Root Substrates

1. Root Substrates Image source: Reed, D. 1996. Water, Media, and Nutrition for Greenhouse Crops. Ball Publishing. Batavia, Illinois.

2. Three Basic Types of Root Systems: Smith. 2000.The Vegetable Gardener’s Bible. Storey Books. Pownal, VT. Storage Taproot Taproot Fibrous Source: Raven, Evert, and Eichhorn. 1986. Biology of Plants. 4th Ed. Worth Publishers, Inc.

3. Root Functions • Anchoring the plant (citrus tap root) • Absorbing water and minerals from the soil and transporting them to the stem • Food Storage (Carrot) • Aeration (Black Mangrove and Cypress; pneumatophores) • Support (Red Mangrove and Corn; Proproots)

4. Root Systems Consist of: • Primary Roots • Secondary Roots • Root Hairs Image Source: Capon. 1990. Botany for Gardener’s. An Introduction and Guide. Timber Press. Portland, OR. Link to website

5. Root Hairs • Root hairs are tubular extensions of epidermal cells • Increase root surface area • Greatly increases plants ability to absorb water and minerals from the soil Image Source: Capon. 1990. Botany for Gardener’s. An Introduction and Guide. Timber Press. Portland, OR.

6. Link to Website

7. Link to Website

8. Root Substrate Functions • Reservoir for plant nutrients • Hold plant available water • Provide means for gas exchange • Provide anchorage for the plant

9. Use of Field Soil in GH • Used where plants are produced in in-ground beds (some cut flowers, some greenhouse tomatoes) –issues with disease build-up • Many greenhouses are located in areas without a good supply of field soil for potted plants (even if available – environmentally unsound) • This lecture will focus mostly on soilless media for the greenhouse production of bedding plants and ornamentals

10. Root Substrate Properties • Stability of Organic Matter • Carbon-to-Nitrogen Ratio • Bulk Density • Moisture Retention and Aeration • Cation Exchange Capacity • pH

11. Organic Matter Stability • You want minimal decomposition of organic matter during the production cycle • Decomposition reduces substrate volume and produces finer texture – reducing water holding capacity and aeration simultaneously • Exceptions: in ground vegetable and flower production – in this case organic matter breakdown is acceptable – organic matter is replenished on an annual basis

14. C:N Ratio • You must take this ratio into consideration when managing organic matter • C:N ratio should be 30:1 or less – when more carbon is present microorganisms will use the nitrogen from fertilizer • Microorganisms that break down the organic matter and ultimately make nutrients available for plant growth require N for protein • Initially they may actually tie up nearly all the nitrogen during the decomposition process. C:N ratio for sawdust is 1000:1 • Warmer temperatures accelerate the decomposition process.

15. Bulk Density • Bulk density important for containerized crops • If a media is too light pots may topple when the media begins to dry out • Benefits of heavier root substrate choices must be balanced with the additional costs of handling and shipping

16. Moisture Retention and Aeration • 3 components of a substrate • Solid particles • Liquid water coating particle surface • Pore space • After watering 10-20 percent of the volume of the Root substrate should be occupied by air

18. Desirable Root Substrate Properties • Any organic matter should be stable • C:N ratio of at least 30:1 (less better) • Bulk Density: 40-60 lbs/ft3 • At CC 10-20% of root substrate volume should be air • CEC 6-15 me/100 cc is acceptable • pH – for most crops 6.2-6.8

19. Other Issues for Consideration • Water Content vs. Container Height • Container Size

20. History of Mixes • Most soilless mixes used today are derived from two research programs • Dr. Baker from the University of California (5 mixes and 6 base fertilizers; 30 combinations) • Dr. Boodley and Sheldrake at Cornell (most popular) – nutritional additives based on crop • Overall most common is 50% peat, 25% vermiculite, and 25% perlite

21. FAFARD® MIX #2. For germination mixture, packs and pots up to 10 inches. Canadian Sphagnum Peat Moss, Horticultural Vermiculite, Horticultural Perlite. Bag Size: 2.8 cu. ft. Wt. 9 to 12 lbs. per cu. ft. FAFARD® MIX #3. For 4-inch and larger; pots and baskets. Canadian Sphagnum Peat Moss, Horticultural Vermiculite, Horticultural Perlite, Aged Pine Bark. Bag Size: 2.8 cu. ft. Wt. 14 to 17 lbs. per cu. ft. FAFARD® MIX #3B. Suitable for a wide range of crops, from seedlings to packs to baskets. Canadian Sphagnum Peat Moss, aged Pine Bark, Vermiculite and Perlite. More peat and less bark than #3. Bag Size: 2.8 cu. ft. Wt. 12 to 15 lbs. per cu. ft. FAFARD® MIX #3S. An economical soilless mix for packs, pots and baskets composed of Canadian Sphagnum Peat Moss, Vermiculite, Aged Pine Bark, Polystyrene Beads. Bag Size: 2.8 cu. ft. Wt. 12 to 15 lbs. per cu. ft. FAFARD® MIX #4. A finer textured mix with greater water-holding capacity than 3B, for pots and baskets. Excellent for drip or subirrigation. Contains Canadian Sphagnum Peat Moss, Aged Pine Bark and Vermiculite. Bag Size: 2.8 cu. ft. Wt. 12 to 15 lbs. per cu. ft.

22. Growing Mix No. 2. A versatile soilless mix composed of Canadian Sphagnum Peat Moss, Vermiculite and Perlite, plus starter nutrients and wetting agent. Ready to use direct from the bale—no mixing or sterilizing! We recommend it highly for growers as a time- and money-saver. 3.8 cubic feet compressed bale. H6658-9—1-49 bales, $21.00/bale; 50-100 bales, $19.25/bale Growing Mix No. 1P. This economical peat-based growing mix contains 2 main ingredients: Canadian Sphagnum Peat Moss and Perlite. It meets Fafard®’s high quality standards, pH adjusted, and contains starter nutrients and wetting agent, but by not adding vermiculite; passing savings along to you! 3.8 cubic feet compressed bale. H6732-7—1-49 bales, $19.85/bale; 50-100 bales, $18.25/bale

23. METRO-MIX 366-P W/SCOTTS COIR Mix contains 30-40% processed coconut coir pith along with medium grade vermiculite, composted pine bark and hort perlite. Includes starter nutrient charge and wetting agent. Ideal for potted plants, bedding and hanging basket production. 5.2-6.4 Ph range after wet-out. Weight approx. 48 lbs. METRO-MIX 380 A blend of composted pine bark, medium grade vermiculite, Canadian sphagnum peat moss and hort. perlite, combined with a starter nutrient charge and wetting agent. A moderately coarse mix ideal for potted and bedding plants, landscape applications and garden mums or stock plants. Ph range of 5.0-6.5 after wet-out. Weight approx. 45 lbs. METRO-MIX 510 This mix contains sphagnum peat, vermiculite, composted pine bark, processed bark ash, wetting agent and nutrient charge. It has a coarser texture and is useful for long-term growing-on of hanging baskets, potted plants, nursery container plants and interiorscapes. pH range after wetting is 5.3-6.7. Weight approx. 56 lbs. METRO-MIX 700 An excellent coarse mix with outstanding aeration, percolation and nutrient retention characteristics. A blend of Canadian Sphagnum peat moss, vermiculite, perlite, moderately coarse composted pine bark, wetting agent and nutrient charge. pH range is 5.3-6.5 after wetting with acid forming fertilizers. Weight approx. 57 lbs.