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Grow Your Own, Nevada! Fall 2012: Gardening in Nevada's Soils

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Grow Your Own, Nevada! Fall 2012: Gardening in Nevada's Soils

  1. 1. Gardening in Nevada’s Soils Mission Possible!
  2. 2. Gardening in Nevada’s Soils What is healthy soil? How does soil form? Soil has many components: – Textural or structural – Biological – Chemical How can you improve your soil?
  3. 3. Healthy soil has:  Good porosity  Good drainage  Good water-holding capacity  Good tilth, meaning they’re easy to work  Lots of organic matter  Lots of organisms  A pH of about 7 OSU Extension Service  Low salinity and sodium levels
  4. 4. How are soils formed? A. Miller
  5. 5. Nevada Soils Many challenges – Climate – Organisms – Parent material – Time – Topography
  6. 6.
  7. 7.
  8. 8.
  9. 9. It’s not your fault! You didn’t do anything wrong! We have very young soils geologically Their youth makes them: – Highly variable both vertically and horizontally – Low in organic matter – Still a work in progress
  10. 10. Compare horizons OSU Extension Service
  11. 11. What are soils made of? Minerals Air Water Organic matter (humus) USDA NRCS
  12. 12. “Ideal” composition of a soil Mineral Water = 20 to 30% Fraction (sand, silt, clay) = 45 to 50% Air = 20 to 30% Organic Matter = 0 to 5%
  13. 13. Soil minerals textural classes A. Miller
  14. 14. The dreaded soil textural triangle! A. Miller
  15. 15. Textural triangle for the graphically challenged NRCS, Bozeman Mont.
  16. 16. Why determine soil texture? Soil texture influences: Ease of tillage Amount of pore space or porosity Water infiltration rates Water-holding capacity Soil fertility or nutrient-holding capacity
  17. 17.    Water spreads CLAY differently Wide, but more shallow, infiltration in SILT different Moderate spread and soil infiltration textures SAND Deepest penetration
  18. 18. Sand versus Clay Clay - “Heavy” soil - High water-holding capacity - Slow infiltration - High nutrient-holding capacity Sand - “Light” soil - Low water-holding capacity - Fast infiltration - Low nutrient-holding capacity
  19. 19. Soil texture affects drainage In this experiment, an equal amount of water was applied to three soil types. NRCS, Bozeman, Mont.
  20. 20. Soil texture affects drainage Note the amount of water that drained from the sandy loam soil. NRCS, Bozeman, Mont.
  21. 21. Soil texture affects drainage Less water has drained from the silty clay loam soil. NRCS, Bozeman, Mont.
  22. 22. Soil texture affects drainage The loam soil drained almost as much as the sandy loam. NRCS, Bozeman, Mont.
  23. 23. Soil texture and drainage A. Miller Infiltration rate, Soil texture inches per hour Sand 2-4 Sandy loam 1-3 Silt loam, loams 0.25 – 1.5 Silty clay loams, clay 0.1 – 0.3
  24. 24. Water Infiltration
  25. 25. Where do plants get their water from in the root zone? Adapted from PNW 475 by A. Miller
  26. 26. Soil texture Sandy soil watering tips Clay soil watering tips  Emitters close to the  Emitters further from plant the plant  Higher volume per  Lower volume per hour emitters hour emitters  Low duration  Higher duration  Increased frequency  Lower frequency
  27. 27. Texture by feel: Sand Adapted from NRCS, Bozeman Mont. by A. Miller
  28. 28. Texture by feel: Loamy sand Adapted from NRCS, Bozeman Mont. by A. Miller
  29. 29. Texture by feel: Loams and clays Adapted from NRCS, Bozeman Mont. by A. Miller
  30. 30. Can you change soil texture?  No, not really!  Add sand to clay – mess!  Add clay to sand – mess!  Texture may limit your plant choices  How can you improve your soil texture? – add organic matter!
  31. 31. Soil organic matter consists of: Living organisms Dead organisms Plant matter Other UNCE, Reno, Nev. decomposing organic materials
  32. 32. Benefits of soil organic matter Improved water infiltration Increased water- and nutrient- holding capacity Formation of soil into stable aggregates Reduced soil compaction
  33. 33. Nutrient-holding capacity
  34. 34. Water molecule
  35. 35. Nutrients held in the soil are available for plant growth
  36. 36. Soil Structure
  37. 37. Soil structure: How particles are grouped together into stable collections by organic matter “glue,” also called “peds” or soil aggregates Platy Granular structure structure
  38. 38. Composition of a compacted soil Before After 50% 70% Note the reduced air space in a compacted soil.
  39. 39. Soil Compaction
  40. 40. Soil compaction
  41. 41. Avoid walking or driving on wet soil Avoid working wet soil OSU Extension Service
  42. 42. The wetter the soil, the worse the compaction effect by mechanized equipment
  43. 43. Adding organic matter: Improves water infiltration Increases water- and nutrient-holding capacity Forms soil into stable aggregates Reduces soil compaction  Also – feeds soil biota!
  44. 44. The living soil USDA NRCS
  45. 45. worm USDA NRCS
  46. 46. Add organic matter to your soil What kind of organic matter? Composted or well-rotted OM OSU Extension Service
  47. 47. OSU Extension Service What about manure? Uncomposted manure can be high in salts (burns plants and seeds) and can contain weed seeds, diseases, and insect eggs and larva.
