- - AGRICULTURE CORE CURRICULUM - - (CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE (CLF6400) Unit Title: HORTICULTURAL SOILS & PLANTING MEDIA ____________________________________________________________________________ (CLF6404) Topic: SEEDBED PREPARATION Time Year(s) 1 hour 3 / 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the student will be able to: Learning Outcome #: (G-4) - Discuss the importance of proper seedbed preparation and identify four tools or pieces of equipment necessary for this task. (G-5) - Explain the effect of depth of planting on seedling emergence. Special Materials and Equipment: References: Cooper, Elmer L. (1990). AGRISCIENCE: FUNDAMENTALS AND APPLICATIONS Albany, NY: Delmar Publishers. Hartmann, H. T., Flocker, W. J., & Kofranek, A. M. (1981). PLANT SCIENCE: GROWTH, DEVELOPMENT, AND UTILIZATION OF CULTIVATED PLANTS. Englewood Cliffs, NJ: Prentice-Hall. Editors of Sunset Books and Sunset Magazine. (1988). WESTERN GARDEN BOOK. Menlo Park, CA: Lane Publishing Co. Evaluation: Unit Exam ===================================================================== *** INSTRUCTORS PLEASE NOTE *** The detail of this topic presentation goes beyond the scope necessary to meet the requirements of the Core Cluster in this area. It will take longer to teach than indicated above if covered entirely. It is included for local enrichment as appropriate to the class. ===================================================================== TOPIC PRESENTATION: A. Seedbed Preparation: While many ornamentals are propagated from cuttings and other vegetative means, seed is used to start billions of dollars worth of horticultural products every year, especially in the bedding plant industry. 1. Importance of Seedbed Preparation: In the production of ornamentals from seed, preparation of the seedbed is of paramount importance. a. There is no time in a plant's life cycle that it is as susceptible to disease, dehydration, and trauma as when it is first germinating. The environment prepared for seed germination must be hospitable to sensitive seedlings. b. Strong, uniform seedlings yield strong uniform plants. Seed germination is the starting point for successful production of ornamentals. c. High quality hybrid seed is expensive, and all efforts should be made to make germination a success. All subsequent nursery operations depend on this. 2. Characteristics of a Good Seedbed: The main thing a germinating seedling needs from the seedbed is a disease-free environment which provides a constant supply of air and moisture to the seed as it germinates. How this requirement is met in the field is different from how it is met in the greenhouse, but in either place the germinating medium should: a. Be of fine texture, so the seed can be in close contact with growing media (soil) particles. (This will insure that moisture in the media can reach the seedling.) b. Be free of large clods and debris that might physically block the germinating seedlings or intercept water. c. Have good drainage so seedlings receive plenty of air. The subsoil should be permeable to air and water, thereby providing adequate drainage. A loose, crumbly structure is ideal. d. Be free of fertilizers or other salts which would compete with seedlings for moisture. (Along these lines, be sure no pre- emergent herbicides have been used in the area for over a year.) e. In the case of seedlings which will be transplanted, be composed of a medium which crumbles easily for separation at transplanting. 3. Seedbed Preparation in the Field: Good seedbed preparation is essential for successful field and garden sowing. a. Field Planting: For a large-scale nursery planting in the field, a tractor is required. Some or all of the following equipment may be employed, as described: 1) The plow may be used as the first step in preparing the seedbed. It inverts the soil and covers crop residues, but often leaves the soil in lumps that must be broken into smaller size. 2) Disks are used to reduce clod size by fracturing them with shearing and pressure. Sometimes the disk can substitute for the plow, especially when the soil is in good tilth. 3) The harrow is used to further reduce the size of the soil clods left after discing. It smooths and levels the soil and destroys small weeds. 4) A lister is a small plow with a double moldboard that produces a ridged furrow. The lister is often followed by a drill for planting and covering the seed. 5) If the field is level, and tillage operations are conducted carefully, the seed can be irrigated by furrow. In this case, capillary action of the soil will bring moisture into contact with the seed. 6) If the field is on a slope, sprinkler irrigation should be used to germinate the seed. b. Sowing Seed in the Garden: On a small scale, mechanized equipment is optional. The following procedure should yield a quality seedbed: 1) Check the soil. Most loamy soils, if correctly tilled, will serve well for a seedbed. a) Loam or sandy loam soils are excellent. b) WELL DECOMPOSED organic matter added to the seedbed will enhance aeration and moisture retention. c) Too much organic matter, or that made up of coarse undecomposed particles, will result in poor seed to soil contact and failure to germinate. d) If in doubt about soil quality, this is the appropriate time to have it tested. Take a sample and send it to a good lab. This can prevent a lot of grief and expense later. 