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Quality of peat moss as a component of growing media Mofidpoor, Maryam 2007

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Q U A L I T Y O F P E A T M O S S A S A C O M P O N E N T O F G R O W I N G M E D I A by M a r y a m Mofidpoor B.Sc. Soil Science, Ferdowsi University, Mashhad, Iran, 1998 A thesis submitted in partial fulfillment of the requirements for the degree of M A S T E R OF S C I E N C E in T H E F A C U L T Y O F G R A D U A T E S T U D I E S (Soil Science) T H E U N I V E R S I T Y OF B R I T I S H C O L U M B I A June 2007 ©Maryam Mofidpoor, 2007 Abstract Quality of growing media is crucial for plant health and growth in nurseries and green houses. The objective of this study was to determine the effect of peat moss source and length of storage time on the quality of peat moss. Nine bales of peat moss collected from upper, less decomposed layer of a bog near lake Winnipeg in Manitoba and nine bales of peat moss excavated from lower, more decomposed layer of a bog near Vilna, Alberta were sampled after one, three, and 10 months of storage. The Manitoba peat moss had larger particle size, greater gravimetric water content, and greater NH4-N content relative to the peat moss from Alberta. The Alberta peat moss had higher pH, EC, and N03-N content. Plant available water content was the same in both peat moss. Particle size was decreased at 10 months storage time in both peat moss (based on wet sieving method), NH4-N content was reduced at 10 months in the Manitoba peat moss, N03-N was increased at three months in the Alberta peat moss, and EC was increased at three months in both peat moss. The result of this study suggested that the growing media industry should store peat moss for less than 10 months and the available N should be monitored on a regular basis. n Table of Contents Abstract . • ii Table of Contents . iii List of Tables v List of Figures viii List of Photos.... ix Co-authorship Statement x Acknowledgments xi 1. GENERAL INTRODUCTION 1 1.1. Scope of the Growing Media Industry 1 1.2. Most Common Ingredients of Growing Media Mixes 1 1.3. Factors Affecting the Quality of Peat Moss 4 1.4. Quality Indicators 7 1.5. Study Objectives 12 1.6. References 13 2. QUALITY OF MEDIUM GRADE PEAT MOSS AS A COMPONENT OF GROWING MEDIA 19 2.1. Introduction ; 19 2.2. Materials and Methods 21 2.2.1. Site description 21 2.2.2. Sampling 23 2.2.3. Laboratory Analysis 24 2.2.4. Statistical Analysis 30 2.3. Results and Discussion 31 2.3.1. Site Conditions 31 2.3.2. Size Distribution of Organic Particles Determined by the Dry Sieving Method 33 2.3.3. Size Distribution of Organic Particles Determined by the Wet Sieving Method 37 2.3.4. Gravimetric Water Content .....40 2.3.5. Plant Available Water 41 2.3.6. Chemical Properties .43 2.3.7. Odor '. .48 2.3.8. Content of Weeds .....48 2.4. Conclusions 48 3. R E C O M M E N D A T I O N S F O R F U T U R E S T U D I E S 54 Appendix A 55 Appendix B 66 List of Tables T a b l e 1.1. Percentage of organic particles passing the corresponding sieve size for medium and fine grades of peat moss 7 T a b l e 2.1. Total elements (mg kg"1) and average ash content (g 100 g"1) of peat moss harvested from a bog in Manitoba and a bog in Alberta : 32 T a b l e 2.2. Gravimetric soil water content of Alberta and Manitoba medium grade peat moss 41 T a b l e 2.3. Plant available water of Alberta and Manitoba medium grade peat moss stored for one and 10 months 43 T a b l e 2.4. Soil p H , electrical conductivity (EC), and N H 4 - N content of Alberta and Manitoba medium grade peat moss 45 T a b l e 2.5. Nitrate-N content of Manitoba medium grade peat moss 47 T a b l e 2.6. Nitrate-N content of Alberta medium grade peat moss 47 T a b l e A.l. Analysis of variance for the effect of storage time on 0.6 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method 55 T a b l e A.2. Analysis of variance for the effect of storage time on 1.18 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method '. 55 T a b l e A.3. Analysis o f variance for the effect o f storage time on 2.36 mm size fraction o f medium grade peat moss from Manitoba and Alberta determined by dry sieving method 56 v T a b l e A .4 . Analysis of variance for the effect of storage time on 4.75 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method 56 T a b l e A . 5 . Analysis of variance for the effect of storage time on 6.35 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method 56 T a b l e A .6 . Analysis of variance for the effect of storage time on 9.5 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method 57 T a b l e A . 7 . Analysis of variance for the effect of storage time on 0.15 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by wet sieving method •. 57 T a b l e A .8. Analysis of variance for the effect of storage time on 0.4 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by wet sieving method 58 T a b l e A . 9 . Analysis of variance for the effect of storage time on 1 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by wet sieving method 58 T a b l e A . 10. Plant available water in medium grade Manitoba peat moss stored in bales for one, three, and 10 months...- 59 T a b l e A.11. Plant available water in medium grade Alberta peat moss stored in bales for one, three, and 10 months 60 vi Table A.12. Odor determined at one, three, and 10 months of storage time in Manitoba peat moss 61 Table A.13. Odor determined at one, three, and 10 months of storage time in Alberta peat moss 62 Table A.14. Number of weed seeds germinated per 60x25 cm tray in Manitoba and Alberta peat moss .' 63 Table A.15. Water content (cm 3 cm "3) at 0.002, 0.01, and 0.05 M P a at one, three, and 10 months storage time in Manitoba medium grade peat moss 64 Table A.16. Water content (cm 3 cm "3) at 0.002, 0.01, and 0.05 M P a at one, three, and 10 months storage time in Alberta medium grade peat moss 65 vii List of Figures Figure 2.1. Percent of organic particles (determined by dry sieving method) of Manitoba and Alberta medium grade peat moss passing each sieve size at (a) one, (b) three, and (c) 10 months storage time 34 Figure 2.2. Percent of organic particles (determined by dry sieving method) o f Manitoba medium grade peat moss (a) and Alberta medium grade peat moss (b) passing each sieve at one, three, and 10 months of storage time 36 Figure 2.3. Percent o f organic particles (determined by wet sieving method) o f Manitoba and Alberta medium grade peat moss passing each sieve size at (a) one, (b) three, and (c) 10 months storage time 38 Figure 2.4. Percent o f organic particles (determined by wet sieving method) o f medium grade peat moss harvested from the Manitoba bog (a) and Alberta bog (b) passing each sieve at one, three, and 10 months of storage time, 39 Figure B . l . Comparison o f wet sieving method (1 mm particle size) and dry sieving method (1.18 mm particle size) 66 Figure B .2 . Water content determined at 0.002, 0.01, and 0.05 M P a of Manitoba and Alberta medium grade peat moss that were stored for one (a), three (b), and 10 months (c) 67 vi i i List of Photos Photo 1. Trenches were installed as part of the bog preparation for harvesting 23 Photo 2. Vacuum harvesting machine 23 Photo 3. Processing of the peat moss 23 Photo 4. Baling of the peat moss 23 Photo 5. Each individual sieve was sealed with a rubber band 26 Photo 6. Stack of sieves was secured with clamps and rubber bands 26 Photo 7. The bucket connected to the air tap 26 Photo 8. Top container with a plug in the bottom hole and a second container for solution collection 29 Photo 9. Peat moss sample in the container prior to saturation 29 Photo 10. Saturated paste of a peat moss sample 29 ix Co-authorship Statement Chapter 2: I was responsible for the experimental design, data collection, all statistical analyses, and writing the manuscript. Maja Krz ic contributed to the experimental design, the choice of statistical tests and to the interpretation and presentation of the manuscript. Laura Principe contributed to the selection of sample size and selection of laboratory methods. j x Acknowledgments I would like to thank everyone who has offered their immense technical and spiritual support, throughout my study. I am very grateful for the guidance, patience and countless redirections of my supervisor, Dr. Maja Krz ic my committee members, Dr. Les Lavkulich and Dr. Art Bomke during this journey. I also would like to thank Dr. Andy Black for the great recommendations and redirection about the last minute crisis of my study. Laura Principe as my supervisor from industrial collaborator of the study ("West Creek Farms" Fort Langley, B C ) has offered a lot of help, recommendations, support and time for the past three years and I thank her profoundly for all of that. I also would like to thank Dr. Tony Kozak for guiding me through the statistical maze for this study. I am grateful for my attendance at the University of British Columbia for all the precious experiences and great people that I met. I am thankful for being in the Faculty of Land and Food Systems for offering me a chance to adopt a new approach in problem solving. I would like to extend my thanks to my friends, Toktam Sajedi, Shannon Ripley, Beth Brockett, Julie Deslippe, and Denis Brooks for their strong supports throughout the hardest time in my life and keeping me sane, and Stephanie Grand, Simon (Yihai) Zhao, Brian Wallace, and Matt Ba l l for their technical support and scientific discussions that we had. This study was funded by the Natural Sciences and Engineering Research Council ( N S E R C ) of Canada and "West Creek Farms" company. x i 1. GENERAL INTRODUCTION 1.1. Scope of the Growing Media Industry Canada has about 111,328,000 ha of peat bogs that make up 25% of the world's peat (Hood, 1999) and provide about 98% of the sphagnum peat moss used in the United States (Sungro Horticulture Canada Ltd., 2004). Out of total land covered by peat bogs in Canada, peat moss is harvested from 0.014%. Harvesting is done by a limited number of private companies (Bergeron, 1996; Hood, 1999). The "Sphagnum Peat Moss Association", founded in 1988, consists of 18 peat moss producers and marketers that represent 95% of Canada's total production of peat moss (Sungro Horticulture Canada Ltd!, 2004). To protect bog development, harvesting licenses are issued only for bogs that have at least 2 m of high quality peat with minimum areal extension of 50 ha (Daigle and Daigle, 2001). Ornamental horticulture industry (greenhouse and nursery) in British Columbia (BC) was responsible for about $264 mil l ion or 18% of Canada's total ornamental and plant sales in 2005 (Statistics Canada, 2005). This industry provided 7,910 full- and part-time jobs in B C with a gross yearly payroll o f $115,854,000 (Statistics Canada, 2005). 