  48. 48. Erosion Control Another method to manage soil Soil takes time to form – you don’t want to lose it! Keep a cover on the soil – plants, mulch, etc. Provide for drainage paths and armor them to reduce the potential for erosion
  49. 49. Protect slopes
  50. 50. Redirect the rain
  51. 51. Check irrigation often
  52. 52. Chemical Properties of Soil pH – potential of Hydrogen EC – Electrical Conductivity Nutrient content (plant nutrients)
  53. 53. pH Indicates relative acidity or alkalinity pH 7 = neutral; less than pH 7 = acid; more than pH 7 = alkaline or basic Adapted from by A. Miller
  54. 54. pH – Potential of Hydrogen Measure of the amount of hydrogen Negative logarithm of hydrogen ion activity - 1 pH point is a ten-fold change pH of 7 = 1.0 x 10-7 hydrogen ions equal H+ and OH- ions pH of 3 = 1.0 x 10-3 Hydrogen ions more H+ than OH- acidic pH of 10 = 1.0 x 10-10 Hydrogen ions more OH- than H+ alkaline or basic
  55. 55. Soil pH and nutrients Adapted from by A. Miller Widest part of the bar indicates maximum availability
  56. 56. Can I change my soil pH? Not really – our soils are alkaline Limestone (calcium carbonate) buffers our soils  CaCO3 + 2HCl = 2Cl- + Ca+2 + H2O + CO2 (gas) Can add sulfur, but takes time to lower pH and change is not always not permanent
  57. 57. EC or Electrical Conductivity Measures how well soil conducts an electric current Salts that dissolve in water conduct electricity Plants need some “salts” – these are nutrients Very high EC = high salt content If salt contents are high, it can interfere with plant growth
  58. 58. Classifying salt-affected soils Electrical conductivity measurements (EC) Exchangeable sodium percentage (ESP) Salt-affected soils are commonly classified for management purposes into three groups: saline, sodic, and saline-sodic based on EC and ESP
  59. 59. What to do about salt-affected soil? If you have tested and find you have salt- affected soil: – Flush the soil with water to wash the salt down below the growing zone Problem: – High water tables, poorly drained soil and high salt content irrigation water are often the cause of or contribute to high salinity
  60. 60. Managing salt-affected soils Select plants that can tolerate salinity Avoid excess or salty forms of fertilizers Incorporate organic matter If appropriate, add sulfur to lower the pH If a serious problem, go to raised beds with good drainage
  61. 61. Plant nutrients Substances necessary for plant growth Plants make their own food – these are the vitamins and minerals plants need to make their food and to grow Excess or improper use of fertilizers may result in plant damage and water pollution Split into two groups, based on the amount of the nutrients the plants need to survive and thrive
  62. 62. Macronutrients N = nitrogen C = carbon P = phosphorus Ca = calcium K = potassium Mg = magnesium H = hydrogen S = sulfur O = oxygen
  63. 63. Micronutrients Fe = iron Ni = nickel Mn = manganese Cu = copper Zn = zinc Co = cobalt B = boron Cl = chlorine Mo = molybdenum
  64. 64. What do the nutrients do?
  65. 65. Carbon, Hydrogen, Oxygen Building block of organic molecules From the air and water Generally not deficient (we’d be in trouble too!) These things cycle, just like the water cycle
  66. 66. Nitrogen, N  Constituent of amino acids, which are building blocks of proteins and enzymes.  Also component of nucleic acid and chlorophyll  Generally, this is the limiting factor or nutrient in plant growth.  Complex cycle, since it is a big constituent of all life on the planet - atmosphere is 78% nitrogen gas or N2
  67. 67. Nitrogen, N Deficiency symptoms: – Slow growth, stunting, chlorosis (yellowing) – Begins with older tissues; nitrogen is mobile and moves to younger tissues (N mobile) Excess N symptoms – Excessive vegetative growth – dark green – Delayed maturity, few fruit
  68. 68. Visual symptoms of deficiencies: Nitrogen
  69. 69. Phosphorus, P or P2O5  Most important plant function is the storage and transfer of energy (ADP and ATP (adenosine di- and triphosphates))  Also component of DNA and plays a critical role in cell membranes  Absorbed by plant roots form the soil as the ion H2PO4-1 and HPO4-2  Does not really move much in soil, just changes form, which may make it unavailable to plants – BUT will move with the soil – prevent erosion
  70. 70. Phosphorus, P or P2O5  Deficiency symptoms: – Slow growth, stunting, purplish or dark green color on foliage – Interveinal chlorosis (leaves are yellow on the upper surface, but remain green at the base) – Delayed maturity, poor fruit or seed development – Does move in plants, so deficiency symptoms show in the older leaves  Excessive P symptoms: – Can interfere with micronutrient absorption
  71. 71. Visual symptoms of deficiencies: Phosphorus
  72. 72. Phosphorus deficiency
  73. 73. Potassium, K  Important in many plant function, such as carbohydrate metabolism, enzyme activation, and protein synthesis  Essential for photosynthesis, starch formation and N fixation in legumes.  As a result of these functions, a good supply of potassium produces plump grains and large tubers or roots  Exists as ion (K+) in plants  Helps plants adapt to environmental stresses
  74. 74. Potassium, K Deficiency symptoms: – Slow growth – Leaf tip and marginal burn and necrosis on older leaves – Mobile in plants, so older leaves show the deficiency symptoms – Weak stalks, small fruit, shriveled seeds Excessive K symptoms: – Light green foliage, can look like Ca and Mg deficiency
  75. 75. Visual symptoms of deficiencies: Potassium Corn Alfalfa
  76. 76. Sulfur: Essential for production of proteins, enzymes and vitamins Helps in chlorophyll formation Improves root growth and seed production Helps with vigorous plant growth and resistance to cold