2) Prepare the Soil: a) A rotary cultivator can be used to turn and loosen the soil to the desired texture. b) A loose, crumbly soil is desirable and easy to work. (Note: Soil should not be worked if it is too moist. This will result in damage to the soil structure, which is very undesirable in the seedbed.) c) Amendments, if any are needed, should be added at this time. A pre-plant fertilizer such as a slow- release pelleted material can be incorporated if desired. d) If a rotary cultivator is not available, use a spading fork or a garden spade. 3) Grade the soil: a) Rough and fine grading should provide a bed that is level, especially if furrows will be used to water the crop. b) The soil can be lightly rolled at this time if some settling is required after tilling. c) Tools useful for grading include the landscape rake, the bow rake, the level-headed rake and the square- point shovel. For larger areas a drag (similar to a chain drag used with a tractor) can be fashioned from boards and rope. d) Large clods can be raked together and buried. 4) Create rows and furrows. a) If the garden area is large, planting in rows will facilitate weeding, fertilizing, harvesting, and other operations. b) In raised beds or small gardens, rows can be a waste of space. c) Bow rakes, pointed shovels, and hoes are all useful for making furrows. On a larger scale, rotary cultivators can be adapted to do this job. 5) Plant Seeds: a) Seeds can be planted on top of the row or in the low basin of the furrows. b) Both work, although care must be taken not to drown the seedlings planted in the furrows. Likewise, care must be taken to be sure seeds planted at the top of the rows get adequate moisture. c) Use a warren hoe or a trowel to open a trough for seeds. See discussion below regarding planting depth. d) Place seeds in trough, and cover with soil in a uniform manner. e) Firm the soil to put the seed in good contact with the soil. f) Manually operated seed drills can be used for large plantings. These combine the last three steps listed above into one. 5) Irrigate to Initiate Germination: a) This is the most critical period for irrigation. Germinating seeds have little or no root system. They can't get to the water--the water has to get to them. b) The seedlings have no reservoir of water. There must be a constant availability of water or desiccation (drying up) will occur quickly. c) Be sure that the irrigation method used does not crust the soil too badly (some crusting is inevitable with sprinkler irrigation) or wash away soil. 6) Control Pests: a) Planting time is a good time to think about controlling pests. b) Snails, slugs, rodents, and other pests that could damage tender seedlings as they emerge should be dealt with before germination rather than after. 7) Withhold Fertilizer: Fertilizing too soon can burn the roots of emerging seedlings. If you need to add fertilizer wait until the stand of seedlings is well established. c. Depth of Planting: Whether in the field or the backyard garden, depth of planting is critical in that it will determine the rate of emergence, the density of the stand, and, in some cases, whether the seed emerges at all. 1. If the seed is planted too shallow it may dry too rapidly. 2. If it is planted too deep, emergence of the seedling will be delayed, or, in extreme cases, the seedling may not be able to emerge. 3. Depth of planting is determined by the kind and size of the seed, the condition of the seedbed, and the environment at planting time. 4. A rule of thumb is to plant seeds to a depth of four times the average diameter of the seed. __________________________________________________________ ACTIVITY: 1. Have students prepare a seedbed, as described above. Plant bachelor's buttons, strawflowers, dianthus or any other flowers that might be cultivated in the field. 2. Have students experiment with different depths of planting seed and decide, as a class, what the best depths are for various species. __________________________________________________________ 3. Germinating Seed in the Greenhouse: Some seed is too fine and delicate to survive field conditions, and must be germinated in the greenhouse. Also, plants which are to be grown on in containers must be started in a way that will make them easy to transplant, usually in flats. a. Materials, Tools and Equipment: For general seed germination, the following materials are useful. 1) Flats: a) Sturdy flats which minimize the shifting of germinating medium are best. b) Special flats which have molded rows for sowing seed are available, but not necessary. c) Flats should be new out of the box or well sterilized. Dirty or recycled flats can be disastrous for germination. 