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Soils 101 for High Tunnels 2012
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Soils 101 for High Tunnels 2012


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by Peter Bierman and Carl Rosen. Presented at the 2012 MN Statewide High Tunnel Conference.

by Peter Bierman and Carl Rosen. Presented at the 2012 MN Statewide High Tunnel Conference.

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  • 1. Soils 101: Soil Physical & Chemical Properties Peter Bierman and Carl Rosen Department of Soil, Water, and Climate University of MinnesotaMFVGA Beginning Grower Workshop January 18, 2012
  • 2. Physical Propertiesl Texture, structure, organic matterl Controls drainage, water-holding capacityl Suitability for vegetable/fruit productionl Often the most difficult to manage
  • 3. Soil Testing and Soil Fertilityl Essential plant nutrientsl Managing fertilityl Soil acidity and limingl Types of soil testsl Soil sampling/sample handlingl Fertilizer sources
  • 4. Soil Composition Soil is composed of solids, water, and air  Solids (50%)  Sand, silt, clay (90-99%)  Organic matter (1-10%)  Water (25%)  H 2O  100-1000 ppm soluble salts  Air (25%)  High CO2 (10-20 times as high as the atmosphere)
  • 5. Importance of Soil Physical Propertiesl Healthy crop root growth q roots require both air and waterl Determines infiltration, drainage, aeration, water-holding capacity q control the balance between air and water in the root zone
  • 6. Soil Texturel Relative proportions of sand-, silt-, and clay-sized particles q sand > silt > clayl Soil “textural class” q loamy sand, silt loam, clayl Texture is a fixed soil property q not altered by management under ordinary conditions
  • 7. Soil Texturel Coarse-textured soils q dominated by sand • well-drained/aerated • low water and nutrient holding capacityl Fine-textured soils q dominated by clay • poorly drained/aerated • high water and nutrient holding capacityl Loams q intermediate texture and properties
  • 8. Textural Triangle Feel
  • 9. Soil Structurel Sand, silt, clay combined into aggregatesl Aggregates arranged with pore spaces between theml “Good” structure q ~50% solids and 50% pore space q pore space evenly distributed • large, air-filled pores (drain readily) • smaller, water holding pores
  • 10. Soil Structure Soil Air & Water Tightly Held Water Film Water-filled Pore Space Air-filled Macropore Soil Aggregate
  • 11. Soil Structure l Soil structure can be altered by management q improved or degradedGranular aggregation promoted Compaction reduces pore spaceby organic matter
  • 12. Soil Organic Matter Organic matter affects most soil properties  Forms of organic matter • Plant/animal residues • Various stages of decomposition • Humus • Decomposition by-product • Resistant to further degradation
  • 13. Soil Organic Matterl Can improve aggregation and structurel High water-holding capacityl Improves physical condition of both coarse- and fine-textured soilsl Retains and cycles nutrientsl Drives soil biology
  • 14. Soil Depthl Determines potential rooting depthl Zone of water and nutrient uptakel Drainage restrictionl Gravel, bedrock, compacted layers
  • 15. Finding Soil/Site Informationl County Soil Surveys q soil maps q soil types q texture q drainage q topography q water-holdingl NRCS, SWCD, Extensionl SoilWeb Appl
  • 16. Soil Survey
  • 17. Soil Survey
  • 18. Site Preparation/Modificationl Ideally begins well before planting the first vegetable crop Subsurface Drainage and Crop Root Growthl Drainage improvements Free water level Free water level Free water level Free water level Spring Summer Spring Summer Undrained Land Tile Drained Land
  • 19. Site Preparation/Modificationl Increase soil organic matter q high residue rotation crops q cover crops q manure, compostl Soil test q lime q fertilizer
  • 20. Soil Testing and Soil Fertilityl Essential plant nutrientsl Soil sampling/handlingl Types of soil testsl Soil acidity and limingl Cation exchange capacityl Organic/inorganic fertilizersl Value of soil testing q example field
  • 21. Essential Plant NutrientsNutrients derived from the soil and/or fertilizer Macronutrients Micronutrients Primary Zn – Zinc N - Nitrogen B – Boron P – Phosphorus Fe – Iron K – Potassium Mn – Manganese Secondary Cu – Copper S – Sulfur Mg – Magnesium Mo – Molybdenum Ca – Calcium Ni – Nickel Cl – Chlorine
  • 22. Soil Samplingl Collect representative samples q Soil tests are only as accurate as the samples you submit q Sampling is often the weakest link in a soil testing programl Follow sampling and handling guidelines of the laboratory you submit samples to
  • 23. Sampling Guidelinesl Divide fields into uniform areas q soil type, slope, crop history, tillage, previous lime, fertilizer, manure, compost applicationsl No more than 20 acres for a single samplel Collect 20-30 soil cores q random, zig-zag pattern across the fieldl Standard depth 6-8 inches q 2 feet for soil nitrate test