  77. 77. Sulfur: Deficiency symptoms: – Yellowing on new leaves first, starting at tip of leaf; older leaves stay green – Sulfur is not mobile in plants, so new growth shows the deficiency symptoms – Stunted growth Excess sulfur generally not a problem
  78. 78. Sulfur deficiency
  79. 79. Calcium, Ca Essential component of plant cell walls and membranes Regulates cell permeability and cell integrity We have adequate Ca in our soils
  80. 80. Calcium, Ca Deficiency symptoms: – Reduced terminal growth of shoots and roots – Symptoms show in new growth first – Ca+2 is not mobile in plants. Excess Ca+2 symptoms – Interferes with other nutrint uptake – Increases soil pH
  81. 81. Calcium deficiency
  82. 82. Magnesium, Mg Part of chlorophyll molecule and many enzymes Aids in mobility and efficiency of phosphorus
  83. 83. Magnesium, Mg Deficiency symptoms: – Interveinal chlorosis (leaves are yellow on the upper surface, but remain green at the base) or marginal yellowing with mid rib remaining green (tree pattern) – Marginal necrosis – Mobile in plants, so older leaves will show symptoms first (it moves to younger leaves) Excess Mg symptoms – Interferes with Calcium uptake
  84. 84. Mg deficiency
  85. 85. Micronutrients Required in very small amounts Essential components in enzymes, chlorophyll, DNA, etc Deficiencies are rare – generally it is the macronutrients that cause the observed problems Iron and zinc deficiencies are most common problem in our area
  86. 86. Iron, Fe Interveinal chlorosis (veins remain green) and reduced growth Common in our soils due to pH – iron is there, but not in a form plants can readily use Not mobile in plants, so symptoms on young leaves Certain plants more susceptible
  87. 87. Visual symptoms of Fe deficiency
  88. 88. Manganese, Mn Interveinal and marginal chlorosis, but no green vein areas, as with Fe Excess leads to Fe deficiency Not mobile in plants, so effects show first on young leaves Essential in vitamin C production, citrus plants require foliar spray of Mn and Zn
  89. 89. Visual symptoms of deficiencies: Manganese
  90. 90. Zinc, Zn Interveinal chlorosis, decrease in stem length, rosetting of terminal leaves Not mobile, so young leaves and other terminal growth areas are affected first Common deficiency in many crops Excess Zn symptoms?
  91. 91. Visual symptoms of deficiencies: Zinc
  92. 92. Boron, B Not remobilized in plants, so affects new growth first and can cause death of terminal growth areas or malformed, cupped leaves Rare deficiency – we more commonly worry about excess B! Excess can cause marginal necrosis Generally, excess means soil has other problems, like salinity issues
  93. 93. Boron deficiency
  94. 94. Boron toxicity
  95. 95. Copper, Cu Deficiency symptoms are stunted growth, poor pigmentation and death of leaf tips Affects new growth CAUTION! Always test if you suspect Cu deficiency – Cu can be highly toxic. Excess can cause reduced growth and necrosis
  96. 96. Chlorine, Cl Rare deficiency Excess can cause poor growth and marginal necrosis
  97. 97. Molybdenum, Mo Deficiency similar to nitrogen – Mo plays key role in N use in plants Stunting, chlorosis, reduced yield Affects older leaves – like N, it is mobile in plants and moves to younger growth Excess symptoms?
  98. 98. And last, but not least Nickel, Ni Movement in soil poorly understood. Complex chemistry and forms many ions Deficiency forms leaf tip necrosis Excess interferes with Fe and Zn uptake, chlorosis symptoms
  99. 99. In general… Ca and B show symptoms on terminal buds Fe, Mn, S and Cu show symptoms on young leaves (not mobile in plants) N, P, K, Mg, Zn and Mo show symptoms on old leaves (mobile in plants, they will move to younger leaves)
  100. 100. How do we add nutrients? Minor amounts in compost Minor amounts in soil “amendments” Generally added as fertilizer
  101. 101. Types of fertilizers Chemical fertilizers Organic fertilizers or amendments (bone meal, compost, manure, etc.)
  102. 102. Complete vs incomplete fertilizer “Complete” fertilizers contains the top 3 nutrients, like 16-16-16 general fertilizer: – Nitrogen (N) – Phosphorus (P) – Potassium (K) – 4th number, if present, is Sulfur (S) “Incomplete” fertilizers do not contain the top 3 nutrients, like Ammonium Sulfate 21-0-0
  103. 103. WAY TO GROW FERTILIZER What’s in the bag? 28 – 14 - 5 GUARANTEED ANALYSIS Product name Total nitrogen 28% NPK formula 6% Ammonium nitrogen 14% Urea nitrogen Nitrogen content Available phosphoric acid 14% Phosphorus content Soluble potash 5% Potassium content Specific sources Derived from sulfur-coated urea, etc.
  104. 104. A word about gypsum Gypsum is CaSO4.H2O Good source of Calcium and Sulfur Good for Sodium-Affected Soils NOT a panacea for clay soils! Too much Ca can interfere with chemical balance in soil and can contribute to a magnesium deficiency and interfere with other micronutrient availability
  105. 105. How do I know what to add to my soil??? Test your A. Miller soil!
  106. 106. What should I test for? What information does a normal soil test provide? Soil textural analysis pH and salts Soil nutrient content Fertilizer recommendations Call your local extension office for a list of soil testing labs
  107. 107. Call the Lab FIRST! Find out what they test for Find out if they have package deals Find out how much sample they want you to take Find out how they want the sample delivered to them Call UNCE 784-4848 for list of labs
  108. 108. How to take a sample First, select the site. Your soil sample should represent only one soil type or soil condition. OSU Extension Service
  109. 109. How to take a sample Each sample should consist of sub-samples taken from about 5-15 locations within the same soil type or sampling area. OSU Extension Service
  110. 110. How to take a sample Use the “slice” method for a representative sample. UNCE, Reno, Nev.
