Peat Vermiculite Research Articles

483 PB 134 PHYSICAL ANALYSIS OF FRESH AND AGED RICE HULLS USED AS A PEAT MOSS SUBSTITUTE IN GREENHOUSE MEDIA

Rice hulls, a by-product of the rice milling process, were used at various rates to substitute sphagnum peat moss in greenhouse media. Previous studies demonstrated that media containing rice hulls replacing the vermiculite fraction grew plants equal to or better than traditional peat vermiculite blends. The objective of this study was to determine if rice hulls can replace sphagnum peat moss in a greenhouse medium. Physical properties, including bulk density, total pore space, and water retention were determined in media blended with fresh or aged rice hulls, sphagnum peat moss, and vermiculite. The bulk density of the media increased with increasing levels of fresh rice hulls. The pore space in media containing both fresh and aged rice hulls decreased over time during the crop production cycle and the pH increased.

Growth of micropropagated lowbush blueberry with defined fungi in irradiated peat mix

There is an interest in vegetative multiplication of high-yielding clones of Vaccinium angustifolium Ait. to establish or enhance blueberry production. This study evaluates mycorrhizal inoculation as an aid in such propagation from microcuttings. Shoots of Vaccinium angustifolium (clone 7062) generated in vitro were rooted in a peat–vermiculite–perlite substrate with or without ericoid mycorrhizal fungi fortification by Hymenoscyphus ericae or Scytalidium vaccinii and with or without peat sterilization by γ irradiation. Both in irradiated peat mix inoculated with S. vaccinii and in unirradiated peat mix with H. ericae, microcuttings grew taller and branched more than with the four other treatments. The profusely rooted plantlets available from all treatments of the cuttings put on significantly more total length of stems and branches after 167 days in the greenhouse when growing with either inoculant in unirradiated peat than in the unirradiated peat without inoculation. However, the magnitude of difference might be of borderline importance in commercial nursery operations. A higher level of copper and zinc in stem tissue was observed in stem tissue of plants grown with H. ericae with or without irradiation but not with S. vaccinii. Key words: ericoid mycorrhizae, micropropagation, Hymenoscyphus ericae, Scytalidium vaccinii, Vaccinium angustifolium.

Invitro regeneration of plantlets of Canary Island pine (Pinuscanariensis)

A protocol is described for plantlet formation in juvenile tissues of Pinuscanariensis Sweet ex K. Spreng. (Canary Island pine). Adventitious buds were induced on 3-day-old cotyledonary explants cultured on Bornman's MCM medium supplemented with cytokinin. The concentration of benzylaminopurine, the use of other cytokinins alone or in combination with benzylaminopurine, and the concentration of mineral salts strongly affected the bud forming capacity of the cotyledonary explants. Also, the age of the explants significantly influenced the frequency of adventitious bud formation. Bud development was enhanced by the elimination of phytohormones, a reduction of mineral salts and sucrose, and the inclusion of activated charcoal in the medium. The conditions used during the induction phase strongly affected the ability of the induced buds to develop into vigorous rootable shoots. Vitrification problems were eliminated by transferring the shoots to the elongation medium solidified with Gelrite, and shoot remultiplication was enhanced by removing the apical bud. Maximum rooting was obtained by pulsing shoots with a high concentration of indolebutyric acid and by using peat–vermiculite or peat–vermiculite–perlite as substrates. Roots developed within 6–8 weeks, and the regenerated plantlets were transferred to soil under nonsterile conditions, where further development occurred.

Cation exchange capacity of two‐component container media predicted from laboratory analysis of components

Abstract A mathematical equation predicting cation exchange capacity (CEC) of pine bark‐sand container media from CEC of the individual components was formulated. The equation is the weighted sum of milliequivalents contributed by each component and is corrected for shrinkage due to mixing of components. Both measured and predicted CEC increased linearly with increasing percent volumetric bark in pine bark‐sand media. Regression equations describing measured and predicted CEC were not statistically different. The predictive equation was also tested on 6 non‐synthesized 2‐component media prepared from peat moss, perlite, pine bark, vermiculite, and sand. No statistical differences between measured and predicted CEC were obtained.

