1. INTRODUCTION



1.1 Purpose

The purpose of this project is to investigate the effects on germination of seed by using ...
•   Nitrogen blocking?

   •   Capping?

   •   Stunted growth?

   •   Discolouration?

   •   What is the cost?

   •   ...
1.5 Usefulness

This experiment will help validate results from previous trials and give better information on

the effect...
2. LITERARY REVIEW

                     Chapter 2.1 Properties of Peat and its Alternatives

2.1.1 Peat

Peat is a non-re...
2.1.1.2 Chemical Properties of Peat

The Cation Exchange Capacity (CEC) of peat varies with its pH level. It is low in min...
2.1.2.1 Physical Properties of Coir

One of coir’s greatest advantages is its drainage qualities and low bulk density. But...
Neem tree seeds are a recent addition to growing media products, especially coir. Reiley and

Shry (2000) found that crush...
2.1.3.2 Chemical properties Of Peat Reduced Product (Loam Based)

With the reduced peat’s loam based content it has excell...
2.2.1 Background

Peat is a finite, non-renewable resource taking thousands of years to form. Although its use in

horticu...
2.2.3 Previous Germination Trials Using Peat Free Products

Horticulturalists, nursery stock growers in particular, are re...
of peat. Also with peat extraction being banned in the U.K., reliance on peat imports will

increase the price of the prod...
Seeds can remain dormant for several (and some in cases thousands of) years until all 3 of

these factors are present and ...
than loam or peat, yet problems with proper management may lead to over watering and

rotting of the seed.



2.3.1.3 Oxyg...
calcium, magnesium and sulphur would be sufficient (Mauseth, 2003). Appropriate levels,

for example 80-160 cmol Kg-1,of C...
with the media’s buffering capacity. With all three of the growing media selected for study

for their effect on germinati...
optimum of a different growing media in each environment, the reason being to find out how

different each growing media m...
(iii) Annual Rye Grass

Used in most domestic lawns for its fast growth and qualities of suppressing weeds. Annual

Rye Gr...
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Literature Review: An Investigation into the effects on seed germination using Reduced Peat & Peat Free growing media in comparison to Full Peat Growing Media

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An Investigation Into the Effects on Seed Germination Using Reduced Peat & Peat Free Growing Media in Comparison to Full Peat Growing Media

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Literature Review: An Investigation into the effects on seed germination using Reduced Peat & Peat Free growing media in comparison to Full Peat Growing Media

