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Soil Health - a root-centric perspective

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Soil Health - a root-centric perspective

  1. 1. Soil Health 101 Joel Gruver WIU Agriculture A root-centric perspective
  2. 2. Big Hugh, how long will it take to win the war against soil erosion?
  3. 3. (2008) >70yearslater
  4. 4. Reducing erosion rates to T levels is just the beginning of good soil management. Well managed soil should deliver nutrients and water to plants when they need them and keep nutrients out of surface and ground water. Well managed soil should minimize the effects of floods and droughts. Well managed soil should resist compaction and other forms of degradation. By focusing soil conservation on enhancing soil function instead of preventing erosion, the goal is soil improvement as opposed to TOLERABLE DEGRADATION.
  5. 5. Go beyond T - Manage for C!
  6. 6. Do you recognize this soil health advocate?
  7. 7.
  8. 8. Grinnell Heritage Farm, owned and operated by Andy and Melissa Dunham, has grown from three acres in 2007 to 22 acres today and produces more than 60 varieties of certified organic plants and vegetables. The Dunham’s understand that the health of their soil translates into healthier crops and a more resilient farm. A fifth-generation farmer on the Grinnell farmland, Andy has made improving the health of the farm’s soil a major priority. “Our philosophy is feed the soil, it will feed your plants, and then it will feed us,” he said. Read more or watch the three-minute video profile:Grinnell Heritage Farm.
  9. 9. Do you recognize any of these CC innovators?
  10. 10. Is this really possible?
  11. 11. Sound management of variable soils requires a balanced approach – the causes of variability can be managed as well as the effects
  12. 12. WHY? Variation in INHERENT soil properties Variation in DYNAMIC soil properties Variation in crop management Variation in combine operation Large spatial variation in crop yield is common Striping is normally man-made!
  13. 13. Properties Ephemeral soil properties?
  14. 14. Have you observed this type of contrast on your farm? Same soil type Crop field Fence row
  15. 15. This past fall, students in my Soil Properties class brought in paired (Crop field & Fence Row) soils from their family’s farm. In most cases, the fence row soils had higher carbon dioxide and ammonia production.
  16. 16. Most kits sit idle in closets  A blast from the past 
  17. 17. What do the analytical results tell us? More informed decision making???
  18. 18.
  19. 19. Soil Health and Soil Quality are NOT synonymous
  20. 20. Variation in inherent soil properties
  21. 21. ≠ Soils like cars have inherent differences that are not changed by normal management Thin A horizon Thick A horizon Ca depleted sub-soil Ca rich sub-soil claypan no claypan
  22. 22. USDA Textural triangle 12 textural classes Texture is generally considered an inherent soil property
  23. 23. >12 “ 10-12” 8-10” 6-8” < 6” Variation in texture is directly related to variation in plant available water
  24. 24. Which soil texture holds the most plant available water? Adapted from Kramer 1983
  25. 25. Predicted Soil Hydrologic Properties The calculator predicts soil hydrologic properties based on soil texture as well as modulating factors: OM, salinity, gravel content and compaction Based on data from ~ 2000 soil samples
  26. 26. x 0.47 -> x 3.4 ->
  27. 27. In addition to texture, soil/crop management systems impact the 1) movement of water, 2) storage of water, and 3) volume of soil from which crop roots acquire water. So how should we target our management to most improve crop access to water?
  28. 28. x 1.10 -> x 2.5 ->
  29. 29. x 0.88 -> x 0.14 ->
  30. 30. x 0.75 -> x 0.32 ->
  31. 31. Water movement (infiltration vs. run-off) and depth/volume of soil from which crop roots acquire water are much more sensitive to management than water holding capacity
  32. 32. Management decisions influence both 1)CROP ROOTING POTENTIAL 2) SOIL CONDITIONS Less of a particular crop/cover crop’s rooting potential is realized when soil conditions impede root growth and function. Physical factors – compaction, poor drainage, high or low temperature Chemical factors – acidity/metal toxicities, nutrient deficiency/excess, salinity Biological factors – root herbivores/pathogens
  33. 33. Effectiveness of in-field conservation practices should be assessed with respect to impact on root growth and function NOT tons of soil loss.