Evaluation of Composted Sewage Sludge/Straw Mixture for Horticultural Utilization

Collaborative research between Southern Water and Wye College, University of London, has led to the development of a static aerated pile composting process for the treatment of dewatered activated sludge cake/straw mixtures. The process reduces bulk volume of the sludge producing an environmentally acceptable, stabilised, odour and pathogen-free product. Characteristics of the compost make it a suitable general purpose medium for container grown plants, providing the salt concentration is reduced by washing the compost prior to planting. Compared with peat the compost has a higher bulk density, a lower waterholding capacity, a lower cation exchange capacity, a high content of soluble salts, and a higher content of plant nutrients. A compost mixture was successfully developed in the growing trials containing equal quantities of compost, Sphagnum peat, and horticultural vermiculite. The compost has been used successfully to grow a wide range of plants. Plants grown in mixtures based on the compost were in general similar to those grown in peat-based growing media. The compost is a valuable soil conditioner and slow release fertilizer.

Growth and ectomycorrhiza formation of containerized black spruce seedlings as affected by nitrogen fertilization, Inoculum type, and symbiont

Piceamariana (Mill.)B.S.P. seedlings were grown in containers under three levels of nitrogen fertilization (6, 8.5, and 15 mg/seedling per season). Seedlings were inoculated at sowing with Laccariabicolor and Hebelomacylindrosporum, using two methods: mycelial suspension liquid inoculum and peat–vermiculite solid inoculum. Results show that liquid inoculum was as effective as solid inoculum for development of Laccariabicolor ectomycorrhizae on black spruce seedlings. After 20 weeks in the greenhouse, seedlings fertilized with 8.5 mg N and inoculated with L. bicolor had the highest percentage of ectomycorrhizal short roots for both inoculum types, with 59 and 53% for liquid and solid inocula, respectively. These L. bicolor seedlings had significantly more ectomycorrhizae with 8.5 mg N than with 15 mg N. Very few ectomycorrhizae were obtained with Hebelomacylindrosporum for any of the nitrogen levels or either of the inoculum types. There were no significant differences for any growth parameters except shoot/root ratio between L. bicolor seedlings and the controls, regardless of the N level and inoculum type. For both inoculum types, only shoot height of seedlings differed significantly among the three N levels. Seedlings fertilized with 8.5 mg N had root-collar diameter and dry weights that were not significantly less than those that received 15 mg N for both inoculum types. It is only at the lower level of 6 mg N that seedlings inoculated with liquid L. bicolor inoculum absorbed significantly more N than the controls. Analysis of percent N and P concentration in seedlings with the greatest ectomycorrhizal development and analysis of available N and P in their substrate indicated that tissue concentrations of 1.9% N and 0.2% P and substrate fertility of 40 ppm N and 50 ppm P would be appropriate to maintain the ectomycorrhizal association Piceamariana–Laccariabicolor. Salinity in the substrate of control seedlings was generally significantly different between the three N levels during the growing period.

Use of mycelial slurries of mycorrhizal fungi as inoculum for commercial tree seedling nurseries

Blended mycelial slurries of a variety of ectomycorrhizal fungi were assessed for their suitability as inoculum for containerized tree seedlings. Mycelium of most fungi tested, with the exceptions of Pisolithustinctorius (Pers.) Coker & Couch and Paxillusinvolutus (Batsch.: Fr.) Fr., withstood blending well. Viability remained high after storage in modified Melin–Norkrans agar medium, water, or dilute saline at either 4 °C or room temperature, indicating that slurries are robust enough to tolerate conditions that would be encountered in a commercial setting. Experiments investigating methods for applying slurries to containerized seedlings were conducted using Hebelomalongicaudum (Pers.: Fr.) Kummer. Slurry infectivity dropped after it was mixed into a peat–vermiculite growing medium, particularly in the presence of high levels of fertilizer. This indicated that incoculum should not be added to multipots until short roots capable of becoming mycorrhizal are present and that contact of the inoculum with fertilizer should be avoided. Injection of slurry into the root zone resulted in the most consistently high colonization, but application of the slurry to the surface of the growing medium was also effective, the latter being more feasible in a commercial setting. Mycorrhizae developed with as little as 1 mg mycelium per seedling, although 100 mg gave more consistent results. In inoculation trials in which slurries of nine representative fungi were injected into the root zones of 8-week-old black spruce or jack pine seedlings, five of the fungi consistently formed mycorrhizae. For these fungi, slurries could be an effective inoculum.