1.2. Most Common Ingredients of Growing Media Mixes The quality of growing media used in the greenhouse and nursery industry is crucial to plant health. Plants in containers have only a small volume of media from which to satisfy air, water, and nutrition needs. Thus, the quality of the growing medium can be equated to its ability to supply plants with the optimal balance of air, water, and 1 nutrients. Good quality growing media aid in avoiding plant stress and thereby minimize susceptibility to opportunistic diseases and insects. Avoiding plant stress reduces fungicide and pesticide use and increases operation efficiency and product quality. Growing media mixes include ingredients such as bark, topsoil, sawdust, coir (coconut husk fiber), peanut hulls, perlite, vermiculite, peat moss, and various composts made from yard or sewage wastes. A growing medium could be composed of just one ingredient or a mix of ingredients, with or without soil. Key properties of some of the most commonly used ingredients are outlined below. a) Hardwood bark, of tree species such as pedunculate oak (Quercus robur L.) and copper beech (Fagus sylyatica L.) is usually higher in cellulose (up to 40%) than softwood bark (up to 5% cellulose). Softwood bark, of tree species such as Norwegian spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.) has higher phytotoxicity potential. On the other, hand hardwood bark has a greater capability to suppress some root infecting fungi and nematodes than softwood bark (Bunt etal., 1988). b) Sawdust is the byproduct of wood processing with p H between 5.5 and 6.5 (Ferry et al., 1998). It generally decomposes more rapidly than hardwood and softwood bark (Bunt et al., 1988). c) Coir is the binding material produced during the extraction of long fibers from the coconut husk. In order to be used in horticulture, coir is washed, screened, graded, and processed. Coir is characterized by uniform texture and high consistency that allow high water absorption. The growing media mixtures that contain coir can hold water up to 2 eight times relative to their own weight. Generally, coir has p H between 5.7 and 6.5 (GreeNeem Company, 2004) and cation exchange capacity (CEC) between 31.7 and 95.4-cmolc kg" 1 (Abad et al., 2002). Nutrient-holding capacity of coir is lower, while contents of Na , CI, P, and K are higher relative to peat moss (Ferry et al., 1998). d) Vermiculite is an A l - F e - M g silicate mineral During heating of vermiculite at 1000°C crystalline water is released leading to expansion of the mineral and increase of the surface area. Potting mixtures that contain vermiculite are characterized by high porosity. Vermiculite is also characterized by high nutrient and water holding capacity, and high level of K , Ca, and M g (Ferry et al., 1998). Vermiculite tends to be slightly to highly alkaline with p H ranging from 6.3 to 9.7, depending on its source (Koths and Adzima, 1971). Vermiculite is fragile and it easily breaks down with improper or excessive handling. It also can break down over time as a result of watering (Ferry et al., 1998). e) Perlite is an A l - S i mineral of a volcanic origin. Similar to vermiculite, the processing of perlite involves heating at 1000°C that leads to creation of expanded aggregates (Bunt et al., 1988). The perlite aggregates are white and very light. Perlite is used in growing mixes to enhance porosity. Its water holding capacity is lower relative to vermiculite (Ferry etal., 1998).. f) Peat moss, harvested from peat bogs, is the most commonly used ingredient of growing media in America and Europe (Hood, 1999). Generally, peat moss p H ranges from 3.0 to 6.0 and its E C is below 0.1 dS m" 1. Sphagnum peat moss contains 90 to 99% of organic matter and is characterized by high nutrient capacity and C E C (often between 110 and 130 cmol c kg"1) (Bunt et al., 1988; Ranneklev, 2003). 3 The high porosity of peat moss (about 74%), which is a result of its spongy structure, allows for high water absorption (Biglow et al., 2004). Consequently, a dry Sphagnum peat moss can absorb water up to nine times its weight. Moist Sphagnum peat moss readily absorbs water, but as the moss dries out, it tends to repel water. To rectify this problem, growing media companies usually add wetting agents to Sphagnum peat moss (Sungro Horticulture Canada Ltd., 2004). Peat moss has low bulk density (0.06 to 0.1 M g m"3), making it suitable for use in smaller containers. Peat moss can comprise 50 to 100% of the volume of the mixes in small containers, while in larger containers peat moss usually makes up to 25% of volume. In addition, low bulk density of peat moss allows the creation of relatively light mixes that can be handled and shipped at lower cost than mixes containing predominantly sand (Principe, personal communication, 2005). Peat moss is usually characterized by low numbers of plant pathogens and weed seeds, which diminishes the risk of introduction or dissemination of soil-based pests (Reedy, 2005). Consequently, there is no need for pretreatments (e.g., steaming) that might be necessary for other ingredients such as coir to meet weed seed content requirements of a growing medium (Van Schie, 1999). 1.3. Factors Affecting the Qual i ty of Peat Moss Peat moss is harvested from peat bogs in all provinces and territories of Canada, but the majority of peat moss used in the growing media industry in western Canada originates from bogs in Alberta and Manitoba (Principe, personal communication 2005). Factors such as peat origin and methods of harvesting and processing can affect the quality of peat moss. 4 a) Bog vegetation Peat is formed from various wetland plant species that include reedgrasses (Phragmites sp.), sedges (Carex sp.), and moss (Bunt et al., 1988). Wetlands or bogs, dominated by Sphagnum moss species are saturated with water during most of the year, while wetalnds dominated by the sedges are characterized by fluctuating water table and better decomposition (Tomassen et al., 2004). Peat harvested from moss-dominated bogs is generally characterized by higher water retention relative to peat from the sedge-dominated bogs (Bunt et al., 1988). This is the result of spongy structure of the peat moss (Paivanen, 1982). b) Depth of the harvested layers Generally, better quality of peat moss for the growing media industry is obtained from upper bog layers that are excavated in early stages of the bog exploitation. The upper bog layers are less decomposed and consequently more fibrous than lower bog layers (Visscher, 1988). When a new bog is brought under excavation, usually 75% of peat is of a high quality (i.e., less decomposed), while decomposed peat of lower quality comprises 25% of the total harvest (Sungro Horticulture Canada Ltd. , 2004)..Over the course of bog exploitation, peat is excavated from lower and lower layers, and at later stages of excavation the harvest load increasingly consists of a higher volume of older and more decomposed peat moss. c) Methods of harvesting and processing Quality of the sphagnum peat moss is also affected by methods of harvesting, processing (piling, screening, mixing, and crushing), and handling (Noble et al., 1999). Several studies have indicated that sod harvesting technique (peat excavation in lumps for 5 storage over the winter) produced coarser particles of a stable structure, while milled peat harvesting method (disk-harrowing the bog surface and ridging with a V-shaped windrower) produces finer (and less desirable) particles (Puustjarvi, 1983). d) Length of the storage time The European peat moss industry is concerned with the impact of the duration of the storage time on peat quality. European scientists believe that lack of oxygen may lead to some degree of denitrification in baled peat and raise in temperature might induce self heating, decomposition of organic matter resulting in particle size reduction, fungal growth, and probable production of toxic chemicals. In B C , growing media producers use peat moss that has been stored in bales for up to eight or 10 months. To my knowledge, no study has evaluated the impacts of the storage time on the baled peat moss quality. Shortcomings in growing media quality often go unnoticed until significant crop reduction occurs. A t that point it can be very difficult, costly, and even impossible to get the crop back on track. Increased Canada - U .S . border security, the introduction of new pests and diseases, and enhanced popularity of quality programs such as the International Organization for Standardization (Wever, 1995; de Kreij and Wever, 2005) have resulted in greater customer demand regarding quality control of growing media and documentation. In response to these demands and since there are no local standards for assessment of growing media quality, the "West Creek Farms", a potting soil company located in Fort Langley, B C (the industrial collaborator for this study), is trying to develop its own quality control program. There is very limited research in Canada on quality of peat moss as a growing media base and my study attempted to shed some light 6 on issues related to quality of this important component, commonly used in greenhouse and nursery industries. Growing media companies, generally, sort peat moss into several grades. For example, medium (or growers or regular) grade refers to the peat moss that is used for bedding and potting plants in large containers (diam. > 10 cm) (Table 1.1). Fine (or seedling) grade refers to the peat moss used in trays with 1.5 x 1.5 cm or 2 x 2 cm cell sizes. These trays are used for transplants and growing tree seedlings for the forestry industry. Table 1.1. Percentage of organic particles passing the corresponding sieve size for medium and fine grades of peat moss (Principe, personal communication, 2005). Percentage of particles passing sieve sizes Grade <9.5 mm <6.35mm <4.75 mm <2.36mm <1.18mm <0.6 mm Medium 96-98 89-93 81-88 73-76 57-61 35-40 Fine 94-100 88-99 85-97 77-90 68-77 44-54 1.4. Qual i ty Indicators Various soil quality indicators have been used to evaluate the quality of peat moss as a growing media used in greenhouse and nursery industry. These quality indicators are commonly analyzedin growing media companies and are selected based on the needs of growers. Some of these indicators are outlined below, a) Size distribution of organic particles Physical properties of peat moss in general and size distribution of its organic particles in particular, are of great importance for good quality of a growing media. Size 7 and arrangement of peat particles affects the pore size, gas exchange, and water storage (Boelter, 1969). A decrease in pore size could diminish air filled porosity, and in turn jeopardize plant growth and yield (Puustjarvi, 1983; Allaire et al., 1999). There is a disagreement on the size of the very fine particles that affects the air filled porosity. Based on "West Creek Farms" standards, the size fraction < 0.6 mm is referred to as dust fraction and it can obstruct macropores and lead to imperfect drainage through gravity. On the other hand, in some studies the attenuation of stored air is attributed to the increase of particles < 1 mm or 0.5 mm (Puustjarvi, 1976; Verdonk and Gabriel, 1988; Riviere, 1992). The presence of this very fine fraction is not desirable for the growing media industry (Principe, personal communication, 2005). In addition, the very fine dust fraction of peat may block