  • 24. Soil Samplingl Thoroughly mix sub-samples in a clean, plastic container q submit about a pint of this composite sample to a laboratory for analysisl If soil is wet q air dry • spread in a thin layer on a clean surface before mixing q oven dry at <97° F
  • 25. Soil Testsl Standard series q do on a regular basis q P, K, soil pH, buffer pH, OM, texture • lime requirements are based on a Buffer Indexl Additional tests q first time a new site is sampled • or when a problem is suspected q Ca, Mg, Zn, B • Cu and Mn on organic soils
  • 26. SherburnePine Hill Vineyard 123 Needle Lane 48 Big Lake, MN 55309 1 57 57 x x x 2 25 57 x x x xx
  • 27. 03/20/2005
  • 28. Soil Acidityl Soil pH measures acidity/alkalinityl Mineral soils q pH 5.8 to 7.0 • optimum range for most vegetables q pH of 5.4 or less reduces scab on potatoesl Organic soils (peats and mucks) q optimum pH is lower, 5.2 to 6.0
  • 29. Soil pHl Microbial activityl Nutrient availability q optimum pH about 1 unit lower for organic soils/media Mineral soils
  • 30. Limingl Soil acidification q rainfall and leaching, N fertilizersl Western MN vs. eastern MNl Soil pH q do you need lime?l Buffer index q reserve acidity q how much lime?
  • 31. Nitrogenl Recommendations based on q crop grown • expected yield q soil organic matter level q preceding legume crops q manure or compost applications q nitrate soil test • measures residual N • standard in western MN
  • 32. Phosphorus and Potassiuml Recommendations based on q crop grown • expected yieldl Soil test level for P and K
  • 33. Relative Nutrient Mobilityl Nitrogen moves much faster than phosphorus and potassium in the soill Phosphorus has very limited mobility in the soill Implications: q P and K should be incorporated before planting q Nitrogen can be topdressed or sidedressed during the growing season
  • 34. Soil Cation Exchange Capacity CEC is the amount of positively charged ions a soil can hold – reduces leaching and buffers the soil solution Soil Solution K+ Mg2+ Ca2+ H+
  • 35. Sources of Plant Nutrients Plant nutrients come from both organic and chemical sources
  • 36. Organic vs. Inorganic Fertilizersl Organic q Nutrients slowly released q Low burn potential q Improve soil structure q May contain weed seeds q Usually higher cost q Acceptability for certified organic crop production depends upon the certifying agencyl Inorganic (manufactured soluble fertilizers) q Nutrients quickly available q High burn potential q Lower cost/unit of nutrient
  • 37. Inorganic FertilizersInorganic Fertilizer %N % P2O5 % K2O___________________________________________________________________________________________________________Ammonium sulfate 21 0 0Ammonium nitrate 34 0 0Urea 45 0 0Calcium nitrate 15 0 0Monoammonium phosphate 11 48 0Diammonium phosphate 18 46 0Rock phosphate 0 5 0Superphosphate 0 20 0Conc. superphosphate 0 46 0Green sand 0 1 6Muriate of potash 0 0 60Potassium sulfate 0 0 50Potassium – magnesium sulfate 0 0 22Blends (N, P, K) 10 10 10 12 12 12 27 3 3 6 12 12 18 6 12___________________________________________________________________________________________________________
  • 38. Organic Fertilizers Organic Fertilizer %N % P2O5 % K2O ___________________________________________________________________________________________________________ Manure (fresh) bat 6.0 9.0 3.0 cattle 0.55 0.55 0.45 hog 0.50 0.35 0.45 horse 0.65 0.25 0.50 poultry 1.00 0.85 0.45 rabbit 2.4 1.4 0.6 sheep 0.9 0.5 0.8 Alfalfa hay 2.5 0.5 2.1 Bone meal (steamed) 1.0 15.0 0.0 Fish scraps 9.0 7.0 0.0 Lawn clippings 1.2 0.3 2.0 Leaves (sugar maple) 0.7 0.1 0.8 Milorganite * 5.0 3.0 2.0 Straw (wheat) 0.6 0.2 1.0 Grain straw 0.6 0.2 2.1 Sawdust 0.2 0.1 0.2 Wood ashes 0.0 2.0 6.0 ___________________________________________________________________________________________________________ * Not acceptable for organic fruit and vegetable production
  • 39. Value of Soil Testing
  • 40. Sweet Corn Tissue AnalysisElement Conc. Interp. Element Conc. Interp. (%) (ppm) N 1.72 Def. Fe 79 Suff. P 0.16 Def. Mn 860 Excess K 2.01 Low Cu 8 Suff. Ca 0.28 Def. Zn 22 Suff. Mg 0.15 Def. B 4 Low S 0.09 Def.
  • 41. Sweet Corn Soil TestpH P K Mg Ca S Zn Salts ------------------------ ppm ------------------- mmhos/cm3.8 96 90 16 106 3 0.8 0.2L H M L L L M L
  • 42. Aluminum Toxicity – low pHAl, Mn toxicity at pH <5 or 5.5 for many plants 43
  • 43. Recommendationl Lime to pH 6 in the fall with dolomitic limel Apply potassium-magnesium sulfate in the spring preplantl Soil test yearly to monitor changes
  • 44. Additional Informationl Nutrient Management for Commercial Fruit and Vegetable Crops in Minnesota BU-5886-E - 2005 University of Minnesota Extension Service q University of Minnesota Soil Testing Lab q q Phone: 612-625-3101