Beyond "Dirt" - Garden Soil and Amendments

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Readying the soil for spring-summer planting is one of the most important tasks gardeners face at this point in the year. But what is soil made of, and what does it need to benefit the plants we want to grow? This class will provide an overview of soil types and basic soil ecology, give gardeners tools for assessing their soils, and provide suggestions on when and how to use various soil amendments.

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Beyond "Dirt" - Garden Soil and Amendments

  1. 1. Garden Soil & Amendments Independence Gardens Portland, OR January 2012 © Independence Gardens LLC Download the handout that goes along with this slideshow! http://bit.ly/y4K4ru Tuesday, January 31, 2012
  2. 2. Topics We’ll Cover • What is soil? • Soil issues worldwide • Soil issues in your garden • Soil components • pH • Nutrients • Soil testing • Amendments What We’ll Cover TodayPreview Got Questions? Please ask as we go along. Tuesday, January 31, 2012
  3. 3. What is soil? • Soil is an edge – Microorganisms + minerals • Soil is the basis of a diverse ecosystem – Broader base  more room for everything else • Soil is a process – Anything but static! • Soil is a relationship – Between components, conditions, inhabitants, and YOU http:// www.extension.um n.edu/distribution/ cropsystems/ images/ M1272-4.jpg http://www.hylandseeds.com/images/ soil%20photo.jpg Tuesday, January 31, 2012
  4. 4. Soil worldwide http://www.utafoundation.org/soil_loss.jpg Tuesday, January 31, 2012
  5. 5. Soil in your garden • Top 6-8 in. – Where plants do most of their feeding • You can look for – Structure – Texture – pH – Nutrient presence/availability – Organic matter – Biological activity • A single acre of good soil can support 2000 lbs. of animal life above the soil surface and 4000-6000 lbs. below (“microherds”) http://www.gardenvisit.com/assets/madge/shovel/600x/ shovel_600x.jpg Tuesday, January 31, 2012
  6. 6. Soil components • Mineral components and organic matter = “solid” • Air and water = “space” – Soil microorganisms live in this part of the soil, and they are what make nutrients available to plants http://courses.soil.ncsu.edu/resources/physics/ composition/compo3b.png Tuesday, January 31, 2012
  7. 7. http://school.discoveryeducation.com/schooladventures/soil/ images/particle_sizes1.gif Soil particles • Clay – Less than 0.002 mm • Silt – 0.002 mm – 0.05 mm • Sand – 0.05 mm – 2.00 mm • Fine pebbles – 2.00 mm – 5.00 mm • Medium pebbles – 5.00 mm – 20.00 mm • Coarse pebbles – 20.00 mm – 75.00 mm Tuesday, January 31, 2012
  8. 8. http://www.omafra.gov.on.ca/english/engineer/facts/ vfss_manual/vfssman37f1.png Soil layers • O (organic) • A (assimilation) • E (elluviation) • B (banking) • C (chemical/ constitution) • R/D (durable) Tuesday, January 31, 2012
  9. 9. Soil types • Not just “dirt” – Dirt is soil where it’s not supposed to be • Loam is ideal for garden soil – 40% silt – 40% sand – 20% clay http://www.dirtguytopsoil.com/images/soiltriangle.gif Tuesday, January 31, 2012
  10. 10. Soil food web • This is who/what shares your soil with your plants http://www.magicsoil.com/MSREV2/Soil_Food_Web_Soil_Biology_Primer.jpg Tuesday, January 31, 2012
  11. 11. pH • Logarithmic scale, 0 (acid)-14 (base) http://packerpedia.wiki.packer.edu/file/view/pH_Scale.jpg/31722773/pH_Scale.jpg Tuesday, January 31, 2012
  12. 12. Nutrient availability • Soil nutrient supermarket • Our soils are generally ~5.5 • Ideal garden soil is 6.8-7.0 • Other factors affecting availability include: – Soil texture – Soil temperature – Amount of organic matter – Microbial activity – Interactions with other nutrients • Competition for sites on soil particles • Forming insoluble compounds http://attra.ncat.org/images/organic_soil/chart.jpg Tuesday, January 31, 2012
  13. 13. Nutrient availability • Soil nutrient supermarket • Our soils are generally ~5.5 • Ideal garden soil is 6.8-7.0 • Other factors affecting availability include: – Soil texture – Soil temperature – Amount of organic matter – Microbial activity – Interactions with other nutrients • Competition for sites on soil particles • Forming insoluble compounds http://attra.ncat.org/images/organic_soil/chart.jpg Tuesday, January 31, 2012
