Current and past developments
Springfield Spray is a leading Chrysanthemum grower in the UK, who in the last three years by customer request has moved from using 100% peat to a mix of 70:30 peat: bark and they have found this to be very successful. However, the retailers have slashed the price of the Pot Chrysanthemum by 30% over the same period of time (Growing Media Association, 2003) and growers such as Springfield are finding it difficult to absorb the extra cost incurred from using high quality bark in their growing media. Using a lower quality and lower priced bark could mean that the standard of the final crop is also lower quality.
Cocopeat or coir is an organic substrate that has been used since the 1980’s. Today it is being developed for use as either 100% growing media or as an additive in potting soils (Keursten, 2005). The reason for this is because of the porosity and excellent water and air holding properties that it possesses. It is also very versatile and can be mixed with other media to suit a wide range of ornamental crops.
New and future developments
Argents Nursery also took part in trials with Langthorns Nursery, Essex to compare peat-free, low-peat and peat-based composts (Remade Essex, 2005). Compost was used with 33% green waste and all the trials produced marketable good quality plants.
Some of the advantages of using green waste were as follows:
- It was not as difficult to re-wet as a peat based compost once dried out, therefore reducing the need for chemical wetting agents.
- The pH was above neutral, which reduces liming costs
- Has a high cation exchange capacity (CEC) which boosts buffering of most plant nutrients. This helps to store plant nutrients and therefore reducing nutrient stress on plants (Peatering Out, 2005). This will cut down on fertiliser costs also.
- Substrates with a coarse texture deter the growth of algae, moss, liverworts and weeds on the surface which reduces hand weeding and herbicide use (Peatering Out, 2005).
- It contains microbes that feed on a range of soil borne plant pathogens which reduces the occurrence of disease
Trials were also carried out in nurseries and colleges in 2003 with support from the Waste and Resources Action Programme (WRAP). These consisted of a wide variety of pot plants (including Aster, Cyclamen, Geranium, Fuchsia, Diascia, Impatiens, and Petunia) being grown in media containing different volumes of peat or peat alternative. The two compost based media were: 33% composted material plus 67% Sylvafibre (composted wood fibre), and 33% composted material and 67% peat. These were compared against the nurseries own mix of peat and bark media and the results showed there to be no significant difference between crops. The media containing composted material still produced plants which were marketable to the same grade as the peat based medias (Gunn, 2004). These trials are still continuing to develop optimum nutrient, irrigation and management levels for the new mixes of growing media. This information is essential if the manufacturers of the media are to convince the nursery growers to invest in their product.
Glasshouse lettuce and cut flower chrysanthemum
Main production techniques and cropping practices
Chrysanthemums are usually grown from cuttings and can be rooted in almost any well drained course medium. This can be anything from cells, flats, strips or pots containing peat-lite media, rockwool or foams (Auburn University, 2005). The cut flower industry is extremely competitive and most growers can not afford to have a crop that is less than grade one. The growing media they use must be suitable to produce plants that conform to the specification that is provided from their clients.
Lettuce is a crop which is highly sensitive to soil conditions and needs a highly fertile soil, ideally with a high available water capacity (Large, 1972). Using a soil-less media means that these factors are easier to control. A soil-less media is also easier to keep sterile and disease free. As the legislation on pesticides and sterilisation methods is being tightened, this is beneficial to any nursery and will also stop the need for methyl bromide fumigation in between crops.
Current and past developments
Lettuce seeds can be sown in to slabs of rockwool in plastic trays for ease of transportation and placed on an ebb and flood bench and covered in transparent covers to keep the humidity levels high. After about 12 days, the seedlings are transported in to a glasshouse and spaced out on to polystyrene trays and floated over ponds (Aesop.Rutgers, 2005). The roots hang through the polystyrene and nutrients are fed to the plant through the water. This is a suitable and proven alternative to growing lettuce in soil beds.
In 2001, 2002, and 2003, research was carried out in Turkey to provide an economic analysis of using a soil-less growing media for lettuce to try and reassure growers that is was a viable alternative (Engindeniz, 2004). These trials proved that the use of soil-less media was a suitable alternative; however a lot of growers are reluctant to make such a huge jump by switching completely to this method.
Studies were carried out in Uganda to find an alternative to using methyl bromide on their cut flower crops after pressure was put on growers from the Ugandan government. All cut flower production was carried out on natural soil and this meant the crop was vulnerable to a build up of nematodes which lead to tremendously high losses. Diseases such as this could mean a huge area of land would be unsuitable for crop production unless fumigated with methyl bromide. The Ugandan government put a deadline at 2015 to ban methyl bromide use, but as in other areas of the world, there is increasing pressure from the consumers to find more environmentally friendly production techniques.
New and future developments
Research is currently being carried out in to the possibility of combining Cod and lettuce production, using a combined Aquaponics system (Lennard, 2005). This involves high intensity systems producing large numbers of fish annually on very small land areas in self contained units. The downside of aquaculture is that fish produce waste and there is always strict environmental legislation about disposing this, but by combining this with lettuce production, it is possible to recycle this waste and also the water that the fish are kept in. 70% of fish waste is water bound and contains mainly nitrates and phosphates which are the main nutrients used for hydroponic plant culture.