  34. 34. Soil/crop management strategies for optimum root growth and function • Alleviate existing physical, chemical and/or biological barriers to root growth • Prevent development of physical, chemical and/or biological barriers to root growth • Plant crops on soils for which they are well adapted • Grow strategic sequences of crops/cover crops to maximize a positive cycle of root zone improvement •Treat seeds/roots with biological inoculants to enhance root-enhancing biological relationships
  35. 35. Acute root disease  Chronic Root Malfunction  VS. Chemical, physical and biological factors cause CRM! is the norm in agriculture
  36. 36. Seed treatments can prevent acute root disease and insect feeding but do not solve the problem of CRM
  37. 37. STEEP, DEEP and CHEAP Breeding goals proposed by J. Lynch RCA = Root cortical aerenchyma We can breed crops with more robust roots!
  38. 38. Three primary factors affecting flooding tolerance in plants have been reported: (1) the ability to grow adventitious roots at the soil surface during flooding; (2) the capacity to form root aerenchyma; and (3) tolerance to toxins (e.g., Fe 2+, H2S) under anaerobic soil conditions. By analyzing these components separately, it should be possible to perform selections for genotypes exhibiting varying degrees of flooding tolerance.
  39. 39. Increased efficacy of symbiotic N fixation can be achieved by selecting not only better bacteria but by selecting the best combinations of host plants and bacteria. …targeted efforts to select superior plant:microbe partners will bring benefits under a wider range of environmental conditions.
  40. 40. We are conducting trials of AZ-Green from TerraMax
  41. 41. competition parasitism antibiosis induced resistance 4 main types of microbial interactions that promote root health Sales reps should know how their biological products work
  42. 42. Dramatic effect of the inclusion of compost in potting media on the health of pepper roots
  43. 43. Aluminum toxicity Aluminum toxicity Chemical toxicities inhibit root growth & function Al toxicity is very common in the SE US and in tropical countries like Brazil
  44. 44. Nutrient availability affects root growth but affects top growth more
  45. 45. N and P promote root branching and proliferation
  46. 46. Ontario Ministry of Ag and Food Why do crops on tiled-drained land tend to be more drought resistant ?
  47. 47. Ontario Ministry of Ag and Food Do crop roots grow toward water? Roots elongate directed by gravity in AEROBIC soil!
  48. 48. Air pruning promotes root branching
  49. 49. Soil block system for growing tomato transplants Air pruning promotes root branching No root spiraling
  50. 50. Soil can get too hot for optimal root growth! Soil aeration also affects soil temperature which strongly affects root growth rate
  51. 51. Brady and Weil (2002)Brady and Weil (2002) Sub-soil water and nutrients Compaction strongly impacts root growth and function
  52. 52. Adapted from Hunt et al. (1986) Tillage can positively and negatively affect root growth and function
  53. 53. Long term no-till (w/ healthy soil biology) Intensive tillage Ontario Ministry of Ag and Food Plow pan Network of cracks and biopores
  54. 54. Annual ryegrass roots penetrating > 40” Radish roots > 40” after 1.5 months
  55. 55. Land preparation vs. Soil Preparation
  56. 56.
  57. 57.
  58. 58.
  59. 59. How regularly do you look at roots?
  60. 60. You really won’t know what is happening underground unless you take a look…
  61. 61. All you need is a shop-vac and a hose :-> ! Its just like going to the dentist!
  62. 62. Healthy shoot growth and high yields white color proliferate in all directions extensive growth into the sub-soil minimal evidence of deformities Efficient use of soil resources What should you look for?
  63. 63. Not all healthy roots are white in color!!
  64. 64. How is it possible for healthy crops to grow with such a limited rooting volume?
  65. 65. Wading pools do NOT provide an optimal rooting zone but a small root system can support healthy shoot growth with ample moisture and nutrition.
  66. 66. ?
  67. 67. Mural on my shed inspired by JE Weaver’s illustrations I have heard people say that horticultural crops just have wimpy inefficient root systems…
  68. 68. rootdevelopment.pdf
  69. 69. Lettuce roots after 3 weeks The roots on the right were grown in compacted soil, the roots on the left were grown in soil with good structure. 1ft
  70. 70. Extensive root system of a flowering lettuce plant 5’
  71. 71. Asparagus root system after 6 years 10 feet
  72. 72. Depth (ft) %sand %silt %clay 0-0.5 31 34 35 0.5-1 33 29 38 1-2 23 31 47 2-3 20 31 49 3-4 22 34 44 4-5 25 37 37 Soil particle size variation with depth at Dr. Weaver’s research farm (Lincoln, NE) This is not a sandy soil!
  73. 73.
