There are several media and mixtures of different kinds available for use in propagation such as in seed germination, rooting of cuttings and for growing container stock. Commonly used media with a brief description of properties are given below-
Soil is the most important and widely used media in the world, also called “Universal Media‟. A soil is composed of materials in the solid, liquid and gaseous states. This material must exist in the proper proportions for satisfactory plant growth. The texture of soil depends upon relative proportions of sand, silt and clay. Maintenance of soil structure in favorable and granular form is very important.
Sand consists of small rock grains (0.05-2.0mm in diameter) formed as a result of the weathering of various rocks. Its mineral composition depends upon the type of rock. Quartz sand is generally used for propagation and plastering grade sand is used for rooting of cuttings. Sand should be preferably sterilized before use.
There are different types of peats available. Peat consists of the remains of aquatic marsh or swamp vegetation, which has been preserved under water in a partially decomposed state. Composition of peat varies widely depending upon the type of vegetation, decomposition and degree of acidity. It is a uniform product, free from pests, diseases and weed seeds, useful for growing rooted cuttings or seedlings. Peat is easily compressed and can be purchased in polythene bags. Peat is the material most commonly used with many other different propagation media. Peat can be mixed, with either fine or coarse sand, perlite or vermiculite, or sawdust. Peat is formed by the partial decomposition of plants in areas of high rainfall and the types of peat can vary considerably in colour and structure. A medium grade sphagnum peat is generally recommended as a nursery medium.
The Sphagnum moss is the dehydrated remains of acid bog plants of the genus Sphagnum. It is relatively sterile, light in weight and contains specific fungi static substances. It has a higher water holding capacity. It absorbs water 10-20 times of its own weight.
It is a micaceous mineral, which expands markedly when heated. It is chemically a hydrated magnesium-aluminium-iron silicate. It is very light in weight, neutral in reaction with good buffering properties and insoluble in water. Normally has a pH range between 6.0-6.5. It is normally mixed with peat moss, because vermiculite alone will not support the cuttings. It is suitable for rooting the cuttings intended for export to overcome specific plant quarantine regulation.
It is grey coloured material of volcanic origin mined from flows and has natural reaction with no buffering, cation exchange capacity and mineral content. Chemically perlite is made up of alumino-silicates. It is a light sterile material containing no nutrients. It has a pH of 6.0-7.5. It may be used alone but it is best used with peat moss for woody ornamentals. Since there is little chance of damage to the structures from weight stress.
It is grey or white coloured volcanic rock, which was originally formed from the gases to give it a sponge-like porous character. It is made up of aluminium silicate and also contains small quantities of potassium and sodium. It provides good aeration and drainage to medium.
Leaf mould can be prepared by placing leaves and soil in alternate layers. For accelerating decomposition, a small quantity of ammonium sulphates is added. Leaf mould becomes ready within 12-14 months. This material is rarely used in modern large scale propagation structures.
Sawdust and Wood Shavings
These are mostly used for propagation media. A byproduct formed during the processing of wood material. It is free from salt nitrogen deficiency, if sawdust is excessively composed of, there is a problem of drainage. Controlled release fertilizers can be used along with sawdust.
It is also called as coco dust. Byproduct of coconut processing for fiber production. It is the most popular growing media available these days. It has excellent aeration of 15-25 per cent because of its fine structure. Coco-substrate is expected to degrade slower than other substrates such as peat moss. Potassium is not added in this medium as it is already available in coir. This medium requires the addition of more nitrogen as microorganisms in coco peat need to break down easily degradable substrates present in Coco peat.
Since container-grown plants rely on regular watering to survive, some mixes contain polymers to hold moisture. Polymers, which may look like tiny plastic marbles, act like sponges. They absorb and hold water when the medium is moist, but release it back into the soil when dry. This helps maintain a consistent level of moisture for plant roots. Several different brands and forms of polymers are available at local nurseries.
Media Preparation for Nursery
In a Nursery the propagated young seedlings or rooted cuttings are sometimes planted directly in the field but frequently they are planted in soil mixtures in some type of container such as peat or plastic pots or clay flower pots or metal cans. Potting mixtures for rooted cuttings and young seedlings generally contains 1 part of sand, 1 part of Loam soil and 1 part of peat moss or shredded bark or leaf mould is generally recommended as potting mixture.
Potting Mixtures and Potting Yard
For better success of nursery plants a good potting mixture is necessary. The potting mixtures for different purposes can be prepared by mixing fertile soil, well decomposed FYM, leaf mould, oil cakes etc. in different proportions. The potting mixture may be kept near the potting yard, where potting and packaging is carried out. Sand, Loamy soil, FYM in 1:2:1 proportion is generally used to grow vegetable seedlings in raised beds.
Media Combinations for Vegetable Nursery
Loamy soil + Sand + FYM + Vermicompost
Loamy soil + Sand + FYM + Biofertilizers
Loamy soil + Sand + Vermicompost + Biofertilizers
Loamy soil + Sand + Vermicompost + Oil cakes + Biofertilizers
Loamy soil + Sand + Compost + Biofertilizers
Loamy soil + Sand + FYM + Oil cakes
Loamy soil + Sand + FYM + Oil cakes + Biofertilizers
Loamy soil + Sand + Leaf mould + Oil cakes