Compost Ingredient and its Use in Crop Cultivation

The present invention relates to a novel compost ingredient. It further relates to the use of the compost ingredient in the cultivation of crops, especially in the cultivation of potted plants (particularly although not exclusively nursery stock plants) and mushrooms (particularly although not exclusively Agaricus mushrooms).

BACKGROUND OF THE INVENTION

Potted plants, including nursery stock are cultivated using composts (growing media). The compost is normally peat and/or bark although other materials such as loam, perlite and vermiculite are also used.

In the UK, about 400,000 cubic metres of peat are used for nursery stock production annually. The other main nursery stock producing countries in western Europe are the Netherlands and Belgium, both of which import peat and together use an estimated 2 million cubic metres of peat for nursery stock production annually.

The amount of peat used in nursery stock production and other applications has given rise to significant environmental concern. There has therefore been a considerable amount of research into the use of different materials for nursery stock composts, including an extensive amount of work examining peat alternatives.

The alternative materials have generally given inferior plant growth results than peat- based composts. This has usually been due to inferior water-holding capacity and/or immobilisation of nitrogen, resulting in nitrogen deficiency of plants. Alternative materials may also be more expensive than peat.

Nursery stock plants are grown over several months or years. During this period, the plants require a steady supply of plant nutrients. This has led to the development of slow release fertilisers. These are normally in the form of a resin coated pellets containing various fertilisers. Their use has avoided the need to apply plant nutrients

throughout the growing period of a plant, but they add significantly to the cost of the compost. The use of organic materials, such as raw wool wastes or 'shoddy', has been unsuccessful due their very slow degradation and release of nutrients, adverse effects on the water-holding characteristics of the mixed compost, contaminants such as grease (lanolin), dirt, and weed seeds, and difficulty in mixing and blending the materials into the compost.

Pelleted wool waste from wool washing (scouring) plants has been tried as a compost additive. This is known as "WULPAK". It contains long wool fibres and contaminating materials such as lanolin, and dirt. The long wool fibres and contaminating materials, as well as weed seeds in the wool waste, means that forming into large pellets is necessary. This reduces integral and uniform mixing of wool fibres with other growing media components and the contact between the roots of plants and the nutrients in the waste. Pelleting also adds significantly to cost.

Shredded carpets comprising bits of yarn and backing materials have been tried as soil additives (see US 6,032,410 and US 6,022,827). The carpets are mixed with sand and/or soil and are primarily used as a root support matrix, rather than a source of nitrogen. The yarns in the carpet may be nylon, polypropylene or polyester or, optionally, wool. The shredded carpet includes backing material, such as jute and latex adhesive. The addition of cellulosic materials, such as jute, results in a decrease in the amount of nitrogen released by the carpet when wool is used, because the jute is broken down by bacteria which decrease the available nitrogen in the soil. The backing material increases the average particle size and reduces the uniformity of particle size that can be achieved by shredding. The need for shredding also increases cost.

Mushrooms, especially Agaricus bisporus and other Agaricus spp., are cultivated using a composted substrate (compost). The compost is prepared from a carbon source such as wheat straw and/or other types of straw, a nitrogen source such as various animal manures and urea, and other ingredients such as gypsum and chalk. The use of animal manures, such as poultry and horse manures, in mushroom composting can result in significant nuisance odours. After preparation of the compost, mushroom inoculum (spawn) is added to the compost, which then becomes

colonised (spawn-run) with mushroom mycelium. At the time of adding spawn or after the compost has been spawn-run, protein-rich supplements such as soya meal- based products, can be added as a nutrient source for the mushroom mycelium.

The objective of the present invention is to provide a compost ingredient capable of providing:

• a partial or complete alternative to peat in the cultivation of potted plants

• a nutrient source, particularly of nitrogen, in the cultivation of potted plants and mushrooms while improving plant growth or mushroom yield and/or crop quality.

SUMMARY OF INVENTION

The invention provides a compost for cultivating crops, the compost including short wool fibres, the use of such compost in crop cultivation (especially potted plant and mushroom cultivation) and methods of cultivating crops (especially potted plants and mushrooms) using the short wool fibres. The compost is especially useful for horticultural purposes.