Increased growth response of plants induced by rhizobacteria antagonistic to soilborne pathogenic fungi

Rhizobacteria applied into pathogen-free soil or peat vermiculite medium, were established in the rhizosphere of plants in population densities of up to 1.9×109 cfu/g. Pseudomonads induced up to 78% bigger roots in tomatoes rooted in water. Pythium-suppressive bacteria increased dry weight of either roots or shoots of tomato, pepper, melon or bean. Fusarium-suppressive bacteria increased emergence of tobacco, cucmber or radish by 10–31% and dry weight by up to 165%. Isolates of the tested bacteria varied in their ability to induce increased emergence and growth of the treated crops.

Interaction of Asparagus Root Filtrate with Fusarium oxysporum f.sp. asparagi

Abstract Asparagus (Asparagus officinalis L.) root filtrate (RF) depressed asparagus seedling emergence in a sterile peat–vermiculite medium. In a medium inoculated with Fusarium oxysporum f. sp. asparagi (FO), the effect was magnified. The response to RF dose, regardless of level of FO infestation, was quadratic. Comparisons with a sucrose solution of the same percentage of soluble solids as the RF suggested that reduced emergence may have been due in part to enhancement of FO growth by the energy source added to the medium. However, after germinating seeds in RF until radicle emergence, then rinsing and transferring them to FO-inoculated medium, emergence was reduced relative to controls. Therefore, depression of emergence apparently related both to an autotoxin somehow predisposing young radicles and/or hypocotyls to increased FO infection and to stimulation of FO in the rhizosphere by the soluble solids content of the root exudate. Infection was confirmed to be the only role of FO: sterilization of the spore suspension by Millipore (0.2 µm) filtration eliminated pathogen toxicity.

Effects of seed covering treatments on the emergence and seedling growth of crisp lettuce drilled with an experimental dibber drill

SUMMARYPelleted seed of the crisp lettuce variety Pennlake was sown on five occasions with units from either the experimental dibber drill designed by the National Institute of Agricultural Engineering or a Stanhay S870 drill. There were three dibber-drill treatments: seeds left in open holes or covered with peat–vermiculite or perlite. Seedling emergence and growth from each sowing of the four drill treatments were compared under different moisture regimes.There were large differences between drill treatments in emergence percentage, time to emergence of 50% of the seedlings which emerged (t50) and seedling weight at all sowings but there was a significant effect of drill treatment on the standard deviation of seedling emergence times at only one sowing. Of the dibber-drill treatments, only very occasionally did open holes or perlite cover give significantly better emergence than peat-vermiculite cover, which gave the most consistent results. In general, the dibber drill with peat-vermiculite cover gave significantly faster and higher emergence and heavier seedlings than the Stanhay drill. Differences in percentage seedling emergence tended to be greater under dry conditions.

Effects of sowing depth on emergence and growth of Douglas-fir, western hemlock, and noble fir seedlings

The effects of sowing depth of seeds of several western forest tree species were studied in greenhouse experiments. Emergence and seedling weight of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), and noble fir (Abiesprocera Rehd.) were reduced by sowing seeds in soil at depths greater than 1 cm. Deep sowing in a peat–vermiculite mixture also reduced the emergence of Douglas-fir and western hemlock, but increased the hypocotyl diameters and weights of Douglas-fir seedlings.

The influence of rhizome features on subsequent regenerative capacity in speargrass ( Imperata cylindrica (L.) Beauv.)

Studies conducted with the rhizomes of speargrass ( Imperata cylindrica (L.) Beauv.) in a growth-chamber environment using a peat—vermiculite medium showed that the stage of rhizome growth and its weight were the main features determining the regenerative capacity of the propagule. Re-growth ability increased with rhizome age and weight, whereas rhizome length, thickness and number of buds did not contribute significantly towards subsequent growth. On the basis of regenerative capacity, speargrass rhizomes were classified into young, intermediate, mature and old rhizomes.

