peanut
  69. 69. Most plant pathogens arefungi but most fungi are not plant pathogens !!
  70. 70. Soil organisms in areconcentrated HOT SPOTS ! detritusphere rhizosphere Adapted from Coleman et al. (19??)
  71. 71. Detrituspheresurface residue zone
  72. 72. Clean tillageeliminates thedetritus layer Many soil organisms prefer to feed at the surface
  73. 73. Rhizosphere < 10 % of soil volumeunder prairie vegetation< 1 % of soil volume under most vegetable crops Zone of root influence
  74. 74. Cover crops Less loss Less loss
  75. 75. Cover crops increase annual root production and function Feed livestock Cover Crops Recent studies indicate thatCCs can have many root production is the bestother beneficial predictor of long-termeffects Adapted from Magdoff and Weil (2004) retention of SOM.