  111. 111. How can I manage my soils to improve them? Increase the organic matter content by: • Adding compost and well-rotted manure Avoid compaction by: • Reducing tillage of wet soils • Reducing traffic on wet soils • Establish paths Maintain cover with vegetation or mulch to reduce potential for erosion Fertilize when needed

Editor's Notes

  • Soils Melody Hefner 02/25/13
  • Slide of 67 Good soil structure is very important to the functioning of your small-acreage property. Many on-farm activities can destroy soil structure over time, including tilling and plowing or driving on wet soils. A good quality soil has the characteristics listed on this slide. Most of these characteristics are also associated with good soil structure. 02/25/13 Melody Hefner Soils
  • Five major influences on soil formation include the nature of the original parent material, weathering time, climate, land surface features or topography, and the actions of plants and animals. These factors determine the physical and chemical properties of various kinds of soil. Compare a soil that formed on steep slopes over 10,000 years in a rainy climate, where trees dominate and the parent material is granite, with one that formed in the last 2,000 years in a valley near a river in a cold climate, where grasses dominate and the parent material is limestone. 02/25/13 Melody Hefner Soils
  • 02/25/13 Melody Hefner Soils
  • Soils Melody Hefner 02/25/13
  • Slide of 67 The differences in soil layers affect such things as drainage, water holding capacity, root penetration, and tilth. The soil on the left has very distinctive color changes from horizon to horizon. Over time, iron leached from the horizons above to the horizons below, changing the appearance. The slide on the right shows changes in the size of particles with depth. Notice the increase in numbers of cobbles (small rocks) in the deeper horizons. The cobbles probably increase the drainage capacity of the soil while lowering its water holding capacity. 02/25/13 Melody Hefner Soils
  • Soils are composed of mineral material and organic matter, and contain pore spaces filled with water or air and soluble nutrients. Organic matter serves as a binder for mineral particles, contributing to good soil structure and tilth, which refers to the behavior of soil under cultivation. Minerals comprise the largest part of the soil, and organic matter is usually the smallest portion of the soil. Most people don’t think about the presence of air in the soil, and yet it is essential for plant growth and soil biology. 02/25/13 Melody Hefner Soils
  • Slide of 65 Atypical “loam” soil is composed of about 45 to 50 percent pore space. This pore space volume can be as little as 30 percent in a sandy soil and as much as 50 percent in clay soils. Pore space determines the amount of water potentially available to plants. Instructor: Ask the students, “Which weighs more, a bucket of dry sand, or a bucket of dry clay?” The answer is sand, due to its increased density (mass per unit volume). However, students will usually guess clay, opening the door for fruitful discussion. 02/25/13 Melody Hefner Soils
  • The mineral fraction of the soil refers to the primary minerals that make up the sand, silts and clays. Sand, silt and clay particles give the soil its particular texture. Sand particles can be seen with the naked eye, while silt and clay particles are microscopic. Because of its platy structure, clay has enormous surface area. This surface area provides habitat for microorganisms and is the location of many chemical reactions in soils. One gram of fine colloidal clay can have between 10 square meters and 1000 square meters of surface area. 02/25/13 Melody Hefner Soils
  • You can make a rough determination of soil texture based on the way it feels in your hand. Texture refers to the relative proportions of sand, silt and clay in the soil. The textural triangle is used to organize soils based on their textural class according to the varying percentages of sand, silt and clay. Sandy soils feel gritty to the touch. Silt soils will feel very slippery or viscous when very wet, like baby powder. Clay soil is sticky when moist, and can form a long ribbon when molded in the hand. The ideal soil for agriculture, as can be seen in this chart at the center of the triangle, is a loam soil. These soils have high water holding capacity as well as good “workability” and drainage properties. The blue area in the circle marked “loam” represents the most desirable soil texture type. The outer green circle represents those soil texture types that are acceptable or amendable. The remainder of the triangle, colored brown, represents those soil textures that are least desirable. 02/25/13 Melody Hefner Soils
  • Notice that loam soils have moderate amounts of all three textural classes. 02/25/13 Melody Hefner Soils
  • You may be wondering why we’re talking about soil texture. While this is a property of the soil that you cannot change, by knowing your soil texture you can make predictions about how it will behave. For example, a coarse sandy soil is easy to till, has plenty of aeration for good root growth, and is easily wetted, but it also dries out rapidly and loses plant nutrients as water drains away. High clay content soils (more than 27 percent clay) have very small particles that fit tightly together, leaving little open pore space. This means that there is little room for water to flow into the soil, making clayey soils difficult to wet, difficult to drain, and difficult to till. Anyone who has tried to hack through a hardpan area is all too familiar with this! 02/25/13 Melody Hefner Soils
  • Slide of 65 Water infiltrates differently in soils with different textures. Water spreads more widely in a clay soil because of higher water tension compared to sandy soils. You’ll also note that the depth to which the soil has wetted is greater in the sandy soil due to lower water-holding capacity. In soil with 50 percent available water content, if you apply an inch of water, in a sandy soil the water will move downward 40 inches; in a fine sandy loam, 24 inches; and in a loam soil, only 12 inches. This slide also provides a good demonstration of what can occur when a drip system is used. The placement of the drip line relative to the plant is an important consideration, especially in sandy soils. 02/25/13 Melody Hefner Soils