THE DEVELOPMENT AND ULTRASTRUCTURE OF ECTOMYCORRHIZAS

SummaryThe development of ectomycorrhizas of pine was followed experimentally using either sterile peat–vermiculite with nutrient solution or natural non‐sterile field soil. Roots were harvested sequentially and comparative analyses of their ultrastructure were obtained. Hartig net formation is initiated before the formation of a compact sheath in both types of synthesis but, while the net formed after 3 weeks in sterile culture and was complete after 6 and 8 weeks, in non‐sterile soil its initiation was delayed until 11 weeks and it had reached a depth of only one cortical cell after 19 weeks. While differences in gross morphology of mycorrhizas can be recognized, the structure of the host–fungus interface in the Hartig net region is comparable in mycorrhizas formed with different soils or different isolates. In the young Hartig net, separate host and fungal cell walls are distinguishable, while in the mature net they lose their integrity. No marked change of structure is observed within the cortical cells adjacent to the Hartig net and their organization is similar to that of cortical cells of non‐mycorrhizal lateral roots. The development and structure of the host–fungus interface is discussed in relation to its possible function.

Production of ectomycorrhizae on container-grown jack pine seedlings

Jack pine (Pinusbanksiana Lamb.) seedlings were grown for 20 weeks in a peat–vermiculite medium inoculated with solid carrier mycelial inoculum. The low fertilizer levels used resulted in seedling sizes below standard for outplanting but permitted mycorrhizal development by 9 of the 12 fungi tested. Greater than 90% of the short roots were infected when seedlings were inoculated with Thelephoraterrestris Ehrhart ex Fr., Laccariaproximo Boudier, Hebeloma sp., or E strain. About half the short roots were infected when Cenococcumgeophilum Fr., Pisolithustinctorius (Pers.) Coker & Couch, and Astraeushygrometricus (Pers.) Morgan were used. Thirty-two and 17% of the short roots were infected by Lactariusparadoxus Beardslee & Burlingham and Sphaerosporellabrunnea (Alb. & Schw. ex Fr.) Svrcek & Kubicka, respectively. Inoculation with Amphinemabyssoides (Fr.) J. Erikss., Hydnumimbricatum L. ex Fr., and Tricholomaflavovirens (Pers. ex Fr.) Lundell resulted in no infection.

Performance of germinated, imbibed and dry petunia seed fluid-drilled in two gels with nutrient additives

Seeds of ‘Commanche’ petunia ( Petunia hybrida Vilm.) were germinated (GE) or imbibed (IM) on the surface of Laponite 445 or Natrosol 250 HHR gels prepared from 0, 0.5 or 1.0-fold Hoagland's solution. These seeds and dry seed (DS) were incorporated in the gels and extruded onto peat—vermiculite. When compared to a dry-seed control (without gels), DS in either gel without nutrient additive did not increase percentage of transplantable seedlings, but IM and GE resulted in a 32% increase. In comparing only fluid-drilled treatments, percentage of transplantable seedlings was increased by GE relative to IM in both gels, but by IM relative to DS only in Laponite. In both gels, emergence rate ( T 50) and uniformity ( T 10–90) and shoot fresh weight were influenced in the order GE > IM > DS. Increasing nutrient concentration in both gels decreased T 10–90 but had no effect on T 50 or shoot fresh weight. Percentage of transplantable seedlings was increased in Laponite but decreased in Natrosol with increasing gel nutrient concentration. The highest percentage of transplantable seedlings was achieved with GE in Natrosol without nutrient additive (75.4%) and in Laponite with the highest nutrient concentration (81%), each giving approximately one-half of the T 50 and T 10–90 values of the dry-seed control which yielded 53% transplantable seedlings.

Effects of Preplant Phosphorus Fertilization Rate and of Nitrate and Ammonium Liquid Feeds on Tomato Grown in Peat–Vermiculite

Abstract The effects of 0.02, 0.06, 0.18, and 0.54 kg P/m3 incorporation as superphosphate (0-9-0) in peat–vermiculite and of NO3-N and NH4-H liquid feeds were investigated with tomato (Lycopersicon esculentum Mill. cv. Marglobe). Increasing P rate decreased shoot and root dry weights but increased total fruit fresh weight. NH4-N, relative to NO3-N nutrition, decreased shoot growth but had no effect on fruit yield. Decreased vegetative growth with increasing P rate and NH4-N nutrition was associated with decreased leaflet xylem pressure potential, increased transpiration rate, and increased leaf NH4-N concentration. Leaf P and medium water-soluble P concentrations increased with increasing P rate but were unaffected by N form. During time of fruit development, leaf P content decreased at the 2 lowest P rates but increased at higher P rates. Net P export from leaves ceased and luxury P consumption began between 0.06 and 0.18 kg P/m3.

