- -  AGRICULTURE CORE CURRICULUM - -


(CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE

 (CLF6350)  Unit Title: ELEMENTS NECESSARY FOR PLANT GROWTH

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 (CLF6355)  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: WESTERN FERTILIZER HANDBOOK (7th ed.). (1985). 
                      Danville, IL: Interstate Printers and Publishers.

        Evaluation: Quiz by instructor

TOPIC PRESENTATION: SOIL AMENDMENTS

A. For many centuries people have added various types of organic matter to
   maintain or improve the soil's physical properties and increase
   production.

   1. Inorganic soil amendments function as wedges that physically separate 
       soil particles.

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

   3. We will discuss the various organic and inorganic products used for 
       amending soils 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. Physical soil amendments improve soils primarily by improving: 

   1. water retention

   2. water permeability

   3. air movement, and (ideally)

   4. root penetration

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 are wood residues that 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 is a product that 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, K, and other nutrients. It is recommended when the cost of
       hauling and spreading can be justified it is recommended.
       Precautions must be taken when manures are used to avoid excessive 
       salt accumulation.

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

F. Inorganic soil amendments include the following materials:

   1. Perlite is an extremely light (in weight) material. It is naturally
       occurring glassy volcanic rock that is heated to produce bead-like 
       particles. It is inert and water insoluble.

   2. 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.

   3. Pumice is a 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 it is used 
       mostly in greenhouse propagation mixes.

   4. 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. 

   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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1/6/91 PJK/clh


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