  1. 1. 1. INTRODUCTION 1.1 Purpose The purpose of this project is to investigate the effects on germination of seed by using peat alternative and peat reduced product and compare the results against those obtained from a 100% peat growing medium. This study also aims to find out whether peat alternative and peat reduced products are either inferior or superior to standard peat products. I will also study the differences between the growing media used in the germination trial. This study will investigate if there are cases of nutrient uptake problems, capping, stunted growth, discolouration, pH imbalance and slower germination rates. 1.2 Justification The subject of peat alternative and peat reduced products is a very important topic to study for the fact that peat is a non-renewable resource. Today we live in a “Green” political environment, with eco-friendly projects and products being pushed to the top of the public’s and politician’s agendas. The public are being openly encouraged to use peat-free and reduced peat products. But, strong criticism has been raised against peat-free products, claiming that they are ineffective, problematic and costly. This study aims to identify the problems, if any, and compare the products to the performance of one hundred per cent peat. 1.3 Questions The issues to be studied from this project are problems associated with peat alternatives and reduced peat products including: • What are the germination requirements of growing media? • What are the properties of peat, reduced peat and peat-free growing media? • Nutrient uptake? 1
  2. 2. • Nitrogen blocking? • Capping? • Stunted growth? • Discolouration? • What is the cost? • Why is their a reluctance of nursery stock growers to use peat alternatives? These problems can be addressed by adding fertiliser and nutrients but require more attention and time. Other questions to be addressed from this study is the effectiveness of one peat alternative, coir, which in some trials has out performed traditional peat. Solutions to these questions and problems will also be looked at, including their affordability and viability. 1.4 Method During the study of this topic I will be conducting an experiment on germination trials using a peat alternative product and a peat reduced product, using a one hundred percent peat product as a control. I will be using a coir based peat alternative (Gneem coir). Due to its high water retention qualities and recorded success rate it is a strong contender to full peat products. For the reduced peat product I will be using “John Inne’s seeding compost”. I will also be using “Shamrock seeding and potting compost”. I intend to do germination trials using four different plants. I will set up twelve seeding trays, with each plant seeded in each one of the different growing media products. I will be observing each one of the trays and recording details of when each tray germinates, strength of the seedling, colour and look for evidence of capping or stunted growth. I will then be comparing results between each of the trays and products. Also I will compare the results to previously recorded trials and data I have researched. I will also be sourcing information from books and scientific papers on subjects such as growing media, botany, germination and nutrient absorption. 2
  3. 3. 1.5 Usefulness This experiment will help validate results from previous trials and give better information on the effectiveness and problems of peat alternatives and peat free products. It will also replicate other studies and experiments using peat free products. It will also show that different composts work for different plants and may explain why peat alternatives and peat reduced products are reported as being failures as well as why they are stigmatised by the public and some nursery stock growers in particular. 3
  4. 4. 2. LITERARY REVIEW Chapter 2.1 Properties of Peat and its Alternatives 2.1.1 Peat Peat is a non-renewable resource, that is sourced from low lying bog land. It was formed from the accumulation of organic debris over thousands of years (Allaby, 2005). But because of the prolific scale of peat extraction many peat and wetlands have been destroyed (Hall and Pilcher, 2001). Peat was first introduced to commercial horticulture in the 1930’s to Europe and was chosen for use in compost mixes because of its light weight and its high water retention properties (Bragg, 2002). It is easy to see in the following sub-sections below why, because of peat’s physical and chemical composition, horticulturalists favour peat’s use as a growing medium over unproven or inferior alternatives. These properties also indicate why peat excavation and extraction has occurred on such a massive and profitable scale. 2.1.1.1 Physical Properties of Peat Peat main physical properties are its high air porosity, low bulk density and high water retention qualities. An example of its water retention properties before being cut, according to Flora Hibernica, is “Peat is at least 95 per cent water”. Its air filled porosity attribute is important for good air flow to be present and also to allow good root penetration in the soil (Wheeler and Wheeler, 2001). It is also used as mulch and a soil improver, because of its physical structure, at the cost of reducing the pH of the soil (Fedor, 2001). Physical properties such as these would allow easy root penetration and good root anchorage. Also with its air porosity levels, oxygen and water are readily available to the seed to ensure successful germination. 4