the mixing equipment, causing complications during preparation of the peat-based growing media (Principe, personal communication, 2005). Another physical characteristic of peat moss that is commonly and closely monitored during organic particle size analysis is length and thickness o f sticks. Presence o f sticks is tolerated as long as they do not bridge the container (pot) or the cells of the trays. The stick size tolerance is 0.3 x 1.5 cm for fine peat fraction and 0.6 x 7 cm for medium peat fraction. b) Water retention Water retention is one of the quality indicators that is measured in "West Creek Farms" to evaluate plant available water in peat moss. De Boot and Verdonck (1972) suggested that the difference between water content at container capacity (water content at 0.001 M P a in peat moss (White, 1965)) and water content at 0.01 M P a is the volume of available water. Bigelow et al. (2004) referred to the difference of water retention 8 between 0.004 M P a and 0.05 M P a as the peat moss plant available water. Knowing water retention that corresponds to different pressures (the negative value of these air pressures corresponds to the soil water matric potential) allows growers to manipulate growth stage, flowering, or stem elongation (Morel et al., 1999), and facilitate the irrigation in green houses and nurseries (Caron and Riviere, 2003). c) Soil p H and salt content Lucas and Davis (1961) reported that the optimum p H values (as determined on the water suspension) of the Sphagnum peat moss and wood-sedge peat as growing media were 5.0 and 5.5-5.8, respectively. Since Sphagnum peat moss usually has p H between 3.5 and 4.5, liming is necessary to get to the optimum plant growth p H (Caron and Riviere, 2003). The p H of peat moss has an impact on the degree of decomposition. For example, Waksman and Stevens (1929) observed that highly acidic peat sites (pH was not specified) had a lower rate of decomposition, whereas less acidic sites (dominated by sedge and grass) had a higher decomposition rate of cellulose and hemicellulose and accumulation of lignin, and proteins. Peat moss is usually characterized by a low level of soluble salts (i.e., E C < 0.1 dS m"') (Gonzalez, 1981 and 1991), while other growing media ingredients such as coir may have higher E C . Therefore, to manage the level of salt and avoid the potential harmful effects of salts for plant growth, E C of all the ingredients of a mix should be monitored. d) Nitrogen content Nitrogen concentration of peat is strongly affected by the type of peat and in peat moss; it varies from 0.5 to 2% of total mass, while in sedge peat N-content ranges from 9 2.5 to 3.9% of the total mass (Davis and Lucas, 1959). Potila and.Sarjala (2004) reported a great fluctuation of the extractable N H 4 + and NO3", and dissolved organic N in peat during the growing season. The inorganic form of N composes a small fraction in organic soil; nevertheless some NO3" might be present in well-drained soils. Since the degree of decomposition was higher in sedge-grass peat relative to Sphagnum peat moss, Waksman and Stevens (1928) proposed that the decomposition of the plant proteins and the synthesis of microbial cell substances could lead to the accumulation of organic N complexes (the degree of decomposition was not specified). On the other hand, Gorham (1953) suggested that due to low level of microbial activity and the very low N content in Sphagnum, the N content is very low in Sphagnum bogs. Presence of the high levels of N H 4 - N in the growing media often is a cause of concern for growers. In addition to the ammonia-like odor, other problems in greenhouses have also been related to the high level of N H 4 - N . In cold and wet conditions, which might happen in nursery storage or in some cultivation methods, the chance of N H 4 accumulation increases. In 2005, a grower who plants tulips reported that in the delivered mix from the "West Creek Farms" a smell similar to ammonia was observed and growing of the bulbs in that mix was not successful (Principe, personal communication, 2005). The tulip's tolerance of N H 4 - N and N O 3 - N was reported to be 3 and 30 ppm, respectively. The pots of tulip bulbs are kept at 4-9° C to produce tulips in October and November (to delay flowering, tulips are kept in low temperature), which can cause the accumulation of N H 4 - N . The soil samples from the nursery have been tested and did not indicate any other problem rather than high level of N H 4 - N . The lab has reported that the high level of N H 4 - N in peat moss source might be an indication of increase in organic acid presence in peat moss, which created some 10 problem in root system development (Soil and Plant Lab Laboratory Inc., 2005). After observing these problems in greenhouses, I decided to monitor the level of N H 4 - N and N O 3 - N over time. e) Odor Although peat moss odor is harmless to people and plants, it still raises some concern. Smelly peat moss is the result of a phenomenon called "self-heating" and it occurs in stock-piled peat moss. Puustjarvi (1983) indicated that growers tend to predict the peat productivity attenuation through a certain smell of peat. This smell was associated with partial combustion in peat. Wi th increasing temperature, microbial activity in the peat pile intensifies and creates a heat pocket at the center of the peat moss heap. When the temperature rises to 29°C the thermophilic microorganisms become more active and generate more heat (Reddy, 2004). It is believed that self-heating changes physical and chemical characteristics of peat moss (Puustjarvi, 1983; Gardenas, 1984; Wever and Hertogh-Pon, 1993). In a study by Reddy (2004), self-heated peat moss was more water repellent and had greater concentrations of N H 4 - N , P, Ca, Fe, M g , and B , as well as overall salt content. Some of these changes can have negative impacts on seed germination, or growth of cuttings and small plants by producing toxic chemicals in the peat (Puustj arvi, 1983). A highly self-heated peat moss has lower p H and greater buffering capacity, which is undesirable for p H adjustments within growing media mixes (Reddy, 2004). f) Weed seed germination Weed control in the nursery industry is essential for marketable production of plants (Cross et al., 1992). Peat moss as an ingredient of the growing media may contain 11 weeds that reside in peat bogs. Application of peat moss that contains weed seeds in nursery and plant propagation operations causes several problems, including additional labor for removing weeds, competition for resources between main plant and weed, and hosting diseases and pests by weeds. In a study by Cross et al. (1992) counting weeds was used to ensure a good quality of sand and bark mixes in the nursery production. The sand and bark used in the study mentioned above had similar counts of weed seed. 1.5. Study Objectives The objective of this study was to assess the effects,of peat moss source and length of storage time on peat moss quality. Hypothesis tested were: (a) Peat moss harvested from a Sphagnum bog in Manitoba (in the early stage of exploitation) had higher quality than peat moss harvested from a Sphagnum bog in Alberta (in the later stage of exploitation) (b) Peat moss stored for one month in bales was of a higher quality than peat moss stored in bales for three and 10 months. The ornamental horticulture industry utilizes both medium and fine grade peat moss. In my thesis only results for the medium grade peat moss are presented. 12. 1.6. References Abad, M., Noguera, P., Puchades* R. ,Maquieira, A. and Noguera, V. 2002. Physico-chemical properties of some coconut coir dusts for use as a peat substitute for containerised ornamental plants. Bioresour. Technol. 82: 241-245. Allaire Leung, S.E., Caron, J., and Parent, L.E. 1999. Changes in physical properties of peat substrates during plant growth. Can. J. Soil Sci. 79: 137-139. Bergeron, M. 1996. Peat. [Online]. Available: http://www.nrcan.gc.ca/mms/cmy/content/1995/44.pdff31May 2007]. Bigelow, C , Bowman, D., and Cassel, D. 2004. Physical properties of three sand size classes amended with inorganic materials or sphagnum peat moss for putting green rootzones. Crop Sci. 44: 900-907. Boelter, D. 1969. Physical properties of peats as related to degree of decomposition. Soil Sci. Soc. A m . J. 33:606-609. Bos, E.J., Keijzer, R.A., Van Schie, W.L., Verhagen, J.B. and Zevenhoven, M. A. 2003. Growing media and Substrates. R H P Foundation Brochure. Naaldwijk. The Netherlands. Bunt, A.C, Hons, N.D.H. and Biol, M.I. 1988. Material for loamless mixes. Pages 6-39 in Media and mixes for container-grown plants. Unwin-Hyman Ltd. , London, U K . Caron, J. and Riviere, L.M. 2003. Quality of peat substrates for plants grown in 13 containers. Pages 67-91 in L . E . Parent and P. Ilnicki, eds. Organic soils, peat materials, sustainable agriculture. C R C Press, Florida, U S A . Cross, G.B. and Skroch,W.A. 1992. Quantification on weed seed contamination and weed development in container nurseries. J. Envir. Hort. 10:159-161. Davis, J.F., and Lucas, R.E. 1959. Organic soils, their formation, distribution, utilization and management. B u l l . 425. Michigan Stat Univ. Agric . Esptl. Sta. East Lansing, Michigan, U S A . De Boodt,M. and Verdonck,0. 1972. The physical properties o f the substrate in horticulture. Pages 37-44 in Proc. I l l Sym. on Peat in Horticulture. V o l . 26. Dublin, Ireland. de Kreij, C. and Wever, G. 2005. Proficiency testing of growing media, soil improvers, soils, and nutrient solutions. Commun. Soil Sci. Plant Anal . 36: 81-88. Daigle, J and Gautreau-Daigle, H. 2001. Canadain peat harvesting and the environment. North American Wetland Conservation Council Committee. Ottawa. Ferry, S.H., Adams, R., Jacques, D., Macelhannon, B., Schill, P. and Steinkamp, B. 1998. Soilless media: Practices make profit, [online] Available: http://www.scottsprohort.com/_documents/tech_articles/200307_PMP.pdf [31 M a y 2007]. Gardenas, S. and Thbrnqvist, T. 1984. Spontaneous combustion and dry matter losses in peat storage. Rep. N o 156. Department of Forest Products. The Swedish University of Agricultural Sciences. Uppsala, Sweden. Gonzalez, A. 1981. Br ief description of chemical and physico-chemical properties o f 14 peat material used in container raised crops in Quebec (in French). Rep. L A U - X - 4 8 , Laurentian Forestry Research center, Sainte-Foy, Quebec. Gonzalez, A. 1991. Effects of physical and physico-chemical properties of the substrate on growth of white spruce seedlings (in French). Proc. Sym. on peat and peatlands: Diversification and innovation. Quebec. Canadian Society o f peat and peatlands. Echo Bay. Ontario. Gorham, E. 1953. Chemical studies on the soils and vegetation of water logged habitats in the English Lake District. J. Ecol . 41: 345-360. GreeNeem Company. 