LO 3.8 - Growing media other than soil.

Growing Media * Peat * Bark * Coir * Composted green waste * Perlite * Vermiculite * Rockwool * John Innes Composts * Hydroponics Growing media other than soil

Peat * Almost sterile, free from pests, disease and weeds. * Contains almost no nutrients. * Is light, clean and not unpleasant to handle. Growing media other than soil

Peat * Peat has a high water-holding capacity. it can lead to problems with overwatering and lack of air. * Should not be allowed to dry out, they become hydrophobic and are difficult to re-wet. Growing media other than soil

Peat * It is important not to compact the peat when filing pots – they are ‘loose-filled’ to maintain the air spaces. Growing media other than soil

Bark * Typically conifer bark. Normally the waste of fencing and timber. * Chipped and matured in heaps. * Often contains a certain amount of white wood. * Needs to be well composted/screened. Growing media other than soil

Coir * Coir is a product produced from the outer husks of coconuts. In use since Victorian times. AFP ranges from 24 – 30% useful where waterlogging must be avoided. Growing media other than soil

Coir Disadvantage * The major disadvantage of coir is its inability to hold nutrients. This can be overcome by adding clay minerals. Growing media other than soil

Coir types * Available in different grades. * Pith/dust is very fine, suitable for germinating seeds but can be poorly aerated. Good water holding. * Coarser fibres or chips drain better and give better aeration. * Also available in blocks or sheets. Growing media other than soil

Composted green waste * Good source of potassium and micronutrients * Good water holding * Sustainable * Variable source materials – quality control important * May contain pathogens, herbicides Growing media other than soil

Perlite * Volcanic rock material, crushed and heat-treated, causing it to expand into highly porous white granules. * Sieved into various grades for horticultural use. It improves aeration, moisture retention and drainage. Chemically inert. * Normally added to mixes at 5-20% by volume. Growing media other than soil

Vermiculite * A naturally occurring mineral. When heated it exfoliates, forming concertina-like compressible particles. * Has a large surface area relative to its volume and thus a high cation exchange capacity and buffering capacity. * Used at 5-15% by volume in compost mixes to improve CEC and buffering capacity. * Also improves aeration and water-holding. * Often used as a seed covering.. Growing media other than soil

Rockwool * Rocks (basalt, dolomite) melted at high temperature to form molten matrix, air stream cools the material and forms long fibrous strands. * Good aeration, light, clean. * Used in the form of cubes or sheets, or shredded and mixed with other materials. Growing media other than soil

John Innes composts * John Innes composts were developed in the 1930s, and provided for the first time a formula for a ‘standardised’ compost. * Two drawbacks: (i) difficulty in getting reliable supplies of sterilised loam and (ii) being soil based, they are heavy to transport. * Loam, peat, sand, fertiliser in different proportions for eg pricking out seedlings, rooted cuttings, veg plants, shrubs. Growing media other than soil

Hydroponics * Growing plants in nutrient solutions rather than soil or composts. * Inert material such as gravel, vermiculite, perlite, rockwool used for mechanical support. * Potentially a more efficient and sustainable method of food production than conventional agriculture/horticulture. Growing media other than soil

Hydroponics * Passive systems rely on capillary action * Ebb and flow: tray is regularly flooded with nutrient solution and then drained * Nutrient film technique: constant flow of nutrient solution circulating around roots Growing media other than soil

Hydroponics Advantages * Water conservation: less water is used as water is re-circulated or stored for later use. * Growth rates increase, allegedly by up to 25% * Potential for year-round production * More top growth, less root growth * No soil-borne pests/diseases * No weed problems * Less chemical use * No tillage operations Growing media other than soil

Hydroponics Disadvantages * More complex & more expensive to set up. * Nutrients need to be carefully balanced. * Humid environment can favour fungal disease. * Pump failure can cause whole crop to fail. * Water-borne diseases can spread easily (Pythium, Phytophthora, Fusarium) Growing media other than soil