  5. 5. 2.1.1.2 Chemical Properties of Peat The Cation Exchange Capacity (CEC) of peat varies with its pH level. It is low in minerals and the addition of lime is required to raise soil pH as it is very acidic (Fedor, 2001). Peat’s fertility level is relatively low requiring the addition of nutrients and it is also very difficult to re-wet if it becomes too dry (Flowerdew, 2002). Peat is also a sterile source of growing media that inhibits pathogens dangerous to plants (Raviv and Heinrich Lieth, 2007). But because of peat’s low level of nutrients and pH it can be amended to suit the growers need with the addition of fertiliser and lime. This gives peat, as a growing medium, a wide range of applications for plants. 2.1.2 Peat Free Alternative – Coir Coir is a waste by-product (lingo-cellulose) made from coconut husks. It has a dusty appearance and looks quite similar to peat (Bragg, 2002). It is usually sold in dehydrated five litre packaged blocks that, when mixed with 35 litres water, makes 80 litres of growing media, according to Rossenarra nurseries. Coir has been used in horticulture since the Victorian era, but has faced problems such as sterile media and quality differing from source to source. Since the late 1980’s however, according to Raviv and Heinrich Leith (2007), it has re-emerged being used as a component of growing mix or simply as a growing medium itself. Modern environmentalists are against the import of coir as it is needed for agricultural and horticulture practices in their home country (Fedor, 2001). Another advantage is that coir costs considerably less than peat, but the fact that it has to be imported from areas such as Sri Lanka raises cost and carbon miles, therefore defeating coir’s “green” or environmentally friendly image. 5
  6. 6. 2.1.2.1 Physical Properties of Coir One of coir’s greatest advantages is its drainage qualities and low bulk density. But, coir is very easily over watered, because the surface appears dry, yet has sufficient water content present due to its water retention properties (Flowerdew, 2001). This can cause nutrients to be washed out if not managed properly. According to Raviv and Heinrich Leith (2007) Coir is usually composted for 6 months to give it a stable structure similar to that of peat. Coir also posses a higher percentage of air filled porosity than peat itself (Prasad and Ni Chualain, 2004). Rossenarra Gardener, the sole proprietor of “GreeNeem Coir Compost” in Ireland claims that their coir based product has water retention properties up to 700%. 2.1.2.2 Chemical Properties of Coir Coir has very low levels of nutrients present, except for noticeable levels of sodium, potassium and chlorine. As shown by Raviv and Heinrich Leith (2007), these nutrients may be present in toxic amounts and must be leached before being composted. Also problems with nitrogen being made available to the seed/plant due the occurrence of nitrogen locking, also the fact it lacks the capacity to hold onto nutrients (CEC) has lead to growers being reluctant to using coir (Bragg, 2002). Another problematic factor is huge differences in quality between sources of coir. This can lead to some products of coir containing high levels of salt causing toxicity in plants. Problems associated with CEC and nitrogen can easily be solved by the addition of clay minerals and nitrogen feed. Coir’s pH level falls somewhere between 5 and 6, depending on its source (Adams and Early, 2004). Coir can be problematic as a peat alternative as leaching is required before use and also testing would be required to ensure no pathogens are present as, unlike peat, coir is not sterile. This could have a serious effect on germination. The addition of Neem tree seeds however can solve this problem. 6
  7. 7. Neem tree seeds are a recent addition to growing media products, especially coir. Reiley and Shry (2000) found that crushed neem tree seeds contain the chemical azadirachtin which, inhibits pathogens, halts larvae development, and repels up to 170 damaging insects. It also acts as a nematicide and organic fertiliser. It gets absorbed into the plant systematically and acts as a shield of protection against pests. Another positive aspect is that it is non-toxic to humans. 2.1.3 Peat Reduced Product (Loam Based) Peat reduced products are a recent compromise to satisfy calls for a halt to the use of peat and also to find a viable peat alternative that has sustainable results. Peat reduced products are a stepping stone until the problematic issues associated with peat-free products are solved. The loam content of these products can vary, but ideally would be 20% silt, 20% clay and 60% sand (Fedor, 2001). 2.1.3.1 Physical Properties of Peat reduced Product (Loam Based) The peat reduced product being used in the experiment for this thesis contains 50% sphagnum moss peat and 50% loam. With their loam content these products also have higher water retention properties then full peat products and are quick to drain (Fedor, 2001). This water holding attribute is important, especially since water charges have been introduced. Loam also requires very little additives because of its low, yet sufficient clay content, along with the fact it has a high level of organic matter (Flowerdew, 2002). Its water retention would mean less water wastage, compared to peat. Also loam based peat reduced products are easier to re- wet than full peat because of their lower peat content and higher moisture absorption levels due to its loam content. 7