2004. Coco coir peat, [online] Available: http://www.greeneem.com/cococoirpeat.htm [31 M a y 2007]. Hood, G. 1999. Canadian peat harvesting and its effect on the environment. Proc. Int. Sym. Growing media and Hydroponics. Windsor, Ontario. ISHS. The Netherlands. Koths, J.S. and Adzima, R. 1978. Domestic vs. African vermiculite for seedlings. Connecticut Greenhouse Newsletter 89: 1-7. Lucas, R.E. and Davis, J.F. 1961. Relationship between p H values i n organic soils and availabilities of 12 plant nutrients. Soil Sci. 92: 177-182 Martinez, F.X., Sepo, N. and Valero, J. 1996. Physical and physicochemical properties of peat moss-coir mixes and the effects of clay-material addition. Proc. Int. Sym. Growing media and hydroponics, Freising, Germany. ISHS, Leiden, The Netherlands. Noble, R., Doborvin-Pennington, A. Evered, C E . and Mead, A. 1999. Properties of peat-based casing soils and their influence on water relations and growth of mushroom(Agaricus bisporus). Plant and Soil 207: 1-13. 15 Paivanen, J. 1982. Ma in physical properties of peat soils. Peatlands and their utilization in Finland. Finnish peatland society, Helsinki, Finland. Potila, H. and Sarjala, T. 2004. Seasonal fluctuation in microbial biomass and activity along a natural nitrogen gradient in a drained peatland. Soil B i o l . Biochem. 36: 1047-1055. Puustjarvi, V. 1983. Effect of self-heating in stockpiles on the structure of horticultural peat. Pages 57-63 in Peat and plant yearbook. Association of Finish Peat Industries, Helsinki, Finland. Ranneklev, S.B. and Baath, E. 2003. Use of phospholipid fatty acids to detect previous self-heating events in stored peat moss. App l . Environ. Microbiol . 69: 3532-3539. Reedy, S. 2004. Self-heated peat. Floriculture International. January 2004. Reedy, S. 2005. Is peat helping you? Grower talks. March 2005. pp 32-34. Riviere, L.M. 1992. Water cycles of substrate-plant system in soilless culture (in French). Universite d'Angers, Ecole Nationale dTngenieurs des Travaux de l'Horticulture et du Paysage d'Angers, Angers, France, 141pp. Statistics Canada. 2005. Greenhouse, sod and nursery industries, [online]. 22-202-XIB: 1-28. Available: http://www.statcan.ca/english/freepub/22-202-XIB/0000522-202-XIB.pdf. [31 M a y 2006]. Sungro Horticulture Canada Ltd. 2004. The peat moss industry, [online] Available: http://www.sungro.com/about_industry.php. [31 M a y 2007]. 16 Tomassen, H.B.M., Smolders, A.J.P., Lamers, L.P.M. and Roelofs, J.G.M. 2004. Development of floating rafts after the rewetting of cut-over bogs: The importance of peat quality. Biogeochemistry. Kluwer Academic Publishers. The Netherlands. 71:69-87. Van Schie, W.L. 1999. The use of peat moss in horticulture. Proc. Int. Peat Moss Conference, Peat Moss in Horticulture, Development of the Role of the Peat Moss in Horticulture, Amsterdam, The Netherlands. Van Liere kleurrijke communicate, Emmen, The Netherlands. Verdonck, O and Gabriel, R. 1988. Substrate requirements for plants. Acta Horticulturae. Proc. Symposium on Horticultural Substrates and Their Analysis. G l . Avernaes, Funen, Denmark, ISHS, The Netherlands. Visscher, H.R. 1975. Structure of mushroom casing soil and its influence on yield and microflora. J. of Agric . Sci. 23: 36-47. Waksman, S.A. and Stevens, K.R. 1928. Contribution to the chemical composition of peat. II. Chemical composition of various peat profiles. Soil Sci. 26: 239-251. Waksman, S.A. and Stevens, K.R. 1929. Contribution to the chemical composition o f peat. II. Chemical composition of various peat profiles. Soil Sci. 26: 113-137. Wever, G. 1995. Physical analysis of peat and peat-based growing media. Proc. Int. Sym. on Growing Media and Plant Nutrition in Horticulture. Naaldwijk, The Netherlands. ISHS. Leuven, Belgium. 17 Wever, G . and Hertogh Pon, M . 1993. Effects of self-heating on biological, chemical and physical characteristics of peat. Proc. Int. Sym. on Horticultural Substrates Other Than Soi l In Situ, Florence, Italy. ISHS, Wageningen, The Netherlands. White, J .W. 1965. The concept of the container capacity and its application to soil moisture fertility regimes in the production of container grown crops. Ph.D. thesis. Perm. State University, University Park, Perm, U S A . 18 2. Q U A L I T Y O F M E D I U M G R A D E P E A T M O S S A S A C O M P O N E N T O F G R O W I N G M E D I A 1 2.1. Introduction Canada has about 111 mil l ion ha of peat bogs that make up 25% of the world's peat (Hood, 1999). Peat moss is harvested from less than 0.014% of the total land covered by peat bogs in Canada (Daigle and Daigle, 2001; Bergeron, 1996). Growing media used in ornamental horticulture industry (greenhouse and nursery) may include various bulk ingredients (peat, bark, coconut husk, perlite, pumice); however, peat moss is the most commonly used component (Hood, 1999). Quality of a growing medium is crucial to plant health, since plants in containers have only a small volume of growing media from which to satisfy air, water, and nutrition needs. Good quality growing media aid in avoiding plant stress and thereby minimize susceptibility to opportunistic diseases and insects. Avoid ing plant stress reduces fungicide and pesticide use and increases operation efficiency and product quality. Peat moss is the most commonly used ingredient of growing media due to its low bulk density (0.06 to 0.1 M g m"3), high porosity (74% by vol.), high C E C (110 and 130 cmol c kg" 1), low salinity (usually E C < 0.1 dS m"1), and pH between 3 and 6 (Bunt et al., 1988; Ranneklev, 2003). In addition, peat moss is generally free of pathogens and weed seeds (Van Schie, 1999; Reedy, 2005). Various studies have shown that the quality of peat moss is affected by type of bog vegetation, depth of harvested bog layers, and 1 A version of this chapter will be submitted for publication in Canadian Journal of Soil Science. 19 methods of harvesting and processing (Noble et al., 1999; Tomassen et al., 2004). Peat moss of the greatest quality is generally harvested from Sphagnum bogs and from upper, and less decomposed bog layers (Visscher, 1988). The European peat industry is concerned that length of the peat moss storage time may have negative impacts on peat's quality. Growing media producers in B C use peat moss that has been stored in bales for eight to 10 months. Peat quality standards are well established in Europe (Wever, 1991; Wever and van Leeuwen, 1995; Wever, 1995), but there are no formal standards in Canada. Shortcomings in growing media quality often go unnoticed until significant crop reduction occurs. A t that point it can be very difficult, costly, and even impossible to get the crop back on track. Increased Canada - U .S . border security, the introduction of new pests and diseases, and growing popularity of quality programs such as International Organization for Standardization (Wever, 1995; de Kreij , 2005) have resulted in greater customer demand for quality control of growing media. There is limited research in Canada on quality of peat moss as a component of growing media and this study sheds some light on issues related to quality of this important component commonly used in ornamental horticulture industry. The objective of this study was to evaluate the effects of peat moss source and length of storage time on the quality of peat moss. Hypothesis tested were: (i) peat moss harvested from the Manitoba Sphagnum bog (in the early stage of exploitation) had higher quality than peat moss harvested from the sphagnum bog in Alberta (in the later 20 stage of exploitation), and (ii) peat moss stored for one month in bales was of a higher quality than peat moss stored in bales for three or 10 months. 2.2. Mater ia ls and Methods 2.2.1. Site description Peat moss used in this study was harvested from a Sphagnum bog near Lake Winnipeg in Manitoba (52° 0 7 ' N and 97° 15 ' W) and a Sphagnum bog near Vi lna , Alberta about 150 km northeast of Edmonton (54° 06' N and 111° 55' W). Upper layers of bogs in Alberta and Manitoba are usually frozen from November to early May ; hence, peat harvest is generally carried out from late M a y through October. Harvesting of the peat moss from the bog in Manitoba commenced in 2004. The peat moss samples used in this study were from the second harvest done in M a y 2005. Harvesting of the bog in Alberta started about seven years prior to this study (i.e., around 2000). Peat moss supplied by the harvesting company in Manitoba is less crushed or damaged (due to careful processing) than the peat supplied by the harvesting company in Alberta (Principe, personal communication, 2005). Prior to the harvest, trenches were installed (Photo 1) in both bogs to drain near-surface water, all vegetation was removed, and the surface was harrowed to 7-10 cm depth to expose the top layer of peat moss to the sun and wind. Upon drying, the peat moss was harvested (i.e., vacuumed) with heavy harvesting machinery (Photo 2), screened into different grades (Photo 3), and compressed into bales (Photo 4). In my study, only the medium grade peat moss was analyzed. This grade is usually used for bedding and potting plants in large containers (diam. > 10 cm). Medium grade peat has 96-98% of the particles < 9.5 mm,' 89-93% of the particles < 6.5 mm, 81-88% of 21 the particles < 4.75 mm, 73-76% of the particles < 2.36 mm, 57-61%o of the particles < 1.18 mm, and 35-40%) of the particles < 0.6 mm (Note: the percentages of the particles is the percent passing each sieve). The bales were sent directly to the growing media companies such as "West Creek Farms" in Fort Langley, B C (the industrial collaborator for this study). Volumes of peat moss bales from Alberta and Manitoba were 1.48 m 3 and 1.72 m 3 , respectively. 22 Photo 1. Trenches were installed as part of Photo 2. Vacuum harvesting machine the bog preparation for harvesting Photo 3 . Processing of the peat moss Photo 4. Baling of the peat moss 2.2.2. Sampling The peat moss bales arrived at "West Creek Farms" in Fort Langley, B C in May-June 2005 and were stored outdoor for the duration of this study. Nine bales of peat moss harvested in the bog in Manitoba and nine bales of peat moss harvested in the bog in Alberta were sampled. First sampling was done on June 9, 2005 (for Manitoba peat) and 23 July 8, 2005 (for Alberta peat, since this shipment arrived a month later than the previous). The second sampling (corresponding to the three months storage time) was done on the same bales, on September 22 and 24, 2005, while the third sampling (corresponding to the 10 months storage time) was done on A p r i l 5 and 7, 2006. At each sampling time, a new side of the bale was sampled, which allowed a consistent depth of sampling. A n U-shaped cut (about 15-20 cm wide) was made on the side of the bale and the first 15 cm of the peat moss was discarded. The peat moss odor was checked and about 10 L of peat moss was taken and kept in closed plastic containers. The bales were sealed with duct tape and protected from the rain with caps. Each 10-L sample was thoroughly mixed by running it through a splitter three times. Clumps that could not go through the splitter were broken by hand and peat moss chips (pieces that stuck together and that could not be easily broken by hand) were put back into the sample. 