2) Germinating Medium: Germinating medium affects both the germination process and the transplanting process. Necessary qualities include: a) Impeccable cleanliness. The germination medium is the last place pathogens are needed. b) Excellent drainage. c) Superior water retention. d) A loose, crumbly quality to facilitate transplanting. A loose medium, without too much stringy peat moss, makes it easier to tease seedlings apart. e) Low nutrient levels. f) Uniform composition. One good germinating medium is composed of fine peat moss, perlite, vermiculite, and sharp sand. 3) Top Dressing Materials: These can include vermiculite, saran wrap, newspapers, or simply more germination medium. 4) Fine sand, for helping to sow fine seed. 5) Flat tamps, for firming the seed into contact with the soil. 6) A thermostatically controlled heating pad, by which germination flats can be maintained at a constant temperature. 7) If there is any doubt about fungus organisms, a fungicide to discourage damping-off organisms. (Examples are Captan, Banrot, and Terrachlor.) 8) A mist nozzle for irrigation. b. General Seed Sowing Methods: Seed can be planted automatically or by hand. 1) Special seeding machines and plug trays which yield flats of several hundred individually planted seedlings are available in the nursery trade today. The machines are costly, but result in labor savings both in seeding flats and, especially, in the transplanting process. 2) Manual planting: Most seed is still planted by hand. The following recommendations will improve success in germinating most seed types: a) Pre-irrigate germinating medium, rather than having to apply a lot of water after sowing. Fungicidal drenches, if necessary, should be applied at this time. b) Sow seed evenly. Pass over the flat several times with the seed for that flat, sowing from different directions each time. This will insure an even stand of seedlings. (Some growers plant seeds in rows. This works well too.) c) After sowing, gently press seed against growing medium with a flat tamp to insure intimate contact between the seed and the germinating medium. This will help the seed get the moisture it needs. d) Provide constant bottom heat for germinating seeds. Different species vary in their heat preferences, but a temperature between 70 and 80 degrees Fahrenheit is good for most seeds. e) If possible, don't disturb flats or germinating medium once seed has been planted. Wait until leaves show before moving flats around. f) Monitor moisture carefully. Seedlings will die quickly if flats go dry, especially if they are sitting on a heating pad. There is little danger of this with fast-germinating species, but if flats sit a long time, soil moisture will evaporate. g) Always label the flats as you plant them with the date, the name or variety of the plant, and any special treatment applied. h) If necessary, seedlings can be "held" with growth regulators until they are ready to transplant. Not all species respond well to this treatment. c. Specific Sowing Techniques: Different seeds have different requirements in how they are handled at sowing. Because heat is provided from below, and moisture levels are constant, planting depth is not the concern it is for seed sown in the field. In the greenhouse, the concern is how seed is covered. This depends on the seed type. 1) Seeds Requiring Darkness: Some seeds must have darkness to germinate. This is nature's way of saying, "You are planted deep enough and will have the moisture needed to germinate successfully." a) These seeds should be covered with a thin layer of sowing medium or vermiculite. The covering should then be gently misted until saturated. b) Enough covering should be used so the seed is not visible. About 1/8th inch is plenty in most cases. c) Vermiculite is an excellent material for this purpose because it holds a lot of moisture, an important requirement for germinating seedlings. d) The use of a water-retentive material makes a second covering (to retain moisture) unnecessary. 2) Seeds Requiring Light: This is frequently a requirement for small seeds. In this case, nature is saying, "You are not buried too deeply, and will not be prevented from germinating by thick layers of soil." a) This kind of seed should not be covered with medium. b) A layer of plastic wrap or a single thickness of newspaper will allow light through to stimulate seed germination. c) Since these seeds have no moist media covering them, other steps must be taken to prevent desiccation. Solutions include misting, plastic or glass coverings, high humidity in the germination chamber. 3) Some seed will germinate under either condition. In this case, cover the seed with vermiculite, and worry less about trying to keep seed moist. __________________________________________________________ ACTIVITY: 1. Have students plant coleus seeds by each of the two methods described above. At the end of two weeks observe the difference in the seedling flats and discuss which method is preferable for coleus. __________________________________________________________ 12/14/90 MH/sg #%&C