  • Instructor: This is a great demonstration you can use in the classroom. In lieu of a wooden stand, use clear one-liter soda bottles. Cut the bottles in half, and turn the spout end upside down. Place soil in the bottom half of the spout section. Use some old nylon netting to cover the spout so the soil doesn’t fall through. Try to use very different soil textures. Use equal amounts of soil (measure with a plastic cup). Add equal amounts of water and see how quickly they drain, and how much water drains through. If you begin this demonstration early in the class, you can revisit it at the break. 02/25/13 Melody Hefner Soils
  • Slide of 67 Sandy soils drain rapidly and don’t hold water well. 02/25/13 Melody Hefner Soils
  • Slide of 67 Clay soils drain slowly and have a high water-holding capacity. Note that the water is clearer with less suspended material. 02/25/13 Melody Hefner Soils
  • Slide of 67 Loam soils have good drainage but also have good water holding capacity - something to strive for in your soil. The organic matter from the loam soil leached through as the water slowly passed from top to bottom, providing a brownish color. Instructor: Be aware that this type of leaching demonstration can contradict theory of drainage because the soil structure was disrupted when creating the tubes. Therefore, you could end up with a silty clay loam that drains better than a sandy loam. Try the experiment before you use it with your students. 02/25/13 Melody Hefner Soils
  • Different soil types transmit water differently. Sandy soils allow water to infiltrate rapidly, but water also drains easily from the large pores. Infiltration rates for clay soils can be quite slow, and the runoff potential is high. But, the water holding-capacity is large due to the finer pore space. 02/25/13 Melody Hefner Soils
  • Slide of 65 When considering which plants to grow, remember that most moisture is extracted by the plant roots present in the upper half of the rooting zone. In this idealized graphic, 40 percent of extraction occurs in the top one-quarter of the root zone, 30 percent in the next quarter, and only 30 percent in the lower half of the rooting zone. The upper rooting zone is the area where the soil will tend to dry out fastest, and where most nutrients are extracted. It’s important to manage irrigation water to keep it within the effective rooting zone. Water that moves below this root zone becomes unavailable to the crop, is effectively “wasted,” and can leach nutrients into groundwater. Every plant is different in its rooting habits, of course, and restrictive soil layers may affect rooting depths. Photo source: Adapted by A. Miller, Black Dog Graphics, from Soil Water Monitoring and Measurement. PNW 475. A Pacific Northwest Publication. Washington, Oregon and Idaho. Thomas Ley et al. 02/25/13 Melody Hefner Soils
  • The next three slides demonstrate an indoor soil texture exercise. In this exercise, we will determine texture by feel. We will go through an example first and then working individually, you can determine the texture of several samples found at the back of the room. Instructor: The next three slides demonstrate an indoor texturing exercise you can use with your students. Materials needed: Three or more different soils from the local area in buckets Several squirt bottles filled with water Newspapers or drop cloths to prevent messes Paper towels Handout of the flow chart Have students determine the texture of at least two different types of soil. 02/25/13 Melody Hefner Soils
  • Slide of 67 02/25/13 Melody Hefner Soils
  • Slide of 67 02/25/13 Melody Hefner Soils
  • Slide of 67 Soil organic matter has several parts: The living microbes in the soil such as bacteria and fungi, which break down very rapidly when they die. Partially decayed plant material and microbes, such as plant material or manure (either deliberately mixed in or naturally occurring). The stable material formed from decomposed plants and microbes. This material is called humus, and is broken down very slowly. Organic matter affects both chemical and physical properties of the soil. 02/25/13 Melody Hefner Soils
  • Slide of 67 The benefits of a soil rich in organic matter and humus are many, and include: Chemical effects: Organic matter releases many plant nutrients as it is broken down in the soil, including nitrogen (N), phosphorus (P) and sulfur (S). It is also one of two sources of cation exchange capacity (CEC) in the soil. (Clay is the other major source.) CEC represents the sites in the soil that can hold positively charged nutrients like calcium (Ca++), magnesium (Mg+) and potassium (K+). If CEC is increased, the soil can hold more nutrients and release them for plant growth. To increase CEC, you have to increase organic matter. Physical effects: Organic matter loosens the soil, which increases the amount of pore space. This has several important effects. The soil becomes less dense (less compacted) and the soil structure improves. This means that the sand, silt and clay particles in the soil stick together, forming aggregates or crumbs. Because there is more pore space, the soil is able to hold more water and more air. Plants grown in healthy soils won’t be as stressed by drought or excess water. Water also flows into the soil from the surface more quickly. With less compaction, it is also easier for plant roots to grow through the soil. 02/25/13 Melody Hefner Soils
  • CEC is the capacity of the soil to attract and bond with positively charged nutrients. Clay and humus are the only particles in the soil that can attract and bond with the nutrients. That is because they are negatively charged. If the CEC in soil is low then these nutrients will go into solution and be washed away with water or irrigation. 02/25/13 Melody Hefner Soils
  • Slide of 67 Soil particles and organic matter are often found together in natural soil structures called soil peds, or aggregates. Cycles of wetting and drying and freezing and thawing promote ped formation. For this reason farmers often leave their fields exposed in winter to mellow the soil, but this practice can lead to compaction and erosion if no residue is left on the field. A well-developed soil structure enhances water and air movement and root growth. Soil structure is classified by the shape and size of soil peds. Granular structure is common under sod and refers to small balls of soil that easily separate. Soils with granular structure have larger pore spaces. Blocky structure is common in older clay soils in humid regions. Well-developed prisms and columns can be found in some clayey subsoils. Mud pie example: What happens to soil structure when you make a mud pie? Does that mud pie have the same physical characteristics as that of the original soil it was taken from? If you let the mud pie dry out, will it absorb water poured on it rapidly or slowly? Instructor: The specific categories of soil structure, referred to by soil scientists, are not mentioned here except to describe the photos in the slide. 02/25/13 Melody Hefner Soils
