PLSC 368: Chapter 3

    PROPAGATION FACILITY

Plant propagation requires controlled environment for:

1. Temperature
2. Light
3. Moisture
4. Gases (O2, CO2 )
5. Mineral nutrition (fertilizer)
6. Cleanliness
I. STRUCTURES

    A. Cold frames
            -semi controlled environment (passive system)
            -used mainly for hardening seedlings and rooted cuttings
            -also used for vernalizing herbaceous perennials

    B. Hotbeds
            -a small, low structure
            -bottom-heated (by electrical heating cables, hot water, steam pipes, manure decomposition)
            -used for seed gernimation, herbaceous cuttings
            -problems:  seedling damping-off (Pythium, Rhizoctonia)
                               temperature may not be completely controlled

    C. Greenhouses

            1) Types--Quonset, ridge and furow (gutter-connected), lean-to(attached)

            2) Heating
                a. Steam (centralized)- pipes (including fin-type), heat exchanger

                b. Hot water (central, local)- pipes (fin-type), even distribution of heat
                c. Fan-jet system (localized)
                d. Fuel - natural gas, heating oil, coal, wood, electrical, solar
                                    Cost:  $0.5- $1.50/ft2 . yr
                                    Colorado:  $0.55 (carnation)      $0.75 (rose)

            3) Cooling---Natural ventilation
                                 Pad and Fan system (evaporative cooling system)
 


            4) Automatic Controls
                a. temperature (heating, cooling)
                b. watering (timer)
                c. CO2 injection

            5) Glazing Materials (covers)
                a. glass ($1.00/sq. ft)
                b. plastic :
                        Flexible
                            -polyethylene film (poly 6mil) $0.15/ 2layer . sq ft
                            -polyvinylfluoride (PVF, Tedlar)--UV resistant
                            -polyvinylchloride (PVC film, popular in Japan)
                        Ridgid
                            -fiberglass (corrugated)--Tedlar coated (cumbstable)
                            -acrylic (plexiglass, exolite) --doulbe layer $3/sq. ft
                            -polycarbonate (polygal, Lexan)--- $0.75/sq ft

            6) Propagation Structures within Greenhouse
                a. 'Wardian' Case- covered bench or structure (spore gernination, grafts)
                b. Germination chamber- 'Sweat Chamber' (high humidity, temp, lowlight)
                            bedding plant seeds
                c. Mist house- cutting propagation (bottom heat)
                            low pressure mist, high pressure fog

II. GROWING MEDIA

    A. Requirements
                -water retention
                -good aeration
                -nutrient holding (CEC)
                -neutral pH
                -free of toxicity

    B. Amendments

            1) Soil--Heavy, requires sterilizaation, high CEC
            2) Sand--No CEC, inert, heavy
                            used for improving aeration
            3) Peatmoss--Sphagnum or hypnum peatmoss (~70% decomposed)
                                    usually low in pH, high CEC, high water holding capacity, provides some nutrients
            4) Vericulite--expanded mica mineral
                                    high water holding, good CEC, good buffering
            5) Perlite-- expanded volcanic silicaceous rock (1400° F, vacuum)
                                very light, inert, no CEC, no buffering
            6) Pumice--crushed volcanic rock (heavier than perlite)
                                similar properties as perlite--mainly used for nursery crops in CA
            7) Bark, wood shavings, sawdust
                               problem with phenolics, tannins
                               use after decomposition
            8) Rockwool --shredded, sheets, cubes
                                     no CEC, no buffering, inert

III. MIXTURES FOR CONTAINER GROWING

    A. Mixtures Containing Soil

            1) Heavy soil (clay or clay loam)
                           1 part soil
                           2 parts perlite or sand
                           2 parts peat
            2) Medium soil (silt loam)
                            1 part soil
                            1 part perlite or sand
                            1 part peat
            3) Light soil (sandy loam)
                            1 part soil
                            1 part peat

                                            For 1, 2, and 3-- Add Base fertilizers (per bushel)
                                            8oz. dolomite (Ca, Mg)
                                            10oz. Superphosphate (P, S)

    B. The U.C. Mixes (Nursery Crops)

            1)  Used mostly for nursery crops (woody)

                  No.        % sand     % peatmoss
                    A            100                     0
                    B              75                    25
                    C              50                    50   (most common)
                    D              25                    75
                    E                0                 100

                 Base Fertilizers

                     For mix C, use (per cubic yd)
                            4oz. potassium nitrate (KNO3)
                            4oz. potassium sulfate (K2SO4)
                            2.5oz single superphosphate
                            7.5lb. dolomite (CaCO3. MgCO3)
                            2.5lb. limestone (CaCO3)

    C. The Cornell Peat-Lite Mixes (soil-less mix)

            Soilless mix or peat-lite mix (most flower crops)

                                                                      Bushel/yd3
                                                    Peat          Perlite   Vermiculite    Bark
            Peat-lite Mix A                    11             --             11            --
            Peat-lite Mix B                    11             11             --            --
            Foliage Plant Mix                 11            5.5            5.5           --
           Epiphytic Mix (Orchid)        7.3            7.3            --            7.3
               Base fertilizers:  ground limestone, superphosphate, calcium or potassium nitrate,
                                        Iron sulfate, Fritted trace elements, wetting agent

                Most commercial mixes are based on cornell peat-lite mixes
                        Example:  Sunshine Mix #1  (with base fertilizers)--many crops
                                        Sunshine Mix #2  (no base fertilizers)
                                        Sunshine Mix #3  (base fertilizers)--bedding plant seed germination
                        Promix, Metromix, etc.

IV. PASTEURIZATION OF GROWING MEDIA

    A. Steam Sterilization
            -Moist heat
            -30 min at 180° F (82° C)
            -Kills pathogen, weed, seed
            -Ammonium toxicity in heavy soils
                      Ammonifying bacteria                    Nitrifying bacteria                      Nitrifying bacteria
                OM       Actinomycetes        > NH4+            Nitrosomonas          > NO2        Nitrobacter           >NO3-
                    Crop residue                                 Ammonium                                            Nitrite                                          Nitrate

                  Remedy- Allow less OM in soil before sterilizing
                                -Aeration before use

    B. Chemical Sterilization

            Chemicals------Chloropicrin (Tear gas)
                                     Methyl bromide (Restricted)
                                     Vapan
             Problems    Some plants are sensitive
                                   i.e. Dianthus to Methyl Bromide
                                        Long aeration time (~14 days)
 

V.   pH ADUSTMENTS

    A. To Lower pH
            -Sulfur powder
            -Aluminum sulfate
            -Iron sulfate
            -Also use acids
                Sulfuric acid
                Phosphoric acid
                Nitric acid

    B. To Raise pH
            -Lime (CaCO3)
            -Dolomite (CaCO3. MgCO3)