2.2.3. Labora tory Analysis Total elements were determined on a 7.9 M HNO3, and 2.42 M HC1 extract (Smoley, 1992). Ash content was determined by weight loss on ignition at 375-600°C (Karam, 1993). Ash color was rated according to the Munsell Soi l Color notation on ashes. Size distribution of organic particles was determined by both dry (Sheldrick and Wang, 1993) and wet (Dinel and Levesque, 1977) sieving methods. During dry sieving, samples (of about 2 L) were oven dried at 50°C for 8-12 hours and sieved through a set of six sieves. Dry sieving was performed for 10 minutes in a motor-driven mechanical device with a rate of 140 beats per minute. The sieve sizes used in this study (9.50, 6.30, 24 4.75, 2.36, 1.18, and 0.60 mm) were recommended by staff at "West Creek Farms" company, since these sieve sizes correspond with the particle sizes of concern for the growing media industry than sieve sizes recommended by the American Society for Testing and Materials ( A S T M ) (iie., 4.67, 2.00, 0.420, and 0.074 mm) (Sheldrick and Wang, 1993). The sample fractions left on each sieve after sieving were weighed and the percentage of the sample passing each sieve was calculated. For the wet sieving (Dinel and Levesque, 1977), I constructed a modified apparatus (Dinel and Levesque, 1977) that consisted of a plastic bucket (inner diam. of 30 cm and a height of 36 cm) attached to a laboratory compressed air tap with a rubber tubing (about 1.5 cm in diam. and 70 cm long). A set of four sieves (each 21 cm in diam.), with openings of 1, 0.425, 0.150, and 0.075 mm, was used. The sieves were sealed individually with plastic rubber bands around the bottom edge of each sieve (Photo 5), stacked on the top of each other, and secured by placing clamps at the top and bottom of the stack (Photo 6). The stack of four sieves was placed into the bucket and the top of the bucket was closed loosely with the l id, which had an entry for the air tube (Photo 7). 25 Photo 7. The bucket connected to the air tap Twenty five grams of moist peat moss was placed into a 500 m L plastic flask and 300 m L of distilled water was added. The flasks were placed into a reciprocating shaker for 16 hours. After shaking, the suspension was poured onto a 0.075 mm sieve and washed with water to remove the material finer than 0.075 mm. The stack of four sives was inserted into the bucket and the material left on the 0.075 mm sieve was transferred to the top sieve of the sieve stacks (i.e., 1 mm) and the bucket was filled with water so that it covered the sample on the top sieve. A i r was introduced to the system to bubble 26 vigorously for 2 hours and shake the sieves. The water content of the peat moss samples used for wet sieving was determined gravimetrically on separate sub-samples. In the original method by Dinel and Levesque (1977), shaking was done for 1 hour. The material left on each sieve was filtered through a filter paper (filter paper number was not specified), dried at 70°C for 24 hours, and weighed. The proportion of the sample in each particle size range is expressed as a percentage of dry weight (Parent and Caron, 1993). M y modification of the wet sieving method consisted of weighing the empty sieves individually followed by weighing each sieve with the peat moss fraction on it. Then a sub-sample of the peat remaining oh top of each sieve (after wet sieving) was taken, oven dried at 70°C for 24 hours and water content of this sub-sample was used to calculate the percent of the particles passing from each fraction. This allowed me to skip the time-consuming washing of each sieve and subsequent filtering. Gravimetric water content was determined by oven-drying about 2 L of peat moss samples at 70°C for 8-12 hours (Topp, 1993). The gravimetric water content was calculated based on the wet weight. Since calculating the water content based on dry weight produce numbers greater than 100%, "West Creek Farms" company calculates the gravimetric water content based on the wet weight, which makes it more understandable for growers (Principe, personal communication, 2005). Water retention was determined on a 0.5 M P a pressure plate extractor (Klute, 1986) and water content was reported at 0.002, and 0.05 M P a . The difference between 0.002 M P a and 0.05 M P a was used as the plant available water. 27 The soil p H and E C were determined by the saturated media extract method ( B C M A F F , 1999). The advantage of this method over other dilution methods (e.g., 1:1.5, 1:2, 1:5 soil to water ratio) is that the volume of the sample and initial water content of the sample do not affect the accuracy of measurements. If a dilution method is used in growing media testing, the compression of the growing media samples (e.g., peat moss) before saturation should be similar in all containers, so the tests could be reproducible and results could be comparable. In the B C M A F F protocol after saturating the sample, p H is determined directly from the saturated peat moss and E C is determined after vacuuming or squeezing the extract out of the sample. This method has been modified at "West Creek Farms" company. In order to extract the solution from the sample for p H and E C determination, the saturated sample was prepared in a container with an opening at the bottom. The opening was closed by a rubber plug, and the container was placed on top of an empty container (Photos 8 and 9). Peat sample was placed into the container (the volume of peat moss used, depends on the volume of the container). To reduce the high hydrophobicity of peat moss, the samples were sprayed with 1% surfactant solution (Smithers-Oasis professional M W A concentrate liquid wetting agent) prior to saturation. Saturated paste was made with adding water to the sample. Then saturated paste was left for 45 minutes (Photo 10), plug was removed, and the container was put back on top of the empty container for 30 minutes to collect the solution. 0 28 Photo 8. Top container with a plug in the bottom hole and a second container for solution collection Photo 10. Saturated paste of a peat moss sample 29 Available N H 4 and NO3 were determined on a 2 M KC1 extract (Keeney and Nelson, 1982). Odor of the peat moss was determined qualitatively using the scale developed at "West Creek Farms" company. The scale included the following categories: odorless, earthy, lakey, musty, "wet dog", and manure. Immediately upon making the U-shaped cut on the bale, outer 15 cm of peat moss was removed, and the odor category was determined by sniffing. A weed germination test was performed in a greenhouse. Samples of about 5 L were placed in a 60 x 25 cm weed trays and 40 g (or 9 g/L) of dolomite was added to the peat moss to encourage germination (Bos et al., 2003). The 0.01% surfactant solution was sprayed on top of the peat moss to reduce hydrophobicity of the peat moss and facilitate the irrigation process. The trays were watered daily. The numbers of the emerged weeds .were recorded once per week. After six weeks, weeds were transplanted into 4-inch (10.16cm) pots. A couple grains of super phosphate were added to the pots to enhance weed growth so that weeds could be identified after flowering. Trays with more than three weeds were considered unsatisfactory according to the European peat moss quality standards (Bos et al., 2003). 2.2.4. Statistical Analysis Soil quality indicators were analyzed as a split-plot, completely randomized design with nine replications. Peat moss source (i.e., bog type) was the main plot treatment; storage time was the sub-plot treatment, while nine bales were replications. The S A S general linear model procedure was used (SAS Institute, 1990). Following a significant 30 F-test, differences between means were evaluated using Bonferroni multiple comparison test. Results were considered significant atp<0.05. 2.3. Results and Discussion 2.3.1. Site Conditions Total elements, ash content, and ash color are shown in Table 2.1. Peat moss harvested from two bogs differed in terms of ash color and most of the elements. Total P and K , most of micronutrients (Fe, M n , Cu , Zn, and B) , and a majority of the other elements ( A l , As , Na, N i , Pb, and Si) were greater in the Manitoba peat moss than the Alberta peat moss. 31 Table 2.1. Total elements (mg kg"1), average ash content (mg 100 g"1) and ash color of peat moss stored for one month, harvested from a bog in Manitoba and a bog in Alberta (standard error of the mean in the brackets, n=9). Property Manitoba peat Alberta peat t-value moss moss Macronutrients mg kg"1 P 6.2 (0.54) 2.7 (0.28) 6.90* K 9.4 (0.75) 1.3 (0.3) 10.96* Ca 53.3 (3.52) 186.4(11.78) -9.75 Mg 17.1 (1.62) 20.5 (1.14) -0.86 Micronutrients Fe 22.0(1.75) 10.0(1.03) 7.97* Mn 2.5 (0.23) 2.0(0.17) 2.45* Cu 0.0 (0.00) 0.0 (0.00) 5.68* Zn 0.3 (0.04) 0.1 (0.07) 5.85* B 0.0(0.01) 0.0 (0.03) 0.11 Mo 0.0 (0.00) 0.0 (0.00) -Other elements Al 21.9 (2.03) 6.9 (0.67) 8.15* As 0.0 (0.00) 0.0 (0.00) 4.52* Ba 0.3 (0.03) 0.3 (0.01) 1.63 Cd 0.0 (0.00) 0.0 (0.00) -Co 0.0 (0.00) 0.0 (0.00) -Cr 0.0 (0.00) 0.0 (0.00) -Na 1.9(0.28) 0.7 (0.08) 4.98* Ni 0.1 (0.05) 0.0(0.01) 2.91* Pb •0.2 (0.02) 0.0 (0.00) 12.06* Se 0.0 (0.00) 0.0 (0.00) -0.47 Si 4.1 (1.13) 1.7(0.64) 3.95* Sr 0.1 (0.02) 0.8 (0.01) -10.75 mg 100 g" i Ash content 4.36 (0.003) 6.48 (0.002) -5.23 Ash color 10YR8/4 10YR8/2 *significantly different at p < 0.05 Ash of the Manitoba peat was more intense in color (10YR8/4), while the ash of the Alberta peat was of a somewhat lighter color (10YR8/2). The more intense color of 32 Manitoba peat is the result of higher Fe content in the Manitoba peat (Table 2.1). The ash content was similar between the two peat sources. 2.3.2. Size Distr ibut ion of Organic Particles Determined by the D r y Sieving Method Size distribution of organic particles in a peat moss is commonly monitored during creation of growing media. At one month storage time, five out of six size fractions of the Manitoba peat moss had significantly lower percentage of particles that passed the corresponding sieve relative to the Alberta peat moss (Figure 2.1a). A t three months of storage time, Manitoba peat moss still had a significantly lower percentage of particles passing most sieve sizes, with exception of 1.18 and 4.75 mm (Figure 2.1 b). Finally, at 10 months of storage time, Manitoba peat moss still had lower percentage of particles passing all sieve sizes, with exception of 4.75 mm size fraction (Figure 2.1 c). The overall dominance of the larger particles in the Manitoba peat (Figure 2.1) coincides with the early harvesting stages of this bog. Peat moss harvested during early stages of bog excavation is usually less decomposed and as such is more valuable for the growing media industry. Harvesting of peat moss in the Manitoba bog started recently (i.e., in spring of 2004), while the bog in Alberta has been excavated for about seven years. Numerous studies (Puustjarvi, 1976; Verdonk and Gabriel, 1988; Riviere, 1992) showed that the quality of peat moss decreased with decline in particle size and associated decline in water retention and air filled porosity (represents the difference between the total porosity and volumetric water content at container capacity). The attenuation of stored air is attributed to the increase of particles smaller than 1 mm or 0.5 mm (Puustjarvi, 1976; Verdonk and Gabriel, 1988; Riviere, 1992). Decrease of the 33 particle size from early to late stages of bog excavation may result from enhanced microbial decomposition (Caron and Riviere, 2003). 