  • Slide of 67 In a compacted soil, the air space may be reduced to as little as 5 percent, reducing the ability of the soil to support plant growth. 02/25/13 Melody Hefner Soils
  • Slide of 67 Compaction reduces pore space and destroys soil structure. This site will not be good for growing anything unless it is treated with deep tillage and organic matter. Similarly, rototilling or plowing wet soil can lead to long term compaction problems. 02/25/13 Melody Hefner Soils
  • Slide of 67 The organic soil component includes all of the living creatures in the soil, as well as dead ones in various stages of decomposition. One cubic yard of live soil can contain as many as a billion colonies of bacteria, one hundred million fungi, one hundred thousand algae, billions of protozoa, thousands of mites, nematodes, collembola and earthworms. Without this fraction, the soil loses its ability to support plants and recycle nutrients. 02/25/13 Melody Hefner Soils
  • Soil organisms are the key to the soil food web and maintaining the soil ecosystem. Worms play a major role in recycling soil nutrients by burrowing tunnels and processing soils through their digestive tracts. They leave behind nutrient-rich worm castings. They not only release nutrients to the soil, but also aerate the soil with their burrows. Microorganisms such as bacteria, fungi and actinomycetes decompose organic matter and cycle nutrients in the soil to make them available to plants. Overuse of fertilizers and excessive disturbance or tilling of the soil reduces the number of organisms living in the soil. 02/25/13 Melody Hefner Soils
  • Slide of 67 Scientific studies and observation have shown that by preserving soil organic matter, soils function better. Soil organic matter is a small proportion of the total composition of the soil, yet its role in improving soil health and soil quality is enormous. Adding organic matter to parcels around freshly built homes is gaining in popularity because of water quality concerns. Organic matter will increase water infiltration in this soil. Without the addition of organic matter, this soil will shed water much as the road does. 02/25/13 Melody Hefner Soils
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  • The pH scale ranges from 0 to 14. It measures the acidity or alkalinity of a solution. A pH of 7 means it is a neutral solution. Pure water has a pH of 7. A pH of less than 7 means the solution is acidic. A pH of more than 7 means the solution is basic, also called alkaline. The lower the pH, the more acidic the solution is. The higher the pH, the more basic the solution is. Each change of number in either direction represents a tenfold change in acidity or alkalinity. Most soils lie in the range of pH 5.5 to 8.5. Item pH Most acid soils 4.0 - 6.0 Lemon juice 2.2 - 2.4 Orange juice 3.4 - 4.0 Vinegar 4.0 - 4.5 Acid rain 3.0 - 5.0 Clean rain water 5.5 - 5.7 Fresh milk 6.3 - 6.6 Blood plasma 7.2 - 7.4 Mild soap solution 8.5 - 10.0 Instructor: Use indicator paper to measure the pH of some common substances, such as tap water, lemon juice, soda, etc. 02/25/13 Melody Hefner Soils
  • Soil pH affects the availability of plant nutrients as well as the biological activity of soils. Most essential plant nutrients are available at or around a neutral pH of about 7. As soils become more acidic (< pH 7) or alkaline (> pH 7), nutrients become less available. Also, bacteria tend not to do well in more acidic environments. Phosphorus is never readily soluble in the soil but is most available in soil with a pH range centered around 6.5. Extremely acidic soils (pH 4.0 - 5.0) can have high concentrations of soluble aluminum, iron and manganese that may be toxic to the growth of some plants. A pH range of approximately 6 to 7 promotes the best nutrient availability. 02/25/13 Melody Hefner Soils
  • Soil testing laboratories will report the salinity (conductivity) of soil in millimhos/cm (mmhos) or millisiemens/cm (mS). These two terms (mmhos and mS) are identical. The salinity of irrigation water is typically reported in micromhos (umhos) or microsiemens (uS). Conductivity is defined as the ability of a solution to conduct an electrical current, or the reciprocal of the solution's ability to resist the current. This current is conducted by electrically charged particles called ions, which are present in almost all solutions. Different solutions have different kinds and amounts of ions: distilled water has very few ions, and therefore a low conductivity, while sea water has a large number of ions, and a high conductivity. The greater the conductivity of the solution, the higher the reading. Salt affected soils are commonly classified for management purposes into three groups: saline, sodic, and saline-sodic. Two criteria are used for this classification, the electrical conductivity of the soil saturation extract (EC) and the exchangeable sodium percentage (ESP). Electrical conductivity is directly related to soluble salt concentration in soils. The exchangeable sodium percentage is a measure of the amount of sodium on soil exchange sites. 02/25/13 Melody Hefner Soils
  • Slide of 67 Managing these soils for growing crops can be difficult. In some cases, leaching with excess irrigation water to get rid of excess salts may be needed. If irrigation water is of low quality, the quantity of water applied should continually exceed the plant’s needs by 15 to 20 percent to provide enough water to maintain the root zone at safe salt levels. Make frequent, low volume irrigations to avoid plant stress. 02/25/13 Melody Hefner Soils
  • All plants, including crops, require many nutrients for proper growth and development. Macronutrients are nutrients needed in large quantities. Micronutrients are those needed in small quantities. Crops get carbon, hydrogen, and oxygen from air and water. The other nutrients come from the soil. To get economic crop yields, farmers must often add extra nitrogen, phosphorus, and potassium (beyond what exists naturally in the soil) in the form of commercial fertilizers and manure. The portion of these chemicals that is not used by crops may leach through the soil profile and into groundwater supplies used for drinking water. Phosphorus and potassium are not toxic, but nitrate levels in groundwater can reach toxic levels when certain soil types, weather conditions, and agricultural practices prevail. For this reason, it is important to use the results of your soil test to determine the nutrient needs of your soil and plants. 02/25/13 Melody Hefner Soils