  8. 8. 2.1.3.2 Chemical properties Of Peat Reduced Product (Loam Based) With the reduced peat’s loam based content it has excellent C.E.C. attributes and also has sufficient organic content present in the loam. Because of these assets loam based reduced peat requires little or no fertiliser or feed (Fedor, 2001). Loam based reduced peat has similar chemical properties to 100% peat but with loam’s composition present it does not require lime to raise pH. 2.1.4 Comparison of Properties of Peat and Coir 2.1.4.1 Physical Properties of Coir and Peat Material Dry Weight g/L % Water Holding % Air Filled Capacity Porosity Coir 90 52 15 Sphagnum Peat 100 48 25 (Cresswell, 1992) 2.1.4.2 Chemical Properties of Coir and Peat Material Moisture % pH N %DWt P %DWt K %DWt Coir 13 5.1 0.5 0.3 0.4 Sphagnum Peat 9 3.3 0.9 0.5 0.1 DWt = Dry Weight N= Nitrogen P= Phosphorous K= Potassium (Cresswell, 1992) Chapter 2.2 Should Peat-Free Products Replace Peat? 8
  9. 9. 2.2.1 Background Peat is a finite, non-renewable resource taking thousands of years to form. Although its use in horticulture is not solely to blame for dwindling resources, peat reserves have been lost due to natural factors, building and also its use as an energy source (Bragg, 2003). There are massive reserves of peat on a worldwide scale, especially in the Baltic countries, but they are immature with different chemical and physical properties to peat used in Ireland and Britain. Yet another factor to encourage the use of peat alternatives is the destruction of low lying bog land environments for peat extraction. Yet, peat extraction has a huge turnover for business. For example, according to the Bord na Mona 2007/2008 annual report (2008), in the last year Bord na Mona has made a turnover of 371.2 million euro. 2.2.2 Damage to Peat and Wetlands Only 6% of Britain’s original lowland peat bogs remain, of which, only up to 5,000Ha is still in good condition (RHS (Royal Horticultural Society), 2008). Low lying raised bogs are a diverse habitat of plants and animals that have adapted to that environment. As mentioned by Professor Valerie Hall, speaking at the Botanical Gardens, Dublin, 2008, irreversible damage has been done to some bog land habitats, as invasive alien species of plants are now thriving on peat lands where the upper surface of the peat have been cut. According to Flora Hibernica (Hall and Pilcher, 2001) , 92 per cent of bog lands have been destroyed in Ireland and that, the remaining intact 8 per cent makes up 51 per cent of all bog land remaining in Europe. Some bogs are also archaeological sites with many precious treasures from the past buried there. 9
  10. 10. 2.2.3 Previous Germination Trials Using Peat Free Products Horticulturalists, nursery stock growers in particular, are reluctant to use inferior or unproven alternatives with little or no track record. Peat’s properties are highly unique and hard to replicate and compete against. Past problems, as shown in trials conducted by the RHS at Wisley gardens (Pickering, The Garden, September, 2000), including nutrient deficiencies, scorching, toxicities and contamination of growing medium with weed seeds and pathogens, occurring with alternatives have stigmatised them in the horticultural sector. The review of peat free composts published by GardeningWhich? (January 11, 2008) found that they faired poorly when compared to peat and recommended gardeners not to buy peat free composts. It is worth noting however, that GardeningWhich? didn’t include coir in that compost trial. This makes their conclusion, that peat free composts are currently inefficient unfounded, as they have not tested coir, a widely commercially available product. The trial conducted by the RHS gardens at Wisley (Pickering, The Garden, September, 2000) on the other hand, showed that “Fertile Fibre”, a peat free product composed mainly of coir, preformed comparably well to peat based products on seed germination. Although, it did record incidences of capping occurring with the coir based product, this was, however, also present in the peat based composts used in the trial. A lack of the number of trials proving conclusive evidence on peat free alternatives on seed germination has left the majority of horticulturalists uninformed and sceptical of peat free growing media. 2.2.4 Change Peat extraction is to be banned in the U.K. by 2012 (1997 Biodiversity Action Plan)(RHS Hampton Court Palace Flower Show Catalogue, 2006) and a number of organisations such as the National Trust and the Royal Horticultural Society (RHS) are pushing the public to be 90% peat free by 2010 (Holmes, 2007). In fact the RHS bans the use of peat at its flower shows. Many peat lands are now protected further restricting harvesting and raising the cost 10