100 80 60 20 Manitoba Alberta fa fa J El 1 1 0.60 1.18 2.36 Fraction size 4.75 (mm) 6.35 9.50 8 to (b) 3 months * 0 0 0.60 1.18 2.36 4.75 Fraction size (mm) 6.35 9.50 100 80 g 4 0 (c) 10 months 0 XA XA XA * 0.60 1.18 2.36 4.75 6.35 9.50 Fraction size (mm) Figure 2.1. Percent of organic particles (determined by dry sieving method) of Manitoba and Alberta medium grade peat moss passing each sieve size at (a) one, (b) three, and (c) 10 months storage time. Error bars represent standard error of the mean (n=9). Means for bog types following * are significantly different atp< 0.05. w Percent of particles passing each sieve of the Manitoba peat moss was similar at all three times of storage (Figure 2.2 a). The only exception was 1.18 mm size fraction , where percentage of particles passing that particular sieve was greater at three months relative to the one month of storage time. Similarly, there were no significant differences 34 among the three storage times in any of the fraction sizes of Alberta peat moss (Figure 2.2 b). This implies that storage time did not affect peat moss quality and that the self-heating process was not intense enough to induce decomposition. In a study on effect of self-heating on stockpiles of Sphagnum peat moss, Puustjarvi (1983) indicated that self-heating may lead to decrease in particle size and water retention (author did not specify the length of storage time). 35 100 80 ro Q. c 8 40 CL 20 a) Manitoba 0.60 1.18 2.36 4.75 6.35 9.50 Fraction s ize (mm) 100 1.18 2.36 4.76 6.35 Fraction size (mm) F i g u r e 2.2. Percent of organic particles (determined by dry sieving method) of Manitoba medium grade peat moss (a) and Alberta medium grade peat moss (b) passing each sieve at one, three, and 10 months of storage time. Error bars represent standard error of the mean (n=9). Means for storage time labeled with the same letter are not significantly different (p<0.05) 36 2.3.3. Size Distr ibut ion of Organic Particles Determined by the Wet Sieving Method When particle size distribution was determined by wet sieving, the Manitoba peat moss had a significantly lower percent of particles passing through each corresponding sieve than the Alberta peat moss (Figure 2.3). This was true for all fraction sizes and times of storage. Since harvest the bog in Alberta has been going on for longer time (about seven years) than in the bog in Manitoba (excavation started in 2004), it was not surprising to find finer particles in the Alberta peat where peat was excavated from deeper, more decomposed layers. These data obtained by the wet sieving method are in agreement with particle size distribution data determined by the dry sieving method (Figure 2.1). 37 100 80 £60 840 20 Manitoba Alberta a) 1 month 0.15 0.425 1 Fraction size (mm) 0.15 0.425 1 Fraction size (mm) 100 0.15 0.425 1 Fraction size (mm) Figure 2.3. Percent of organic particles (determined by wet sieving method) of Manitoba and Alberta medium grade peat moss passing each sieve size at (a) one, (b) three, and (c) 10 months storage time. Error bars represent standard error of the mean (n=9). Means for bog types following * are significantly different atp < 0.05. In all size fractions of the Manitoba peat moss, the percent of particles passing the corresponding sieve sizes was significantly higher for peat moss stored for 10 months than for one and three months (Figure 2.4 a). The same result was obtained for the Alberta peat moss, with the exception of the 0.15 and 1 mm size fractions (Figure 2.4 b). In the 0.15 mm size fraction, the 10 months stored peat moss had a higher percent of particles passing the corresponding sieve size relative to the peat stored for three months 38 (Figure 2.4 b). In 1 mm size fraction, peat moss stored for 10 months had a higher percent of particles passing the sieve than the peat stored for one month (Figure 2.4 b). Figure 2.4. Percent of organic particles (determined by wet sieving method) of medium grade peat moss harvested from the Manitoba bog (a) and Alberta bog (b) passing each sieve at one, three, and 10 months of storage time. Error bars represent standard error of the mean (n=9). Means for storage time labeled with the same letter are not significantly different (p<0.05). Storage time affected the size of the particles in both peat mosses, resulting in the dominance of finer particles at longer storage tome (i.e., 10 months). Similarly, Puustjarvi (1983) reported that due to the self-heating and the decomposition of stockpiled peat the proportion of particles smaller than 1 mm was greater than 50%, while the expected proportion of fresh peat particles with diameter <1 mm ranged from 20 to 40% (author did not specify the length of storage time). In my study, both dry and wet sieving methods were used to determine size distribution of organic particles. The dry sieving method (Sheldrick and Wang, 1993), which is commonly used by the growing media industry, is quick, inexpensive, and relatively easy to carry out. It; however, is associated with relatively large losses of the 39 sample as dust during sieving and the likely crushing of the oven dried particles during shaking. The wet sieving method (Parent and Caron, 1993) is more time consuming since it takes about 1 to 2 hours to complete sieving of one sample. The advantages of the wet sieving method include lower sample losses during sieving relative to the dry sieving method and lower breakage of organic fibers during shaking. It is not surprising that in my study, differences among the study treatments (storage time) were observed when data were obtained by wet sieving, but treatment effects on particle size distribution were not observed in dry sieving. Even though wet sieving is more time consuming than dry sieving, the growing media industry should consider switching to wet sieving in order to obtain more reliable and reproducible data. Since sizes of the sieves used in dry and wet sieving during this study were not the same, direct comparison of these two methods was not possible. A study involving the same sieve sizes used by both methods should be carried out to directly compare these two methods. 2.3.4. Gravimetr ic Water Content The gravimetric water content (based on wet weight) of the Manitoba peat moss was significantly greater relative to the Alberta peat moss (Table 2.2). This was most likely due to the better structure (arrangement) of the Manitoba peat moss particles, which has been excavated from the upper layers of the bog. Storage times had a significant effect on gravimetric water content. Peat moss was the driest at one month storage time, while the greatest water content was obtained at three months storage time (Table 2.2). 40 Table 2.2. Gravimetric water content (on wet mass bases) of Manitoba and Alberta medium grade peat moss stored for one, three, and 10 months (standard error of the mean in the brackets, n=9). Means for storage time labeled with the same letter are not significantly different (p<0.05). Bog type Storage time (months) Water content (g/g) 1 0.55 (0.019) Manitoba 3 0.60(0.021) J O 0.59 (0.023) 1 0.52(0.016) Alberta 3 0.54(0.011) 10 0.54(0.010) c r • .. • JS • ' F-value Source of variation aj Bog type (B) 1 81.52* Storage time (S) 2 15.56* B x S 2 .2.22 F-values following * are significantly different atp<0.05. 2.3.5. Plant Avai lable Water The plant available water was calculated as the difference between water contents determined at 0.002 and 0.05 M P a . Bog type as well as the length of the storage time did not have a significant effect on the plant available water (Table 2.3). This is in disagreement with the particle size distribution data obtained by the wet sieving method, which showed that the Manitoba peat moss was dominated by the presence of larger particles relative to the Alberta peat moss (Figure 2.4). It is generally understood that peat moss with smaller particle size could have a greater water holding capacity (Puustjarvi, 1983), but this was not confirmed in my study. 41 Furthermore, organic particle size data obtained by the wet sieving method showed that the organic particles were smaller after 10 months than one month of storage time (Figure 2.4). This was true for both Manitoba and Alberta peat moss. It is possible that self-heating in peat and subsequent decomposition that occurred during the storage led to formation of water-repellant compounds such as dried humic acids (Puustjarvi, 1983). Since in my study no difference in plant available water was observed between two storage times, even though the particle size was decreased 10 months of storage, it is likely that the degree of the particle size reduction and decomposition were not high enough to result in a decline in plant available water after 10 months of storage time. Water repellent substances possibly generated during decomposition, are the products of lignin decomposition. Puustjarvi (1983) suggested that lack of woody residues in peat moss could lead to the absence of water repellent humic substances. A s a result, storage time would not alter plant available water in peat moss. In samples used in my study also lack of woody debris could be a reason for lack of change in plant available water in spite of decrease in particle size. 42 Table 2.3. Plant available water of Manitoba and Alberta medium grade peat moss stored for one and 10 months (standard error of the mean in the brackets, n=9). Bog type Storage time Plant available water (cm3cm~3) (months) 1 0.13 (0.029) Manitoba 10 0.14(0.023) 1 0.14(0.029) Alberta 10 0.17(0.024) Source of variation df F-value B o g type (B) 1 2.90 Storage time (S) 1 0.78 B x S 1 0.12 F-values following * are significantly different at /?