GB2137609A - Growing medium for plants - Google Patents

Abstract

A growing medium for plants comprising coir dust as the major constituent, measured by volume, and fertiliser.

Description

SPECIFICATION Growing medium for plants The present invention relates to a growing medium for plants.

Although plants have traditionally been grown in soil, the difficulty and expense of obtaining adequate supplies of good quality loam, and especially of sterilising it, has led in recent years to an ever-increasing dependence by professional and amateur plant growers on soil-less growing media or composts, usually confined within a pot or other type of container.

Those composts which are most widely used at present are based on peat, but the supply of this material is now becoming limited with the result that peat-based growing media are becoming increasingly expensive.

We have now found that certain compositions based on coir dust are extremely well suited for use as a growing media for plants. Coir dust is obtained from the retted husks of the nuts of the coconut plant (Cocos nucifera L). The husk of the coconut comprises both fibrous and particulate material. Separation of the fibrous material from the remainder of the husks leaves a residue of small, irregular, particles generally known as coir dust.

According to the present invention there is provided a growing medium for plants comprising coir dust as the major constituent, measured by volume, and fertiliser.

Typically the fertiliser which is present in the growing medium of the present invention is a chemical fertiliser. Examples of the types of fertiliser which may be used as a source of nitrogen are ammonium nitrate, calcium nitrate, ammonium sulphate, urea, calcium ammonium nitrate, potassium nitrate, slow release formulations such as urea formaldehyde, crotonylidene-diurea, isobutyridene diurea, magnesium ammonium phosphate, oxamide, and coated fertilisers such as resinous coated fertilisers and sulphur coated urea. Examples of the types of fertiliser which may be used as a source of phosphorus are superphosphate, triple superphosphate, monoammonium phosphate, diammonium phosphate, polyphosphate, and slow release formulations such as rock phosphate, magnesium ammonium phosphates, calcium metaphosphate, and potassium metaphosphate.

Examples of the types of fertiliser which may be used as a source of potassium are potassium sulphate, potassium chloride, potassium carbonate, potassium nitrate and potassium frits.

If desired, a calcium source may also be incorporated in the growing medium. It is, however, important to use sources of calcium which do not raise the pH of the growing medium to cause it to become too alkaline.

The pH of coir dust is higher than that of peat and it is therefore more advantageous not to use limestone (calcium carbonate), calcium oxide or calcium hydroxide as the calcium source or, at least, as the sole calcium course, but to use instead calcium compounds such as calcium sulphate.

If desired, a source of magnesium may be incorporated in the growing medium. Suitable magnesium sources are magnesium sulphate and magnesium-containing limestone.

It may also be desirable to incorporate a number of micro-nutrients or trace elements in the growing medium. These can be incorporated by including compounds or mixtures, especially those containing boron, copper, iron, manganese, molybdenum and/or zinc, preferably in the form of frits.

Examples of particularly preferred fertilisers are ammonium nitrate, potassium nitrate, superphosphate, calcium sulphate, magnesium-containing limestone and trace element frit.

The fertilisers are included in the growing medium preferably in amounts sufficient to supply nitrogen, phosphorus and potassium in the following quantities: nitrogen 20 - 400 mg/l phosphorus 20 - 200 mg/I potassium 50- 500 mg/l In addition, the physical and/or chemical properties of the growing medium may be altered by adding suitable additives, for example, by adding sand to increase the bulk density of the product.

The coir dust obtained as a raw material is preferably sieved or screened before the fertiliser and other additives are added to it, thereby to remove undesired bulk contaminants from the coir dust.

In a particularly preferred aspect, the present invention provides a sealed bag of plastics or a like material containing a growing medium comprising coir dust as the major constituent, measured by volume, and a fertiliser. Seeds or plants can be grown conveniently by perforating the plastics bag, inserting them into the exposed growing medium in the bag, and watering the growing medium to promote growth of the plants.

In a further preferred aspect of the present invention, there is provided a shaped body formed by compressing a growing medium in accordance with the invention into a desired shape. Typically the shaped body will be compressed to form a block or a container, such as a plant pot, in which a seedling or plant can be grown.

The invention will now be illustrated by the following Example.

Example The following chemical fertilisers: Ammonium nitrate 600g Superphosphate 15009 Potassium nitrate 750g Calcium sulphate 3809 Magnesiun Limestone 3809 Trace element frit WM255 380g were added to 1m3 of a mixture comprising, by volume, 1 partfine horticultural silver sand and 3 parts coir dust which had been passed through a 9.5mm sieve and moistened with 6 times its own weight of water.

Two peat-based mixtures were used for comparison: a mixture known as GCRI Potting Compost I (devised at the Glasshouse Crops Research Institute) and a commercial mixture known as Levington Universal Compost (Fisons Ltd.). Tomato, cabbage and Chinese cabbage seed was sown in 10 replicate 12 cm diam. pots of each mixture. After 7 weeks growth, without additional feeding, the mean top weight (g) of 100 plants of each type grown in the mixture was as follows: Tomato Cabbage Chinese Cabbage Coir dust mixture 2.62 + 0.25 2.44 + 0.3 2.37 + 0.3 G.C.R.I. Potting Compost 2.86 + 0.32 2.60 t 0.33 2.50 t 0.25 Levington Universal Compost 2.28 t 0.20 2.32 + 0.25 2.27 + 0.32 There were no symptoms of phytotoxicity or mineral nutrient deficiency on any of the plants grown in the coirdust mixture.

The results show that the growing mixture of the present invention produces results comparable to, or better than, traditional peat-based potting composts.

Claims (7)

1. A growing medium for plants comprising coir dust as the major constituent, measured by volume, and fertiliser.

2. A growing medium according to Claim 1, wherein the amount of fertiliser is sufficient to provide in the growing medium nitrogen, phosphorus and potassium in the following quantities: nitrogen 20 - 400 mg/l phosphorus 20 - 200 mg/l potassium 50 - 500 mg/l

3. A growing medium according to Claim 1 or 2, wherein the fertiliser is a chemical fertiliser.

4. A growing medium according to Claim 3, wherein the chemical fertiliser is one or more of ammonium nitrate, potassium nitrate, superphosphate, calcium sulphate, magnesium-containing limestone and a trace element frit.

5. A growing medium according to Claim 1 substantially as described in the foregoing Examples.

6. A sealed plastics bag containing a growing medium as claimed in any one of the preceding claims.

7. A method of growing plants which comprises perforating a plastics bag as claimed in Claim 6, inserting seeds or plants into the exposed growing medium in the bag, and watering the growing medium to promote growth of the seeds or plants.