  11. 11. of peat. Also with peat extraction being banned in the U.K., reliance on peat imports will increase the price of the product if no viable alternatives are marketed and supported accordingly. However due to Corporate Social Responsibility programmes on peat reduction, many retailers are now giving customers better choice of peat alternatives. But, as the following bar chart (Fig. 2.2.4.1) demonstrates, the level of peat use in the UK has not dropped, but shows the amount of peat alternatives being used is slowly on the rise. This also indicates that targets set for 2010 and 2012 will not be met. T otal Us e of P eat and Alternatives in the UK 1999-2005 4 C ubic Metres 3 (Million) P eat 2 Alte rnativ e s 1 0 1999 2001 2005 Y ear Figure. 2.2.4.1: Total use of peat and alternatives in the UK (Holmes, 2007). Chapter 2.3 Seed Germination 2.3.1. Seed Germination Requirements Germination of seeds, for the most part require only 3 very simple, yet absolutely necessary environmental factors. They are: • Water Availability • Temperature • Oxygen 11
  12. 12. Seeds can remain dormant for several (and some in cases thousands of) years until all 3 of these factors are present and sufficient for germination to occur. According to Success with Seeds (Wheeler and Wheeler, 2001), for seed germination to be successful the growing media used must have good drainage along with sufficient water retention. The pores of the growing media must also allow the physical transportation of water and air through the structure and allow roots to penetrate the growing media. 2.3.1.1 Temperature One of the most influential factors of germination, temperature is a primary catalyst. It is a key adaption by the plant/seed for survival. Without optimum temperature requirements, the seed will not begin moisture absorption; this is to prevent damage to or rupturing of cells from frost (Capon, 2004). Low temperature can even act as away of prolonging dormancy and proves an effective method of storing seed. Optimum temperature is the factor that kick starts the germination process. 2.3.1.2. Water Availability Water availability in the soil is vital for germination. Free draining soils with fine particles and poor water holding capacity e.g. sand, can loose water rapidly making germination unlikely/delayed. But the other extreme, a soil with micro-pores e.g. clay can make water absorption (availability) near impossible because of clay soils negatively charged particles (Wheeler and Wheeler, 2001). With water readily available to the seed, the process of imbibition takes place. Water is absorbed into the cell wall of the seed in between proteins and cellulose. This then leads to the components of the cell to swell and the outer wall softening. The seed components in fact double in size leading to the soft outer coat splitting (Capon, 2004). The three growing media being used in the experiment of this thesis have different water holding capacities. For example Coir has higher water retention properties 12
  13. 13. than loam or peat, yet problems with proper management may lead to over watering and rotting of the seed. 2.3.1.3 Oxygen Oxygen is a vital, necessary factor for seed germination. The growing media needs to be loose for an adequate level of oxygen to exist in the soil atmosphere, so that it can be consumed by the seed. Oxygen enters the seed by the process of diffusion. Oxygen is essential for cellular respiration to take place, where the food molecules are broken down into amino acids and sugars (Capon, 2004). These are then used, once transported to the embryo, to construct new cells to continue germination and for future growth. 2.3.2. Growing Media Requirements for Germination It was found by Reiley and Shry (2000), that an ideal growing medium for seed germination is one that is free of pathogens, pests and weeds, has an acceptable amount of available nutrients, with good porosity and posses a pH level required by the seed to be sown. Seeds require several factors to be present in growing media for successful germination to occur. The growing media should needs to have good porosity to allow root penetration to take place. Porosity is also important for oxygen to diffuse sufficiently in the medium so it is available to the seed (Capon, 2004). The medium must have good water retention qualities for growth to occur, but also sufficient drainage to prevent rotting of the seed and the growing media becoming waterlogged. Structurally, the growing media must be stable to prevent damage when waterlogged and also cannot be susceptible to being blown away by wind (capping). Ease of re-wetting would also be a factor in case of drought. The pH requirement of the medium depends on the plant, but if needed, lime or other feeds can be added, as in the case of peat, to increase pH (Raviv and Heinrich Lieth, 2007). Seeds tend not to use or require many nutrients for germination but suitable levels of nitrogen, potassium, phosphorus, 13