<0.05 2.3.6. Chemica l Properties At all three times of storage, Manitoba peat moss had a significantly lower p H relative to the Alberta peat moss (Table 2.4). Since total A l and Fe contents of the Manitoba peat moss were greater than in the Alberta peat moss (Table 2.1), it is not surprising that acidity was greater in Manitoba peat moss (Table 2.4). Obtaining lower p H in Alberta peat moss than Manitoba peat moss in my study contradicted the findings of the study done by Nobel et al. (1998) who reported lower p H of 3.5 in the black Sphagnum peat moss (deeper, more decomposed layers of a bog), relative to higher p H of the brown Sphagnum peat moss (upper, less decomposed layers o f a bog). Will iams and Wheatley (1988) reported that the p H in blanket peat bogs increased with depth. Since 43 p H values were greater in the Alberta peat moss (which has been harvested for about seven years and from deeper layers) relative to the Manitoba peat moss, my study confirms the same result of aforementioned study. The Manitoba peat moss had a significantly lower E C relative to the Alberta peat moss (Table 2.4). The reason could be attributed to the origin of different plant species present in bogs in Alberta versus Manitoba (it is known that the these bogs are Sphagnum moss dominated, while the other possible plant species in these two bogs were unknown), or the proximity of excavation depth in Alberta to the probable alkaline parent material. Storage time had affected E C in a way that the lowest E C was obtained at one month storage time, while three month storage time had the greatest E C . Wever and Hertogh-Pon (1993) indicated that the raise in the temperature from 50°C to 67°C caused a higher E C in self-heating induced peat moss. Same result was obtained from my study (the temperature was not measured in my study). The Manitoba peat moss had greater level of N H 4 - N than the Alberta peat moss (Table 2.4). Storage time also significantly affected the N H 4 - N content. One month storage time had the greatest N H 4 - N content, while 10 month storage time had the lowest N H 4 - N content (Table 2.4). Will iams and Wheatley (1988) reported that the amount of N H 4 - N decreased with depth in oligotrophic peat (very low nutrient peat blankets where plant growth is inhibited). M y data are in agreement with the findings about N H 4 - N level, since lower N H 4 - N was observed in the Alberta peat moss, which was excavated from lower depths. The reason might be attributed to the decrease of aeration with depth and lower amount of other nutrients such as P and K (Table 2.1) in the Alberta peat in comparison to the Manitoba peat. The lower amount of oxygen inhibited bacterial 44 activity and the low amount of P and K limited the microbial activity and consequently the amount of mineralized N . T a b l e 2.4. Reaction (pH), electrical conductivity (EC), and N H 4 - N content of Manitoba and Alberta medium grade peat moss stored for one, three, and 10 months (standard error of the mean in the brackets, n=9). Means for storage time labeled with the same letter are not significantly different (p<0.05). Bog type Storage time E C N H 4 - N ' p H in water (months) (dS m"1) (mg kg"1) 1 4.2 (0.07) 0.06 (0.00) 200(10.0) Manitoba 3 4.4 (0.07) 0.07 (0.01) 190 (20.0) 10 4.3 (0.03) 0.06 (0.01) 150(20.0) 1 4.7 (0.05) 0.25 (0.02) 40(10.0) Alberta 3 4.6 (0.05) . 0.29(0.02) 30(10.0) 10 4.8 (0.03) 0.27 (0.02) 30(10.0) Source of variation df F-value Bog type (B) 1 120.92* 778.39* 70.45* Storage time (S) 2 1.75 4.95* 3.77* B x S 2 4.36* 2.08 2.88 F-values following * are significantly different at p<0.05. In general, the level of N O 3 - N was very low in both peat types. Manitoba peat moss had a lower level of N O 3 - N content than Alberta peat moss. Storage time did not 45 affect the N O 3 - N in Manitoba peat moss (Table 2.5). The N O 3 - N in Alberta peat moss stored at one month was significantly lower than in peat moss stored for three months (Table 2.6). Since the variance was very high in the data set, which results in rejection of normality assumption, one-way analysis of variance was done on this data and the two peat mosses had been analyzed separately in order to obtain the significance of the storage time on each bog separately. Will iams and Wheatley (1988) also observed trace amounts of N O 3 - N in freshly collected samples of peat moss from an oligotrophic deep blanket bog in Scotland and that was attributed to the absence of ammonium-oxidizing bacteria. The lower level of N O 3 - N in the Manitoba peat moss could be attributed to the low level of p H (Table 2.2) in the Manitoba peat moss that inhibits the activity of the nitrifying bacteria. 46 T a b l e 2.5. Nitrate-N content of Manitoba medium grade peat moss stored for one, three, and 10 months storage time (standard error of the mean in the brackets, n=9). F-values following * are significantly different at p<0.05. B o g type Storage time N O 3 - N (mg kg") (months) 1 0 Manitoba 3 10(0.0) 10 10(0.0) Source of variation df F-value Storage time 2 0.40 T a b l e 2.6. Nitrate-N content of Alberta medium grade peat moss stored for one, three, and 10 months (standard error of the mean in the brackets, n=9). F-values following * are significantly different at /?<0.05. Means for storage time labeled with the same letter are not significantly different (p<0.05). Bog type Storage time N 0 3 - N ( m g kg"1) (months) 1 30 (10.0) a Alberta 3 50 (10.0) b 10 40 (10.0) a Source of variation df F-value Storage time 2 10.99* 47 2.3.7. Odor Twenty two percent of the Manitoba peat moss samples had earthy odor, 11% had the "wet dog" odor, while 66% of samples were odorless (Table A . 12). The Alberta medium grade samples were all odorless (Table A . 13). The results from odor tests indicate that the odor of peat moss in Manitoba would be a concern for consumers. The odor of Manitoba peat moss samples turned to earthy after three and 10 months storage time, and the longer storage time aided in disappearance o f the odor in Manitoba peat moss. In general, i f smelly bales are identified a couple of days of aeration is usually enough to eliminate the odor. 2.3.8. Content of Weeds Eighty nine percent of the Manitoba peat samples showed no weed germination, while 11% of the samples had just one weed species that germinated (i.e., Taraxacum officinale Web). There was no weed germination in Alberta peat moss (Table A . 14). The critical number of germinated seeds in each tray is three (Bos et al., 2003). With less than three seeds germinated per tray, the peat moss used in my study met the requirement of good quality in terms of weed seeds presence. 2.4. Conclusions The size of organic particles (determined by both dry and wet sieving methods), gravimetric water content, and N H 4 - N content were greater in the Manitoba peat than the Alberta peat. Electrical conductivity, pH, and NO3 -N were lower in the Manitoba peat moss than the Alberta peat moss. The Manitoba peat was excavated from upper, less decomposed layers than peat moss obtained from the Alberta peat bog that is characterized by excavation of deeper, more decomposed layers. Plant available water 48 and weed seed content were similar in peat moss excavated from these two bogs. In both peat moss, organic particle size (determined by wet sieving method) was decreased at 10 months, EC was increased at three months, and NH4-N content was decreased at 10 months storage time. Also NO3-N content was increased at three months storage time only in Alberta peat moss. Other peat moss properties were not affected by the length of storage time. My data on the particle size distribution indicated that the growing media industry should consider using storage time shorter than 10 months. Prolonged storage time (10 months) decreased the size of the organic particles, which is not desirable for industry. Since the amount of available N is susceptible to change during the storage time, another recommendation for the growing media industry based on the findings of my study is to monitor available N content at the time when peat is incorporated into various mixes. The possible side effects of the peat moss with high content of N on low In-tolerant plants can be avoided by monitoring N-content in peat moss. The wet sieving method is a more accurate test of particle size distribution, since it demonstrated the difference between the treatments. The growing media industry is using the dry sieving method since it is fast and easy to perform. Nonetheless, the risks of obtaining none-reproducible results associated with this method are too high to ignore. These risks include (i) breaking of delicate oven-dried particles during sieving, and (ii) high losses of the dust fraction during sieving. Thus, I would recommend that the growing media industry uses the wet instead of the dry sieving method. 49 2.5. References Bos, E .J. , Keijzer, R.A., Van Schie, W.L., Verhagen, J.B. and Zevenhoven, M.A. 2003. Growing media and substrates. R H P Foundation Brochure. Naaldwijk, The Netherlands. BCMAFF. 1999. On-site testing o f growing media and irrigation water. [Online]. Available at http://www.agf.gov.bc.ca/ornamentals/floriculture/testing.pdf. [31 M a y 2007]. Bergeron, M. 1996. Peat. [Online]. Available: http://www.nrcan.gc.ca/mms/cmy/content/1995/44.pdff31 M a y 2007]. Bunt, A.C, Hons, N.D.H. and Biol, M.I. 1988. Material for loamless mixes. Pages 6-39 in Media and mixes for container-grown plants. Unwin-Hyman Ltd. , London, U K . Caron, J. and Riviere, L.M. 2003. Quality of peat substrates for plants grown in containers. Pages 67-91 in L . E . Parent and P. Ilnicki, eds. Organic soils peat materials sustainable agriculture. C R C Press, Florida, U S A . Canadian Sphagnum Peat Moss Association. 2005. Growing Media and Soi l Amendment (A Horticulture Curriculum). St. Albert. Alberta. De Boodt, M. and Verdonck, O. 1972. The. physical properties of the substrate in horticulture. Pages 37-44 in Proc. I l l Sym. on Peat in Horticulture. V o l 26. Dublin, Ireland. 50 de Kreij, C. and Wever, G. 2005. Proficiency testing of growing media, soil improvers, soils, and nutrient solutions. Commun. Soil Sci. Plant Anal . 36: 81-88. Daigle, J. and Gautreau-Daigle, H. 2001. Canadain peat harvesting and the environment. North American Wetland Conservation Council Committee. Ottawa. Dinel, H. and Levesque, M. 1976. Une technique simple pour l'analyse granulometrique de la tourbe en milieu aqueux. Can. J. Soil Sci . 56: 119-120. Hood, G. 1999. Canadian peat harvesting and its effect on the environment. Proc. Int. Sym. Growing media and Hydroponics. . Windsor, Ontario. ISHS. The Netherlands. Karam, A . 1981. Chemical properties of organic soils. Pages 459-471 in M . R . Carter, ed. Soil Sampling and Methods of Analysis. Canadian Soi l Science Society, Lewis Publishers, Florida. Keeney, D.R. and Nelson, D.W. 1982. Inorganic nitrogen. Pages 643-698 in R . H . Mil ler , and D.R. Keeney, eds. Methods of soil analysis. Part 2. 2 n d ed., Agron. Monogr. 9. A S A - S S S A , Madison, W L Klute, A . 1986. Water retention. Pages 635 - 662 in A . Klute, ed. Methods of soil analysis. Part 1. 2 n d ed., Agron. Monogr. 9. A S A - S S S A , Madison, W L Noble, R., Dobrovin Pennington, A . , Evered, C E , and Mead, A . 1998. Properties of peat-based casing soils and their influence on the water relations and growth of the mushroom (Agaricus bisporus). Plant and Soi l 207: 1-13. Paivanen, J. 1973. Hydraulic conductivity and water retention in peat soils. Acta Forestalia. Fennica, Helsinki, Finland. 70 pp. Parent, L.E. and Caron, J. 1993. Physical properties of organic soils. Pages 441-471 in 51 M . R . Carter, ed. Soil Sampling and Methods of Analysis. Canadian Soi l Science Society, Lewis Publishers, Florida, U S A . Puustjarvi, V. 1983. Effect of self-heating in stockpiles on the structure of horticultural peat. Pages 57-63 in Peat and Plant Yearbook. Association of Finnish peat industries, Helsinki, Finland. Ranneklev, S.B. and Baath, E. 2003. Use of phospholipid fatty acids to detect previous self-heating events in stored peat moss. App l . Environ. Microbiol . 69: 3532-3539. Reedy, S. 2005. Is peat helping you? Grower talks. March 2005. pp 32-34. Riviere, L.M. 1992. Water cycles of substrate-plant system in soilless culture (in French). Universite d'Angers, Ecole Nationale dTngenieurs des Travaux de l'Horticulture et du Paysage d'Angers, Angers, France, 141 pp. SAS Institute. 