- - AGRICULTURE CORE CURRICULUM - -

(CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE

 (CLF6450) Unit Title: IRRIGATION AND DRAINAGE

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 (CLF6452) Topic: DRAINAGE                  Time            Year(s)
                                              1 hour           3 / 4 
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         Topic Objectives: Upon completion of this lesson, the student
                            will be able to:

         Learning Outcome #:

           (H-1) - Define the terms irrigation and drainage.

           (H-2) - Explain the importance of good drainage in the
                     planting of ornamental plants.

         Special Materials and Equipment: 

         References: Hartmann, H. T., Flocker, W. J., & Kofranek, A. M. 
                       (1981). PLANT SCIENCE: GROWTH, DEVELOPMENT, AND 
                       UTILIZATION OF CULTIVATED PLANTS. Englewood
                       Cliffs, NJ: Prentice-Hall:
                     Hausenbuiller, R. L. (1972). SOIL SCIENCE:
                       PRINCIPLES AND PRACTICES. Dubuque, IA: Wm. C 
                       Brown Co.
                     Landphair, H. C., & Klatt, F., Jr. (1979). LANDSCAPE
                       ARCHITECTURE CONSTRUCTION. New York, Elsevier
                       Science Publishing Co.
                     Editors of Sunset Books & Sunset Magazines. (1984). 
                       LANDSCAPING ILLUSTRATED. Menlo Park, CA: Lane 
                       Publishing Co.

         Evaluation: Unit Exam

TOPIC PRESENTATION: DRAINAGE

REVIEW: Drainage is the removal of excess gravitational water from the
        soil by natural or artificial means.

A. Importance of Drainage: When we irrigate a landscape, we are
   putting extra water into the soil. We need to be concerned about what
   happens to that water. Adequate drainage must be provided to take it
   away. Structural integrity and plant health are the two major reasons 
   why drainage must be adequate.

   1. Buildings and other construction in the landscape can be severely 
       damaged if drainage if not properly provided for. 

       a. Water stagnating in the soil can cause the soil to lose
           structure and begin to slump, thus undermining the structure.

       b. Wood in contact with the soil will quickly deteriorate. This is 
           not usually the case with a building, but fences and other 
           landscape construction are sometimes at risk.

       c. Water stagnating near a building will start to smell bad as
           anaerobic processes evolve in the soil.

   2. Nearly all plants need good drainage to thrive.

       a. Plants must have adequate aeration for their roots to stay
           alive. Respiration in the roots requires fresh oxygen, which is
           excluded by water.

       b. Poor drainage will stunt plant growth and foster soil pathogens
           such as fungi.

       a. Properly drained soils warm earlier in the spring, stimulating
           plant growth. 

       c. Good drainage increases aerobic microbial activity, which
           benefits plants greatly. 

       d. Good drainage reduces the amount of phytotoxic substances 
           (soluble salts, methane gas, sulfides) in the soil.

B. There are two facets to providing for good drainage in a landscape 
   situation:

   1. The soil itself must drain adequately.

       a. Water must move down through soil at a rate which will allow
           plant roots the air they need.

       b. Fine clay soils lack the porosity to drain quickly enough for
           most plants.

       c. If soil drains poorly, either amending it with a coarse organic
           material or replacing it entirely is required.

       d. Another reason for poor drainage is a hardpan or an abrupt
           textural change in the soil profile. Drainage will improve if
           these are broken up by sub-soiling or ripping.

       e. More information on improving soil drainage can be found in
           Topic Plan (CLF6402) Horticultural Soils.

   2. Water must have somewhere to go after it seeps down through the 
       soil.

       a. In a landscape, the subsoil is often very shallow, and will hold
           little water. Also, flow of water is restricted by structure
           foundations and other elements in the landscape.

       b. Removing water by artificial means is therefore often necessary 
           in a landscape.

       c. A landscape is unlike an agricultural field where deep, open
           ditches can be used to remove drainage water. Drainage
           improvements must be enclosed and buried.

       d. Drainage pipes or "tiles" can be laid underground to improve
           drainage:

           1) A satisfactory layout for a large tile drainage system
               requires considerable planning and experience. Pipes are
               generally set 3'-5' underground, and spaced 20'-200' apart,
               depending on soil texture. (Finer textured soils demand
               shallow, closely-spaced pipe.)

           2) Pipe must be laid at a slight slope (0.5-1% is adequate) to
               carry water away. The drain pipe must eventually empty into
               a deep catch basin or storm drain.

           3) Tile systems involve the laying of tiles (short sections of 
               pipe made from fired clay or concrete) or continuous
               sections of perforated plastic pipe. 4" plastic pipe is
               the most common material used now for residential and small
               commercial landscapes. Large developments may use larger
               pipe sizes.

           4) Gravel or crushed rock is usually poured around the tile to
               prevent entrance of soil particles into the drain, and to
               facilitate the movement of water into the pipe.

           5) Landscape fabric can be used to enclose the drain to prevent
               siltation and clogging.

           6) This system interconnects and allows water to move
               underground and away from a landscape.



















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