  14. 14. Nutrient availability • Soil nutrient supermarket • Our soils are generally ~5.5 • Ideal garden soil is 6.8-7.0 • Other factors affecting availability include: – Soil texture – Soil temperature – Amount of organic matter – Microbial activity – Interactions with other nutrients • Competition for sites on soil particles • Forming insoluble compounds http://attra.ncat.org/images/organic_soil/chart.jpg Tuesday, January 31, 2012
  15. 15. Nutrients Tuesday, January 31, 2012
  16. 16. Essential plant nutrients • From air and water – Carbon (C) Hydrogen (H) Oxygen (O) • Macronutrients – Nitrogen (N) Phosphorus (P) Potassium (K) • Secondary macronutrients – Sulfur (S) Calcium (Ca) Magnesium (Mg) • Micronutrients – Boron (B) Chlorine (Cl) Copper (Cu) – Iron (Fe) Manganese (Mn) Molybdenum (Mo) – Zinc (Zn) Tuesday, January 31, 2012
  17. 17. How to learn more • Shake test – “Layer Away” • Perc test • Watering test • pH test • Soil test • “Weed” observation • Bug’s eye view Tuesday, January 31, 2012
  18. 18. Soil testing: Do it...if: • Nutrient testing – You plan to grow most or all of your own food yourself – You’re growing in a small, homogenous, contained space – and/or you’ve been experiencing problems • Toxics testing (esp. Pb) – You are aware of previous uses of your land that were “dirty” or sources of pollution in the ‘hood – You don’t know how your land has been used in the past – You’re growing within 6 ft. of a house built before 1978 – Small children/elders/animals will eat the harvest http://www.thegardenerseden.com/wp-content/uploads/2009/10/Soil- Sample-for-Testing.jpg Tuesday, January 31, 2012
  19. 19. What to do with your new info • Awareness...attention...and amendments! – Organic matter • Adding it is the most important thing you can do for your soil! • 1-2 times a year, add 1-2 in. of compost, mixed into the top 8 in. of soil – Soil conditioners improve structure and/or provide nutrients • Examples: coffee grounds, bloodmeal, kelp, peat moss, coco coir, lime, etc. (some are organic matter, some are not) • Apply as needed – Mulches have many benefits but are not soil conditioners – Fertilizers aren’t designed to help your soil Tuesday, January 31, 2012
  20. 20. Adding organic matter • Increases infiltration of water from soil surface • Increases water-holding capacity in sandy soils and drainage in clay soils • Improves nutrient retention (reduces leaching) • Improves nutrient availability • Examples: garden/household compost, (composted) manure, mushroom compost, cover crops/green manure, worm castings Tuesday, January 31, 2012
  21. 21. Changing pH • Test first – DIY kits – Professional/lab test • To raise pH – Add lime (maximum: 5 lbs./100 sq. ft.) – Add wood ash (maximum: 1.5 lbs./100 sq. ft./yr.) • To lower pH – Add organic matter – Add sulfur (maximum: 5 lbs./100 sq. ft.) Tuesday, January 31, 2012
  22. 22. Ongoing nutrition • Know what’s there already • Conserve what is present – Maintain pH – Reduce erosion and leaching – Recycle nutrients! (compost/mulch) • Add nutrients – Commercial/packaged fertilizers • Avoid fertilizing dry soil • Always follow instructions on the label – Organic matter • Include cover crops/green manures to protect and enhance soil Tuesday, January 31, 2012
  23. 23. Organic fertilizer N-P-K values Thanks to Naomi Montacre for this chart. Tuesday, January 31, 2012
  24. 24. A few more pointers • Define your garden space – One way to do this: use raised beds – Or…you can use containers • This is a whole different kind of soil and soil-building • Avoid compaction – Including mechanical tilling • Avoid unnatural layering – For example, infilling a raised bed and not incorporating the new soil into the native soil • A note on toxins – Know where the risk is and the common pathways for exposure Tuesday, January 31, 2012
  25. 25. And finally... • To get neglected soil into shape for THIS season – Incorporate 1-6” of compost – Add kelp meal (K), bone meal or a mineral mix (P), and an organic N source (alfalfa meal, blood meal, or fish meal/emulsion) according to package instructions • To protect your soil for next year – Mulch regularly – Sheet mulch or cover crop through the winter Tuesday, January 31, 2012
  26. 26. Questions? Tuesday, January 31, 2012

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