1990. S A S user's guide: Statistics. Version 6, 4th ed. S A S Inst. Cary, N C , U S A . Sheldrick, B.H. and Wang, C . 1993. Particle size distribution. Pages 499-511 in M . R . Carter, ed. Soil Sampling and methods of Analysis. Canadian Soil Science Society, Lewis Publishers, Florida, U S A . Smoley, C .K. 1992. Methods for the determination of metals in environmental samples. Environmental monitoring systems laboratory. Office of Research and Development. U . S . Environmental Protection Agency. Cincinnati, Ohio, U S A . Tomassen, H.B.M., Smolders, A.J.P., Lamers, L.P.M. and Roelofs, J.G.M. 2004. Development of floating rafts after the rewetting of cut-over bogs: The importance of peat quality. Biogeochemistry 71: 69-87. Topp, G .C. 1993. Soil water content. Pages 541-543 in M . R . Carter, ed. Soi l Sampling 52 and Methods of Analysis. Canadian Soil Science Society, Lewis Publishers, Florida, U S A . Van Schie, W.L. 1999. The use of peat moss in horticulture. Proc. Int. Peat Moss Conference, Peat Moss in Horticulture, Development of the Role of the Peat Moss in Horticulture, Amsterdam, the Netherlands. V a n Liere kleurrijke communicate, Emmen, the Netherlands. Verdonck, O and Gabriel, R . 1988 . Substrate requirements for plants. Proc. Symposium on Horticultural Substrates and Their Analysis. G l . Avernaes, Funen, Denmark, ISHS, The Netherlands. Visscher, H . R . 1988. Casing soil in Pages 73-89 in L . J . L . D . van Griensven, ed. Cultivation of Mushrooms. Darlington mushroom laboratories, Sussex. U K . Wever,G. 1991. Guide values for physical properties of peat substrates. Proc. II Sym. on Horticultural Substrates and Their Analysis, X X I I I I H C . Guernsey U K . ISHS.Wageningen, The Netherlands. Wever, G. 1995. Physical analysis of peat and peat-based growing media. Proc. Int. Sym. on Growing Media and Plant Nutrition in Horticulture. Naaldwijk, The Netherlands. ISHS. Leuven, Belgium. Wever, G. and van Leeuwen, A . 1995. Measuring mechanical properties o f growing media and the influence of cucumber cultivation on these properties. Naaldwijk, The Netherlands. ISHS. Leuven, Belgium. Williams, B .L . and Wheatley, R .E. 1988. Nitrogen mineralization and water table height in oligotrophic deep peat. B i o l . Fert. Soils 6: 141-147. 53 3. R E C O M M E N D A T I O N S F O R F U T U R E S T U D I E S A s the source of odor is still not completely clear, a study focusing on the formation of different organic acids during self-heating process should be carried out. Organic acids could be one of the reasons for presence of ammonia like odor in peat moss. Alternatively, another study focusing on sulfur formation over the time in peat moss bales could be carried out. Sulfur can be another possible odor-making agent. A study focusing on the wet sieving method would allow establishing the proficiency of wet sieving over dry sieving. Organic peat moss particles o f a known sizes should be sieved by wet sieving to determine the accuracy of this method. A t the time being, standard particles for organic soil do not exist and may be the first step in this process is the establishment of standard particles for wet sieving. Comparing the losses of sample in both wet and dry sieving methods should also be investigated. Samples could be taken from different depths of a bale and from different sides of the bales. That would allow the researcher to have a better representative sample of peat moss in a bale. Also the temperature at the bale core could be monitored to indicate the intensity of peat decomposition within a bale. Obtaining the temperature from bales makes it possible to detect the kind of activated microbes and their effects on decomposition o f peat moss. Since the existence o f self heating in baled peat moss is unknown, monitoring the temperature and identifying microbial population should be done. 54 Appendix A Table A . l . Analysis of variance for the effect of storage time on 0.6 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method. Source of variation df F-value p-value Bog type (B) 1 110.56 O.0001 Storage time (S) 2 1.99 0.1539 B x S 2 2.24 0.1228 Table A . 2 . Analysis of variance for the effect of storage time on 1.18 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method. Source of variation df F-value /7-value Bog type (B) 1 33.22 O.0001 Storage time (S) 2 2.72 ' 0.0814 B x S 2 4.60 0.0175 55 Table A . 3 . Analysis of variance for the effect of storage time on 2.36 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method. Source of variation df F-value p-value Bog type (B) Storage time (S) B x S 1 2 2 9.98 1.18 1.87 0.0034 0.3201 0.1712 Table A . 4 . Analysis of variance for the effect of storage time on 4.75 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method. Source of variation df F-value p-value Bog type (B) Storage time (S) B x S 1. 2 2 2.99 1.70 0.76 0.0935 0.1981 0.4772 Table A . 5 . Analysis of variance for the effect of storage time on 6.35 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method. Source of variation df F-value p-value B o g type (B) Storage time (S) B x S 1 2 2 8.73 0.63 1.38 0.0058 0.5416 0.2661 56 Table A.6. Analysis o f variance for the effect of storage time' on 9.5 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by dry sieving method. Source of variation df F-value p-value Bog type (B) Storage time (S) B x S 1 2 2 19.23 1.30 1.39 0.0001 0.2877 0.2630 Table A.7. Analysis of variance for the effect of storage time on 0.15 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by wet sieving method. Source of variation df F-value /7-value B o g type (B) 1 6.95 0 .0128 Storage time (S) 2 40 .60 O.0001 B x S 2 0.92 0.4075 57 Table A .8. Analysis of variance for the effect of storage time on 0.4 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by wet sieving method. Source of variation df F-value p-value Bog type (B) Storage time (S) B x S 1 2 2 14.39 61.95 0.05 0.0006 O . 0 0 0 1 0.9495 Table A.9. Analysis of variance for the effect of storage time on 1 mm size fraction of medium grade peat moss from Manitoba and Alberta determined by wet sieving method. Source of variation df F-value p-value Bog type (B) Storage time (S) B x S 1 2 2 31.87 19.68 0.62 O . 0 0 0 1 <0.0001 0.5462 58 Table A.10. Plant available water in medium grade Manitoba peat moss stored in bales for one, three, and 10 months. Plant available water of Manitoba peat moss, (cm cm") Sample # 1 month 3 months 10 months 2 0.04 0.3 0.25 6 0.26 0.02 0.18 34 0.23 0.05 0.14 36 0.11 0.03 0.11 37 0.03 0.02 0.12 38 0.07 0.03 0.12 3 0.19 0.04 0.19 35 0.17 0.06 0.11 68 0.04 0.03 0.00 Mean ,0.13 0.03 0.14 St. dev. 0.089 0.013 0.007 59 Table A. l l . Plant available water in medium grade Alberta peat moss stored in bales for one, three, and 10 months. Plant available water of Alberta peat moss (cm cm") Sample # 1 month 3 months 10 months 19 0.24 0.01 0.17 20 0.03 0.01 0.15 42 0.03 0.005 0.24 43 0.15 0.01 0.23 65 0.27 0.02 0.25 67 0.26 0.007 0.07 69 0.30 0.03 0.11 70 0.21 0.01 0.25 71 0.08 0.03 0.31 Mean 0.14 0.001 0.16 St. dev. 0.100 0.010 0.074 Tables A. 10 and A.l 1 show the data obtained for plant available water for both Manitoba and Alberta peat moss. Plant available water data obtained at the three months of storage time were much lower relative to other two storage times, and they have been removed from the study. The reason for obtaining such low data was caused by the different method that the laboratory technician used during analysis. The technician leveled the peat moss in the rings before putting samples on the pressure plate. This changed all samples of the three months storage time and affected the volume of the peat in the rings. 60 Table A.12. Odor determined at one, three, and 10 months of storage time in Manitoba peat moss Sample number 1 month 3 months 10 months •2 earthy earthy earthy 6 odorless odorless earthy 34 wet dog wet dog earthy 36 odorless odorless earthy 37 odorless odorless earthy 38 odorless odorless earthy 3 sweet earthy sweet earthy earthy 35 odorless odorless earthy 68 odorless/lakey odorless/lakey earthy 61 Table A .13. Odor determined at one, three, and 10 months of storage time in Alberta peat moss Sample number 1 month 3 months 10 months 19 odorless odorless odorless 20 odorless odorless odorless 42 odorless odorless odorless 43 odorless odorless odorless 65 odorless odorless odorless 67 odorless odorless odorless 69 odorless odorless odorless 70 odorless odorless odorless 71 odorless odorless odorless 62 Table A.14. Number of weed seeds germinated per 60><25 cm tray in Manitoba and Alberta peat moss Manitoba peat moss Manitoba peat Alberta peat moss Alberta peat sample number moss sample numbers moss 2 0 19 0 6 0 20 0 34' 0 42 0 36 0 43 0 37 0 65 0 , 38 0 67 0 3 0 69 , o 35 0 70 0 68 2 71 0 Total 2 0 63 Table A.15. Water content (cm 3 cm ~3) at 0.002, 0.01, and 0.05 M P a at one, three, and 10 months storage time in Manitoba medium grade peat moss. 1 month storage time 3 months storage time 10 months storage time Sample number 0.002 M P a 0.01 M P a 0.05 M P a 0.002 M P a 0.01 M P a 0.05 M P a 0.002 M P a 0.01 M P a 0.05 M P a 6 0.63 0.34 0.37 0.43 0.44 0.41 0.54 0.34 0.33 34 0.59 0.38 0.35 0.46 0.45 0.41 0.41 0.28 0.27 36 0.43 0.37 0.31 0.44 0.43 0.40 0.47 0.38 0.36 37 0.39 0.52 0.36 0.44 0.42 0.41 0.44 0.32 ' 0.32 38 0.52 0.31 0.44 0.41 0.38 0.38 0.46 0.34 0.34 3 0.58 0.34 0.38 0.40 0.38 0.36 0.53 0.35 0.34 35 0.57 0.34 0.40 0.46 0.42 - 0.39 0.45 0.34 0.34 68 0.35 0.35 0.31 0.39 0.39 0.36 0.30 0.29 0.29 Average 0.50 0.37 0.37 0.43 0.41 0.39 0.47 0.34 0.33 St. dev. 0.101 0.062 0.042 0.023 0.024 0.022 0.093 0.038 0.034 64 Table A.16. Water content (cm 3 cm "3) at 0.002, 0.01, and 0.05 M P a at one, three, and 10 months storage time in Alberta medium grade peat moss. 1 month storage time 3 months storage time 10 months storage time Sample number 0.002 M P a 0.01 M P a 0.05 M P a 0.002 M P a 0.01 M P a 0.05 M P a 0.002 M P a 0.01 M P a 0.05 M P a 19 0.63 0.38 0.40 0.34 0.33 0.33 0.53 0.36 0.36 20 0.42 0.46 0.39 0.46 0.48 0.44 0.57 0.42 0.42 42 0.51 0.46 0.48 0.34 0.3.4 0.33 0.55 0.32 0.31 43 0.64 0.41 0.49 0.34 0.34 .0.33 0.58 0.33 0,34 65 0.60 0.37 0.33 0.44 0.43 0.42 0.52 0.28 0.27 67 0.66 0.37 0.40 0.39 0.37 0.38 0.47 0.42 0.40 69 0.61 0.45 0.31 0.40 0.37 0.37 0.45 0.37 0.34 70 0.51 0.37 0.30 0.43 0.41 0.42 0.55 0.32 0.30 71 0.46 0.43 0.38 0.37 0.35 0.34 • 0.56 0.31 0.24 Average 0.56 0.41 0.38 0.38 0.38 0.37 0.53 0.34 0.33 St. dev. 0.088 0.039 0.067 0.045 0.052 0.043 0.044 0.049 0.056 65 Appendix B Figure B . l . Comparison of wet sieving method (1 mm particle size) and dry sieving method (1.18 mm particle size). Samples stored for one month were used (n=36). 66 F i g u r e B.2. Water content determined at 0.002, 0.01, and 0.05 M P a of Manitoba and Alberta medium grade peat moss that were stored for one (a), three (b), and 10 months (c). Error bars represent standard error of the mean (n=9). 0.002 0.01 0 0 5 0 0 0 2 0 0 1 0 0 5 Air pressure (MPa) Air pressure (MPa) 0.002 0.01 0.05 Air pressure (MPa) 67 

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