Short wool fibres are by-products derived from carpet shearing machines, in the shearing of wool-based carpets. The tips, usually up to 3 mm long, of the pile are sheared-off with blades to leave a uniform pile on the carpet. Vacuum (suction) extraction of the waste fibre tips (flock waste) produces a suspension in air of short fibres that are then collected in suitable containers such as polythene or hessian bags. The short fibre material comprises wool, and may contain other natural and synthetic fibres (e.g. nylon, acrylic, polypropylene).

The use of the short wool fibres in compost according to the present invention provides a number of advantages:

• reduced peat consumption for potted plant compost by substitution with a waste by-product (environmental benefits)

• a peat alternative or substitute in countries where good quality peat is unavailable (USA, Australia)

• a slow release source of nitrogen and other nutrients for plant growth

• a nitrogen source for mushroom compost, leading to higher mushroom yields and reduced composting odours compared with using animal manures

• a protein-rich supplement for use in prepared mushroom substrates, leading to higher mushroom yields and/or quality

• the short fibre length facilitates uniform and integral mixing with other compost ingredients such as peat and bark

• the wool content has been washed and heated so that it is free of contaminants present in unwashed wool (grease, dirt, animal manure, weed seeds)

• the avoidance of landfill which is currently used for disposal.

PREFERRED EMBODIMENTS

It is preferred that the short fibres are wool fibres such as those derived from the mechanised wool-based carpet industry. The wool in such fibres provides a source of nitrogen for plant growth and mushroom composting, and a source of protein for mushroom growth.

The short wool fibres are obtained from carpet shearing machines and are collected under suction (vacuum extraction) in dust extraction units. Currently the material is disposed of on to landfill heaps; this involves a transport and handling cost.

The short wool fibres are usually, but not exclusively obtained from one of the following types of wool-based carpet production: Axminster, Wilton, woven, tufted, needled, needpunch, foam-backed. Suitable carpet shearing machines are produced by, but not exclusively by Sellars Engineers Ltd, Huddersfield (UK), by Paulus Joseph SA, Welkenraedt and HBC Belgium SA, Dison (both Belgium) and by Tornado Textilmaschinen, Alsdorf, M-tec Textilmaschinen GmbH, Viersen, Xetma Gematex GmbH, Aue and Munsinger Sondermaschinen, Knittlingen, Germany.

Suitable fibres are predominantly wool-based and short. By 'short fibres' in the present specification is meant fibres of sufficiently short length such that, in use, compost including the short wool fibres has:

• sufficient volumetric water-holding capacity ^

• availability of nitrogen, protein and/or other nutrients to enable crops to grow in a yield and/or with quality substantially equivalent or superior to that obtained using peat- or bark- based composts (in the case of potted plants) or composts containing other nitrogen sources or protein supplements (in the case of mushrooms). The fibres must also be of sufficiently short length to enable mixing and blending with other compost ingredients.

By 'wool fibres' in the present specification is meant fibres consisting predominantly of wool, i.e. at least 50% w/w (weight/weight) wool of mammals, usually but not exclusively lamb's or sheep's wool.

Preferred short fibres are of sufficiently short length such that they have a volumetric water holding capacity of 35 — 55 % v/v (volume/volume), and especially 38 — 51 % v/v (the volumetric water holding capacity or 'water volume' is measured according to European Standard EN 13041:1999).

Suitable short wool fibres may be predominantly less than 3 mm in length (i.e. more than about 50% w/w are shorter than 3 mm). In a preferred embodiment, the short wool fibres are of sufficiently short length that at least 50% w/w are shorter than 3 mm, and at least 40% w/w are shorter than 2 mm. The above fibre lengths exclude mixing or adulteration with other materials before measurement.

The new compost (growing media) of this invention can be made by mixing short wool fibres with a conventional compost (growing media) ingredient such as peat or bark, at a level preferably not greater than the volume of the conventional material. Preferably the usage is from 0.5% to 50% by volume of short wool fibres, more typically 5% to 30%, preferably about 20%.

For mushroom cultivation, the new compost of this invention is preferably made by mixing short wool fibres with other conventional mushroom compost ingredients such as straw and poultry manure and may include inorganic materials such as gypsum, at a level preferably not greater than the weight of the conventional compost ingredients.