Murray Cod are farmed in large tanks with a large gravel bed above the tank. Water is pumped up from the fish tank on to the shelf using a hydroponic system and then returned to the fish tank, so the water is recycled and used to its full advantage. This also solves a problem that some nurseries have with legislation concerning water run off.
For chrysanthemum and other cut flower production, countries such as The Netherlands, Italy, and Denmark are already using substantial amounts of inert soil-less media, such as rockwool and perlite for their crops, but it may be more difficult for third world countries such as Uganda and Kenya to afford this development. Cheaper organic media could be sterilised grain hulls and waste bark could be a more feasible alternative as these are readily available in the area, therefore reducing the importing and transport costs (Pizano and Lorenzo, 2001). Organic compost that is rich in beneficial organisms is also easily available through processing plant refuse and can be used in combination with steam and integrated pest management (IPM) to reduce the risk of pest and diseases.
Conclusion
Both areas covered in this report are shown to be looking for new alternatives to their current growing media. This is either down to the unreliability of using soil and the problems encountered with keeping it pest and disease free, or the pressure from the governments and consumers to find a more environmentally friendly alternative to what they are using. Both areas seem to be shying away from using soil altogether.
Soil-less growing media can be divided in to two categories: organic media (peat, sawdust, straw, and pine bark) and inert media (rockwool, perlite, polyurethane, polystyrene). Organic media (see Appendix 8.1) usually have a good cation exchange and water holding capacity whereas inert media have good water holding capacity, but a lower cation exchange capacity (Pizano and Lorenzo, 2001). This means the grower will usually opt for a mixture of both organic and inert media to get the best results from their crop.
The following factors need to be taken in to account when selecting a growing media for your products:
- Availability- is the source reliable?
- Suitability- can you use it for all your crops?
- Weight and handling properties- this will affect cost of transportation to the nursery and also the need for use of machinery once on site.
- Physical properties such as pH factor, electrical conductivity (EC) levels, air filled porosity (AFP) and initial nutrient levels
- Weed population and sterility- how much work will be needed to sustain the initial quality?
Using green compost in your growing media is cost effective as there is less need to use additional fertilisers, herbicides or buffering agents. This balances out the fact that there might be a need to use higher quality substrates such as bark as part of the media mix. Using ‘green’ media is also beneficial to meet the growing demands of the consumer for environmentally friendly products.
This report shows that the main problem encountered by growers is the reluctance to try a new product until extensive research has been carried out to scientifically prove the benefits.
References
Aesop.Rutgers, (2005) Lettuce Production [www document]. http://aesop.rutgers.edu/~horteng/fhlettuce.htm (accessed 2 January 2006)
Auburn University (2005) Chrysanthemum: Commercial Greenhouse Production [www document]. www.ag.auburn.edu/hort/landscape/Potmum.htm (accessed 2 January 2006)
Bunt, A.C. (1976) Modern Potting Composts. London: George Allen and Unwin Limited
Engindeniz, S. (2004) ‘Growing Greenhouse Lettuce in Turkey’ Practical Hydroponics and Greenhouses. September/October, 56-59.
Flowerdew, B. (2002) Go Organic! London: Octopus Publishing Group Limited
Growing Media Association (2003) DEFRA Seminar April 2003- Alan Shaw [www document]. www.growingmedia.co.uk/industry1.html (accessed 2 January 2006)
Gunn, S. (2004) ‘Turning Composted Materials into Reliable Growing Media’ The Commercial Greenhouse Grower. February 20-22
Holmes, S. (2004) Peat and Peat Alternatives: Their use in Commercial Horticulture in England and Wales in 2003. England: Department for Environment, Food and Rural Affairs.
Keursten, R. (2005) ‘Cocopeat’s Versatility Suits Pots and Cut Flowers’ Flowertech Vol 8/No 7. 38-39.
Large, J. (1972) Glasshouse Lettuce: Grower Manual. London: Grower Books
Lennard, W (2005) ‘Aquaponics Simplified’. Practical Hydroponics & Greenhouses, July/August: 27-29
Peatering Out, (2005) 15 Good Reasons for Using Green Compost in Growing Media [www document] www.peateringout.co/info.html (accessed 25 October 2005)
Pizano, M. and Lorenzo, G.C. (2001) 34th Meeting of the Executive Committee of the Multilateral Fund for the Implementation of the Montreal Protocol. Uganda: UNIDO.
Remade Essex, (2005) Growing Media Trials [www document]. www.remadeessex.org.uk/pageDetail.asp?articleID=71 (accessed 2 January 2006)
Shabot, B. (2005) ‘Potted Campanula’ Grower Talks, November: 30-32
Appendix
Organic, peat-free sowing and potting composts
Source: Flowerdew (2002)