- -   AGRICULTURE CORE CURRICULUM  - -


(CLF7000)  Advanced Core Cluster:  PLANT AND SOIL SCIENCE

  (CLF7450)   Unit Title:  ELEMENTS NECESSARY FOR PLANT GROWTH

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  (CLF7455)   Topic:  SOIL AMENDMENTS         Time      Taught in Year(s) 
                                             1 hour          3 and 4  
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         Topic Objectives:  Upon completion of this lesson the student will 
         be able to:

         Learning Outcome #:

           (H-6)  -  Define "soil amendment" and list three inorganic and 
                     three organic soil amendments.

           (H-7)  -  Identify three ways soil amendments can improve soil.

         Special Materials and Equipment: Samples of soil amendments.

         References: Interstate Printers and Publishers, Inc.
                     WESTERN FERTILIZER HANDBOOK
                     Pages 225 to 240.

         Evaluation: Quiz by instructor

TOPIC PRESENTATION:  SOIL AMENDMENTS

A.  For many centuries man has added various types of organic matter to
    maintain or improve the soils physical properties and increase
    production.

    1.  Inorganic soil amendments have as their function to act as wedges 
        that physically separate soil particles.

    2.  Organic soil amendments are derived from living sources, primarily 
        plant and animal which separate the soil particles and increase 
        nutrient and water holding capacities.

    3.  We will discuss the various products used for amending soils; 
        organic and inorganic and how they can improve soil.

B.  By definition a physical soil amendment is any substance used for the 
    purpose of promoting plant growth or improving the quality of crops by 
    conditioning soils solely through physical means.

C.  These amendments primarily improve soils by improving:  

    1.  water retention,

    2.  water permeability, and 

    3.  air movement.

D.  When a soil is supplied with adequate levels of air, water, organic 
    matter, and nutrients, amending is unnecessary.

    1.  Such ideal soils are rare.

    2.  Generally, we can improve soil by the use of amendments.

    3.  It is difficult to amend a soil once an area has been planted, so 
        amending must be done prior to planting.

E.  Here is a description of the more common organic amendments. 

    1.  Peat is composed of plant residues that have accumulated and 
        undergone partial decomposition in water or wet areas such as swamps 
        and bogs.  Peats exhibit a wide range of moisture holding capacity, 
        organic content, and longevity.  Once dry, they are hard to wet.

    2.  Sawdust and shavings.  These wood residues are widely used in 
        amending turfgrass, landscape soils, and container soil mixes.  
        They provide good water infiltration and oxygen, but are only poor 
        to fair for water and nutrient holding characteristics.

    3.  Ground fir bark.  This product is low in nutrient holding capacity.  
        It provides good water and oxygen diffusion rates into the soil.
        It resists compaction and lasts up to five years.

    4.  Manure can add considerable amounts of organic matter as well as
        N, P, and K and other nutrients.  When cost of hauling and spreading 
        can be justified it is recommended.  Precautions must be taken when 
        they are used to avoid excessive salt accumulation.

    5.  Other organic amendments are rice hulls, composts, manures, and 
        sludges.

F.  Inorganic soil amendments include the following materials.

    1.  Calcined clay is a long lasting fired clay that resists compaction 
        well and promotes water infiltration and oxygen diffusion.  It makes 
        a good surface mulch.  Though expensive, this material can help 
        establish high value turfgrass and landscape plant materials. 

    2.  Pumice is a spongy, light, volcanic rock.  In soil it promotes good 
        water infiltration and oxygen diffusion rates and thus encourages a 
        deep, dense root system.  It is relatively costly so is used mostly 
        in greenhouse propagation mixes.

    3.  Vermiculite is a mica material that has been heated, thus causing it 
        to expand to many times its original size.  The final product is
        very lightweight and can hold water in amounts several times its own 
        weight.

    4.  Perlite is an extremely light (in weight) material.  It is a natural 
        bead-like occurring glassy volcanic rock which is heated to produce 
        like particles.  It is inert and water insoluble.

    5.  Sand is a low cost, long lasting amendment used in special mixes for 
        golf courses, bowling greens, and nursery production.  

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          ACTIVITY:  
                      
          1.  Set out samples of the various soil amendments and have
              students study and identify them.

          2.  Various experiments can be performed using the soil 
              amendments:

              a.  Weigh equal amounts (by weight) of soil amendments.
                  Add water, drain, and weigh again when wet. 
                  Calculate their water holding capacities. 

              b.  Use various mixtures of these amendments and relate
                  them to root growth, root length, and root depth of
                  cuttings or seedlings grown in them.  Some will 
                  perform better than others under a mist propagation
                  program.
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6/21/90 sg


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