Preferably this is from 0.1% to 50% by weight or preferably by volume of short wool fibres, more typically 1% to 10%, especially about 5%. Alternatively, the short wool fibres can be added to the prepared compost at similar inclusion rates to those envisaged for use as a mushroom compost ingredient.

The short fibres may contain natural and synthetic fibres, such as nylon, acrylic and polypropylene. Preferably less than 50% w/w, most preferably less than 25% w/w, especially 10 to 20% w/w of additional fibres are present.

Preferably cotton is not present in the short fibres. Cotton is broken down by microbes in the compost. This chelates nitrogen in the soil as it is used by the bacteria. This reduces the amount of nitrogen available for plants. Preferably the maximum amount of cellulosic material such as cotton in the short wool fibres is 20% w/w (before mixing with the compost).

EXAMPLES

Fibre lengths and compositions of suitable and unsuitable fibres are shown in Tables 1 and 2.

TABLE 1. Fibre lengths of suitable and unsuitable wool fibre samples

* Unsuitable due to high cotton content, not due to fibre length

TABLE 2. Compositions of suitable and unsuitable wool fibre samples

^! Unsuitable due to fibre length, not due to wool content

The Applicants have used short wool fibre at an inclusion rates of 12.5 to 50% v/v in peat-based and peat-bark growing media for a range of nursery stock plants:

Berberis 'Superba' Ceanothus 'Repens' Clematis montana 'Tetrarose' Cotoneaster εichholz' Cytisus 'Boskoop Ruby' Delphinium 'Guardian Blue' Digitalis parviflora 'Milk Chocolate' Euonymus rubra var macracantha Geranium 'Sabani Blue' Griselinia littoralis Hydrangea Ia France' Lonicerajaponica 'Halls Prolific' Lavendula 'Purple Wings' Nepeta 'Nimbus' Spireaea japonica 'Candlelight' Spiraea japonica 'White Gold'

Verbena 'Claret'

Viburnum tinus 'French white'

Viburnum tinus 'Pupureum'

Tomato (Lycopersicon esculententum cv Moneymaker) were also used.

The plants were grown as 'liners' in 9 cm posts and as finished plants in 2L or 3L pots. The same rates of controlled release fertiliser (Sincrocell or Osmocote) and base fertiliser were used in all the mixes.

In all the above species, plants grown with the addition of short wool fibres (at 12.5% v/v or higher) produced a greater plant weight and had darker green leaves than plants grown in the non-amended peat or peat-bark mixes (Tables 3 and 4).

TABLE 3. Effect of amendment of peat and peat-bark growing media with short wool fibres at different inclusion rates on the plant top dry weight (g) of various species and cultivars. Each value is the mean of at least 6 replicate plants.

TABLE 4. Effect of amendment of peat and peat-bark growing media with short wool fibres at different inclusion rates on the top leaf colour score ^a of various plant species and cultivars. Each value is the mean of at least 6 replicate plants.

^a leaf colour score, 1 = palest, 3 = darkest ^b peat or ^c 85% peat + 15% bark ^d least significant difference, using a Student's t test at a level of probability of P = 0.05, between plants grown in the unamended control medium (peat or 85% peat + 15% bark) and the same medium amended with short wool fibres at 12.5, 25 or 50% v/v

Mushroom compost was prepared with 4.3% w/w short wool fibres (other compost ingredients %w/w were wheat straw 70.4, poultry manure 21.1 and gypsum 4.2). This was compared with a standard mushroom compost formulation (% w/w wheat straw 59.8, poultry manure 36.0, gypsum 4.2). The inclusion of the short wool fibres in the compost as a nitrogen source resulted in a less odorous compost due to using 41.1% less poultry manure. The inclusion of short wool fibres in the composts also resulted in a slightly higher mushroom yield (Table 5).

TABLE 5. Mushroom yields (kg/tonne spawned compost) obtained from composts prepared from straw, poultry manure and gypsum (control) and from straw, poultry manure, gypsum and short wool fibres. Each value is the mean of two replicate crops and 16 replicate trays per crop.