  • The nine main nutrients are called macronutrients. These substances (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, carbon, hydrogen, and oxygen) are required in relatively large amounts. Nitrogen (N) is the plant nutrient most universally deficient for high crop yields. Nitrogen is the key ingredient for grass leaf growth. Be cautious in using nitrogen fertilizers. Nitrates are completely soluble in water and are easily washed away or leached below the plant’s root zone by over-irrigation, especially in sandy soils. This pollutes groundwater supplies and can result in unacceptable drinking water quality. Phosphorus is important for developing strong root systems, and for flowering and fruiting. In general, phosphorus does not leach through soils because it is tightly bound to soil particles and chemically reacts with other elements to form insoluble soil compounds. It can be lost via soil erosion. Potassium is necessary for durability and disease resistance. It seldom causes water quality problems because it is not hazardous in drinking water and is not a limiting nutrient for growth of aquatic plants. It is usually very abundant in the soil in western states. Like phosphorus, it is tightly held by soil particles, and can be lost by erosion. Previously, we mentioned that carbon, hydrogen, and oxygen were absorbed by plants from the air and water. The remaining three macronutrients are calcium, magnesium, and sulfur. Calcium is an essential part in all cell walls and membranes, and must be present for the formation of new cells. Young tissue is affected first in calcium-deficient soils. In alkaline soils where calcium availability can be quite low, supplemental calcium may be needed to adequately supply the plants. Sulfur is a constituent of three amino acids and is essential for protein synthesis and nodule formation on legume roots. The characteristic odors of plants such as garlic and onion can be traced to sulfur present in oil compounds. Sulfur deficiencies occur in a wide range of soil and climate conditions, and may result in retarded growth rates and delayed maturity. Magnesium is essential for photosynthesis and serves as an activator for many plant enzymes required in growth processes. While it is generally prevalent in western soils, it is more often deficient than calcium, especially in sandy soils. Yellowing of older leaves is a common sign of magnesium deficiency. 02/25/13 Melody Hefner Soils
  • The nine micronutrients (iron, manganese, zinc, boron, molybdenum, nickel, copper, cobalt, and chlorine) are required in tiny amounts. Except for chlorine, the primary role of the micronutrients is as activators in numerous enzyme systems. You will need to specially request micronutrient analysis, and it will increase the cost of the soil test. An adjustment in soil pH usually corrects deficiencies of the micronutrients. Each of these elements has a specific role in plant growth. A deficiency or an excess of any one will impair plant growth until the problem is corrected. Watching plant growth, testing the soil, and analyzing the plant tissue are ways to assess nutrient needs. Iron and manganese are the micronutrients most often deficient in landscape plants. Iron is most likely to be deficient in wet, clayey, or over limed soils. Manganese is more likely to be deficient in sands, calcareous soils, or organic soils. An adjustment in soil pH usually corrects deficiencies of the micronutrients. 02/25/13 Melody Hefner Soils
  • Slide of 67 Nitrogen deficiency causes chlorosis (yellowing) of the older leaves. The process begins at the tip of the leaf and proceeds down the midrib. As the deficiency becomes more extreme, leaves higher and higher on the plant are affected. The rest of the plant is often light green.   Instructor: The following slides show some of the visual symptoms of nutrient deficiencies. Point out that corn is a grass, and symptoms will be similar for all grass plants. Other photographs are available at 02/25/13 Melody Hefner Soils
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  • Slide of 67 Phosphorus deficiency is characterized by dark green plants and purplish leaves. The purple color is due to anthocyanin. Phosphorus-deficient plants are typically "spindly." Because of the marked effect that P deficiency has on retarding overall growth, striking foliar symptoms that are evidence of deficiency in certain other nutrients, for example N and K, are seldom observed simultaneously. 02/25/13 Melody Hefner Soils
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  • Slide of 67 Potassium deficiency symptoms on alfalfa include white spots on the edges of lower, older leaves. Potassium deficiency results in chlorosis of the lower, older leaves that begins at the leaf tip and proceeds down the leaf margins. Older leaves may wilt and look scorched. As the severity of K deficiency increases, the symptoms proceed up the affected plants.   02/25/13 Melody Hefner Soils
  • Slide of 67 Manganese deficiency is shown by yellowing between the veins of the upper, new leaves. There may be a reduction in the size of plant parts, including leaves, shoots, and fruits, or dead spots or patches.   02/25/13 Melody Hefner Soils
  • Slide of 67 Zinc deficiency symptoms occur on the upper, new leaves and can be seen as either interveinal chlorosis (yellowing between the veins of the leaves) or a band of chlorotic (yellow) tissue between the leaf edge and the midrib. The symptoms begin at the leaf base and expand toward the leaf tip.   02/25/13 Melody Hefner Soils
  • Slide of 67 Organic fertilizers are made from materials derived from living things. Animal manures, compost, bone meal and blood meal are organic fertilizers. Chemical fertilizers are manufactured from non-living materials. Rock phosphate, for example, is a common source of phosphorus in chemical fertilizers. Mineral fertilizers are made from naturally occurring raw materials containing nutrients which normally have been transformed into a more plant-available form by industrial processing. Although the number of chemical processes used is relatively small, there is a wide variety of finished products. Organic fertilizers are not immediately available to plants. Before the plants can use them, they must be broken down by soil microorganisms into simpler, inorganic molecules and ions. In contrast, the nutrients in chemical fertilizers are already in inorganic form and can be immediately used by the plants. It is important to understand that there is no fundamental difference in nutritional