  14. 14. calcium, magnesium and sulphur would be sufficient (Mauseth, 2003). Appropriate levels, for example 80-160 cmol Kg-1,of Cation Exchange Capacity (C.E.C) would be necessary so that nutrients are not leached from the soil and are readily available to the plant. 3. Summary and Conclusions In this section I will state the information that I have learned and researched to establish my background knowledge of peat, reduced peat, peat alternatives and their effects on seed germination. Peat has long been established as the number one choice of gardeners for growing medium for the better part of a century. With its impressive track record, physical and chemical properties, horticulturalists, amateur gardeners and nursery stock growers are wary to try unproven methods and media. Trials carried out on reduced peat products and peat free products in the past that reported terrible results, compared to peat, furthered scepticism of reduced peat and peat-free growing media. But with mounting pressure to reduce the use of peat, a finite resource, environmentally minded growers have gone to great lengths to champion peat alternatives. Conservation laws, ecological damage to specialised habitats and UK government deadlines of halting peat extraction by 2012 gave further reason to pursue alternatives and refine problems of past peat- free media. Various trials, such as the RHS at Wisley have proven comparable results to peat with the use of coir, a peat-free growing medium by-product of coconut husks. Studies on the physical and chemical properties of coir have shown that it has better water retention abilities, higher air porosity and better drainage than peat. Also, amendments to reduced peat products, a product comprised with 50% peat to install confidence in the customer of its capabilities, acted as a stepping stone to peat free products. Possessing much of the same chemical properties as peat, but has less feeding requirements, for example, the addition of lime to raise pH. With additions of loam, levels of drainage qualities and organic matter increase along 14
  15. 15. with the media’s buffering capacity. With all three of the growing media selected for study for their effect on germination for this thesis, it was clear that each had its advantages and drawbacks. Peat for instance is hard to re-wet when dry and coir mean while, is very easy to overwater due to its high capillary action and moisture retentiveness. Further, I have learnt that there is a severe lack of conclusive evidence comparing peat, peat reduced, and peat alternative products, along with their effects on germination, to each other. Further conclusive testing over a broad range of seeds is needed to address the viability of peat free/peat reduced growing media and identify the problems, if any, of these growing media and possible solutions to these problems. 4. Outline of Research Proposal For my project implementation I plan to answer a number of questions and concerns about peat, reduced peat and peat free growing media. I will also interview nursery stock growers and amateur gardeners on their attitudes to using peat, reduced peat and peat-free products. I will attempt to discover the flaws and attributes of each growing media using a specific product from each category in a seed germination trial. The experiment is a version of germination trials carried out by the RHS and GardeningWhich? Magazine. It has some modifications to it, such as different plant seeds and controlled watering levels depending on the set up of specific optimum envoirments. The layout of the germination trial is as follows: The germination trial will be carried out in one of the glasshouses at Kildalton College, Piltown, Co. Kilkenny. It consists of three different growing media products: full peat, coir (peat alternative) and reduced peat (loam based/sphagnum moss). Three different species of seed (lettuce, annual rye grass and wallflower) will be sown in each one of the growing media. Three different environments will be established. Each one will be operated to the 15
  16. 16. optimum of a different growing media in each environment, the reason being to find out how different each growing media must be treated for successful germination. E.g. Coir (peat alternative) optimum environment needs very little water, may cause unsuccessful/poor germination in full peat tray. Nine trays in all will be sown with the different species of seed, with the seeds being arranged in different orders to prevent variations in the results due to outbreak of disease and/or pest damage. I will inspect the experiment twice a week to water the trays and inspect/record germination progress. Measurement of pH, air filled porosity and amount of nutrients will be recorded of the soil growing media before and after germination. Also root growth, penetration and anchorage in the growing medium will be investigated and recorded. I will be comparing the results of this germination trial to previous germination trials using peat, reduced peat and peat alternatives. I will start the project on 24th October 2008. I expect the trial to be completed in the last week of November. Information on Seeds to be Germinated (i) Wallflower “My Fair Lady”/ Cherianthus cheiri “My Fair Lady” Wallflower “My Fair Lady” is a hardy biennial usually sown in early summer. They will grow in most soils and survive in part shade/full sun. It is required to keep the soil damp until germination. (ii) Lettuce “Lakeland” Lettuce “Lakeland” is usually sown from March to July and is harvested from June to October. The plant usually germinates in 7-14 days. It requires a moisture retentive yet free draining soil. 16
  17. 17. (iii) Annual Rye Grass Used in most domestic lawns for its fast growth and qualities of suppressing weeds. Annual Rye Grass requires very little resources for successful germination. Sufficient water and nutrients will ensure strong germination. 17

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