1 / 27

Understanding Soil Chemistry

Understanding Soil Chemistry. Importance of Soil Fertility. Soil Fertility Ability of a soil to provide nutrients for plant growth Involves storage and availability of nutrients Vital to a productive soil Fertile soil is not necessarily a productive soil Why?

noel
Download Presentation

Understanding Soil Chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Understanding Soil Chemistry

  2. Importance of Soil Fertility • Soil Fertility • Ability of a soil to provide nutrients for plant growth • Involves storage and availability of nutrients • Vital to a productive soil • Fertile soil is not necessarily a productive soil • Why? • Poor Drainage, Insects, Drought, and other factors can limit production

  3. Importance of Soil Fertility • Existing plant-soil relationships affect soil productivity • External factors control plant growth • Air • Temperature • Light • Mechanical support • Nutrients • Water • Plants rely on soil to provide all these except light

  4. Importance of Soil Fertility • Water and air fill pore spaces in soil • Factors that affect water relationships also affect soil air • Nutrient availability is influenced by soil and water balance and temperature • Root growth is influenced by soil temperature as well as soil, water, and air

  5. Understanding Soil Chemistry Soil Productivity

  6. Role of organic Matter • What is organic matter? • Plant, animal, and microbial residues • Varying stages of decay • Adequate levels of O.M. benefit soil by: • Improving physical condition and tilth • Increases water infiltration • Decreases erosion loss • Supplies plant nutrients

  7. Role of organic Matter • Organic matter contains about 5% N • N is not immediately available • Decomposition must occur first • Fertilizer (inorganic) N is needed for non-legume plants • Organic matter also provides soil with a variety of other mineral elements that plants need to be healthy • Some include: phosphorus, magnesium, calcium, sulfur, and others

  8. Role of Soil Depth • Soil Depth • Depth of soil material favorable for plant root penetration • Plants need soil to be: • Deep • Well-drained • Correct texture • Correct structure • Deeper soils provide for more nutrient storage

  9. Role of Soil Depth • Roots can extend 3-6 feet or more when soil depth permits • Rooting depth is affected by • Physical barriers • Chemical barriers • High water tables • Hardpans, Shale beds, Gravely Layers and accumulations of salts are very hard to correct

  10. Role of surface Slope • Surface slope is part of what? • Topography • Determines the amount of runoff and erosion • Also determines: • Irrigation method • Drainage • Conservation practices • The steeper the land the more management is needed • More labor and equipment costs

  11. Role of surface Slope • At certain slopes, soil is no longer suitable for row crops. • What are some row crops? • Potential productivity is largely determined by ease of erosion along with percent of slope

  12. Role of Soil Organisms • Many different organisms live in the soil • Usually in the first foot of top soil • Depend on organic matter for food • Factors that affect the amount soil organisms: • Moisture • Temperature • Aeration • Nutrient supply • Soil pH • Crop that is being grown

  13. Role of Soil Organisms • Some of the microscopic organisms cause many favorable soil reactions • decay of plant and animal residues • speed nutrient cycling. • Other reactions can be injurious • development of organisms that cause plant and animal diseases

  14. Role of Nutrient Balance • Nutrient balance is a vital concept in soil fertility and crop production • Nitrogen is the first limiting nutrient in non-legumes • Without adequate amounts of the other nutrients, N cannot do its best • As Nitrogen fertilization raises yields, the crop demands more of the other nutrients

  15. Understanding Soil Chemistry Soil pH

  16. Soil pH • The measure of acidity or alkalinity of the soil • pH is determined by the concentration of hydrogen ions(H+) and hydroxyl ions(OH-) in the soil solution • Pure water has an equal number of H+ and OH-

  17. Soil ph • Another term for alkaline is basic • Acid = high in H+ • Basic = high in OH- • A soil with a pH of 6.0 has 10 times as much active H+ than neutral

  18. Soil ph • Plants will not thrive in soil that is too acid or too alkaline • The soil pH directly affects the availability of mineral nutrients • Example • Low pH: phosphates may be bound chemically in the soil so plants are unable to access them • Also means that nitrate production in the soil is reduced

  19. Soil PH • Several factors influence Soil pH • Organic matter • Parent material • Rainfall • leaching • Forest vs. grassland • Harvesting crops • Legumes • Soil depth • Fertilizer application • Flooding

  20. Soil ph • How to measure soil pH • Indicator dyes • pH meter • Which do you think is more accurate? • The meter • If our soil’s pH was too acidic what would we add to amend it? • Lime

  21. Lime requirement • Soil pH is not the determining factor on how much lime to add • What else do we need to consider? • Texture of soil • Amount of organic matter • The amount of clay and organic matter in a soil will determine the ability of a soil to resist pH change • More clay/organic matter = more pH buffering • The process is very complex • Example: Al and water

  22. Lime requirement • Lime requirement • Amount of Ag limestone needed to establish the desired pH range for the cropping system being used • Lime reduces soil acidity • Look at Al and water example • Uses Ca ion • Soil will become more and more acidic if a liming program is not followed • We do not apply lime to soils here in Northern Utah very often… Why?

  23. Lime Requirement • In the case of high pH • Lowering pH is not usually economical • These are generally high in salts • Find plants that tolerate high salt levels

  24. Cation Exchange Capacity • As soils form • Some particles are broken down into extremely small particles • Chemical weathering breaks them down until they cannot be seen with the naked eye • The smallest are called colloids • Colloids are responsible for chemical reactivity in soil • Each colloid has a negative(-) charge

  25. Cation Exchange Capacity • The neg. charge will attract positively(+) charged particles • What does that mean if they run into another negative? • Cations: Positive Charge • Anions: Negative Charge • Colloids act like a magnet and holds cations • Other cations can take their place • They are exchangeable

  26. Cation Exchange Capacity • Can a soil hold more cations than it has colloids? • no • We need to know our soil’s CEC • Higher CEC = more cations can be held • Depends on clay and organic matter • Lots of clay = higher CEC • More organic matter = higher CEC

  27. Cation Exchange Capacity • Leaching is reduced by higher CEC • Knowing our CEC will help determine how much fertilizer to apply and how often

More Related