quality between organic and inorganic fertilizers. It makes no difference to the beet root if the atoms of potassium it absorbs are from an organic fertilizer such as wood ash or an inorganic one such as muriate of potash. Although they are immediately available to plants, inorganic fertilizers have three main disadvantages. They are subject to leaching, which occurs when the fertilizers are washed by rain or irrigation water down below the level of the plant roots. Nitrogen is particularly susceptible to leaching. Heavy applications of chemical fertilizers can "burn" seedlings and young plants. This is actually a process of drying out, or desiccation, due to the presence of chemical salts within the commercial fertilizers. A third problem associated with the use of commercial fertilizers is that overly heavy applications can build up toxic concentrations of salts in the soil and create chemical imbalances. A listing of organic fertilizers nutrient content, release times and pros and cons of different organic fertilizers can be found on the Organic Fertilizers Information Sheet. 02/25/13 Melody Hefner Soils
  • A variety of fertilizers are available commercially. Some provide only a single nutrient, such as ammonium nitrate, or triple superphosphate. Others contain three macro-nutrients: nitrogen, phosphorus, and potassium (potash). Nitrogen is expressed on the elemental basis (N) and phosphate and potash are expressed as the oxides (P 2 O 5 and K 2 O) rather than elemental phosphorus (P) and potassium (K). A fertilizer grade of 28-14-5 means that a 100-pound bag of fertilizer contains 28 percent or 28 pounds of nitrogen, 14 percent or 14 pounds of phosphorus ( P 2 O 5 ) , and 5 percent or 5 pounds of potassium (K 2 O) . The remaining 53 percent consists of other ingredients that help in packaging and spreading. Some fertilizers contain only one major nutrient. An example is 33-0-0 (33 percent nitrogen, no phosphorus or potassium). If there is a fourth number, it represents the percentage of sulfur (S). Nitrogen fertilizers can be divided into two categories: those that are quickly available to plants, called soluble or quick release, and those that are slowly available to plants, called slow release. The quick release fertilizers are salts that are very soluble in water, including ammonium sulfate, ammonium nitrate, ammonium phosphate, and potassium nitrate. Quick release nitrogen is easily misused, resulting in waste, plant burn and water pollution. To avoid these problems, split the fertilization into two separate applications three to five weeks apart. Irrigate carefully to avoid deep leaching into water supplies and surface runoff to irrigation ditches, streams, rivers, and other water bodies. Slow release N sources include materials that dissolve very slowly in water, materials that have been coated to delay release (sulfur-coated urea), and the natural organic types mentioned above. Natural organic N sources such as manure must be broken down by microorganisms in the soil. The rate of release of N will depend on soil moisture and temperature. Slow release forms of N provide lower concentrations of nutrients over a longer period of time. This decreases the likelihood of plant burn and increases the probability that nutrients will be used by the intended plants rather than pollute streams and lakes. Instructor: Make sure participants understand the forms in which P and K are generally provided, and how to calculate actual amounts of P and K. 02/25/13 Melody Hefner Soils
  • Sulfur Essential plant food for production of protein. Promotes activity and development of enzymes and vitamins. Helps in chlorophyll formation. Improves root growth and seed production. Helps with vigorous plant growth and resistance to cold. Sulfur may be supplied to the soil from rainwater. It is also added in some fertilizers as an impurity, especially the lower grade fertilizers. The use of gypsum also increases soil sulfur levels.  Excess Calcuim Symptoms. As mentioned, a proper balance between the concentrations of potassium, calcium and magnesium ions is important. Too much calcium can result in either magnesium or potassium deficiency. 02/25/13 Melody Hefner Soils
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  • Slide of 67 Be sure the test that you request will provide you with the information you need. Nutrients are not the only factor in good crop production. Before sending samples, contact the laboratory first. They may have special requirements for packing etc. Contact your local extension office for a list of analytical laboratories that serve your area. The results of a soil test can be used to make a fertilizer recommendation for certain crops and pastures. Soil testing laboratories use different test methods that may influence results and sufficiency ranges. Because labs may use different methods of analyses, and different analyses are appropriate for different soil types, it is advisable to send a soil sample to a lab in the same region where the soil sample is taken. A lab in your region may be more likely to use procedures suited for your soil type, and they may have data correlating the results to plant responses on similar soils. 02/25/13 Melody Hefner Soils
  • Slide of 67 When taking a soil sample, choose areas of the field that have conditions in common, as shown in this slide. Avoid areas where you know fertilizer has been placed recently. Sample unusual areas, such as low spots, separately. If areas are very different, you will need to collect separate samples. Be sure to use clean equipment to avoid contamination. Call the lab you have selected to test your samples prior to actual sampling for their specific recommendations on sample handling. 02/25/13 Melody Hefner Soils
  • Slide of 67 The accuracy of the soil test is a reflection of the sample taken, so make sure you have a good sample! Start by selecting about 15 locations randomly. Avoid sampling near gravel, manure or compost, septic leach fields, brush piles, or under eaves. 02/25/13 Melody Hefner Soils
  • Slide of 67 Dig a hole 6 to12 inches deep. Slide your shovel or trowel down the side of the hole from top to bottom, removing a “slice” of soil. Place all of the subsamples together in a clean pail and mix them thoroughly. Remove pebbles and debris. Let the sample dry. When dry, place about 1 to 2 cups of soil in a zip top bag, label and date the bag, and send the sample to the lab. Keep the sample cool and out of the sun. The lab may have other shipping requirements, so check with them first. 02/25/13 Melody Hefner Soils
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