  74. 74. Crop Sensitivity Rooting Impact of drought Moisture to drought Depth Management
  75. 75. Shallow broccoli onion Irish potato Medium green beans edamame beet carrot cantaloupe cucumber eggplant pepper summer squash Deep lima beans lettuce okra parsnip pumpkin winter squash tomato watermelon Relative root depths of vegetable crops (according to Dr. Sanders’ bulletin) Partly a function of length of growing season/timing of harvest
  76. 76. ASM = Available Soil Moisture = % of water between field capacity and wilting point Key info for scheduling irrigation
  77. 77. Tensiometer
  78. 78. Vegetable crops normally leave more residual N both in crop residues and as mineral N than grain crops. While much of this N may be dissipated into the environment before the next crop, high mineral N (nitrate + ammonium) values are commonly found in the spring after vegetable crops. Mineral N retained from the previous year is mostly found in deeper soil layers. Therefore, choosing crops with deep root systems is key to utilizing N retained from previous crops. Large differences in the ability to take up N from deeper soil layers are found among vegetable crops.
  79. 79. 0 - 18” 18 - 36” 36” - 54” 0 55 110 165 Only 55% of N in root zone of following crop Veg crop sequences with poor N utilization lbs of N per acre (spring after preceding crop) Precedingcrops Followingcrops Rooting depth Rooting depth Rooting depth 0 – 1.5’ 3’- 4.5’1.5’ – 3’
  80. 80. 0 - 18” 18 - 36” 36” - 54” 0 55 110 165 85% of N in root zone of following crop Veg crop sequences with high N utilizationPrecedingcrops Followingcrops Rooting depth Rooting depth Rooting depth 0 – 1.5’ 3’- 4.5’1.5’ – 3’ lbs of N per acre (spring after preceding crop)
  81. 81. What are these crazy people trying to do ? Location: Laurenburg, NC Date: 1961 Trying unsuccessfully to change an old highly weathered soil in North Carolina into a deep fertile “Prairie” soil
  82. 82. The giant plow on the previous slide was designed for burying flood sediment
  83. 83. The advantage of the USGA green is its long-term research-base and proven performance in the field. If properly built and maintained, golfers rarely face poor putting conditions. The biggest drawback is collecting the necessary materials and the cost of construction. One USGA green costs ~$40,000 to construct. Sometimes it makes sense to dramatically modify soil inherent properties
  84. 84. The current OM level in a soil is a result of the long-term balance between organic inputs and outputs Yield enhancing practices will not build SOM if losses increase at a comparable rate Organic outputs
  85. 85. ”But with the removal of water through furrows, ditches, and tiles, and the aeration of the soil by cultivation, what the pioneers did in effect was to fan the former simmering fires… into a blaze of bacterial oxidation and more complete combustion. The combustion of the accumulated organic matter began to take place at a rate far greater than its annual accumulation. Along with the increased rate of destruction of the supply accumulated from the past, the removal of crops lessened the chance for annual additions. The age-old process was reversed and the supply of organic matter in the soil began to decrease instead of accumulating.” William Albrecht – 1938 Yearbook of Agriculture Drainage + Tillage + Lime + N + harvest = Accelerated loss of SOM
  86. 86. Soil Changes After Sixty Years of Land Use in Iowa Jessica Veenstra, Iowa State University, 1126 Agronomy Hall, Iowa State University, Ames, IA 50010 Soils form slowly, thus on human time scales, soil is essentially a non- renewable resource. Therefore in order to maintain and manage our limited soil resources sustainably, we must try to document, monitor and understand human induced changes in soil properties. By comparing current soil properties to an archived database of soil properties, this study assesses some of the changes that have occurred over the last 60 years, and attempts to link those changes to natural and human induced processes. This study was conducted across Iowa where the primary land use has been row crop agriculture and pasture. We looked at changes in A horizon depth, color, texture, structure, organic carbon content and pH. Hill top and backslope landscape positions have been significantly degraded. Catchment areas have deeper topsoil.
  87. 87. OM enriched sediment OM depleted top soil
  88. 88. Redistribution of topsoil is an expensive but potentially highly effective method of improving root growth and function. Soil landscape restoration involves moving soil from areas within a field where it has accumulated through erosion to areas where it has been lost through erosion. Strategic redistribution of topsoil - ranging from raised beds to reuse of dredge materials - merits consideration, especially in high value horticultural crop production
  89. 89. Perennial-based rotation systems Tree crops Permanent pasture systems Winter cover crops Green Lands = Blue Waters Conservation Cropping Systems
  90. 90. Soil Health is Not an End in Itself The ultimate purpose of researching and assessing soil health/quality is not to achieve high aggregate stability, biological activity, or some other soil property. The purpose is to protect and improve long-term agricultural productivity, water quality, and habitats of all organisms including people. We use soil characteristics as indicators of soil health, but in the end, soil health must be identified by how well soil performs its functions.