Transplant Quality, Yield, and Heavy-Metal Accumulation of Tomato, Muskmelon, and Cabbage Grown in Media Containing Sewage Sludge Compost1

Abstract Transplant quality, as measured by height and dry weight, of cabbage (Brassica oleracea L. Capitata group) and tomato (Lycopersicon esculentum Mill.) was lower for plants grown in media containing sewage sludge compost with a high heavy-metal concentration (HM) than for plants grown in peat-vermiculite (P-V) or low-metal (LM) sewage sludge compost media. Compost source had no significant effect on transplant quality of muskmelon (Cucumis melo L.) seedlings. Marketable yield of cabbage, tomato, or muskmelon was similar regardless of the media used to grow the transplants. The concentration of Zn, Cu, Mn, Ni, and Cd were significantly higher in transplants grown in HM media than in those grown in LM media. With the exception of Cd, metal levels in transplants grown in LM media were similar to those grown in P-V. Transplant media had little influence on the heavy-metal concentrations found in either foliar samples or the edible portions of the crops studied. Heavy-metal concentrations in foliar samples of all 3 crops were lower than those found in transplants. The lowest concentrations were found in tomato and muskmelon fruit, and in cabbage heads. The Cd concentrations in edible portions were very low regardless of the source of compost in the transplant media, indicating that sewage sludge composts, particularly those low in heavy metals, can be used safely in the growing media of vegetable transplants.

Efficacité en pépinière forestière d'un inoculum de champignon ectomycorhizien produit en fermenteur et inclus dans une matrice de polymères

Pure culture inocula of ectomycorrhizal fungi are usually produced on a vermiculite peat mixture. They can also be prepared by cultivating the fungus in a fermentor and entrapping it in a polymeric gel as proposed by Dommergues et al. (1979) for bacteria and Jung et al. (1981) for different microorganisms. We have prepared different types of inoculum of Hebeloma cylindrosporum as follows: non washed peat vermiculite inoculum; washed peat vermiculite inoculum; pellets of mycelium cultivated in a fermentor of 800 liters; pellets of mycelium cultivated in a fermentor and included in an alginate gel; pellets of mycelium cultivated in a fermentor, included in an alginate gel and mixed with macropourous silica; pellets of mycelium cultivated in a fermentor, included in a gel of xanthane and 1-4 galactomannan (caroube gel) and mixed with macropourous silica. These different types of inoculum have been tested with spruce (Picea exelsa) and douglas fir (Pseudotsuga douglasii) in fumigated and non fumigated nursery soil. In non fumigated soil it is impossible to obtain a good mycorrhizal development by Hebeloma cylindrosporum with any of the above types of inoculum. In fumigated soil we have obtained a good mycorrhizal development of the two species with Hebeloma cylindrosporum. The mycelium entrapped in the three types of polymers (alginate, alginate and macropourous silica, xanthane, galactomannan and macropourous silica) is a better inoculum than the non entrapped mycelium or the mycelium produced on peat and vermiculite. This method of producing mycelium of an ectomycorrhizal fungus in fermentor and entrapping it in a polymeric gel seems to be a suitable way for producing large quantities of commercial inoculum

Transplant Quality and Metal Concentrations in Vegetable Transplants Grown in Media Containing Sewage Sludge Compost1

Abstract Tomato (Lycopericon esculentum Mill.) and cabbage (Brassica oleracea L. Capitata group) transplants were grown in peat-vermiculite (P-V) or in media containing sewage sludge compost from either a residential, low metal (LM) or industrially contaminated, high metal (HM) source. The transplant quality (stem diameter, fresh, and dry weight) of plants grown in P-V and LM were similar. Transplants grown in HM media were small, less-developed, and exhibited symptoms of heavy metal phytotoxicity. The concentrations of Zn, Fe, Mn, Cu, Pb, Cd, and Ni in tomato and of Zn, Cu, Cd, and Ni in cabbage plants grown in HM media were significantly higher than those in transplants grown in LM media. The addition of peatmoss to LM media had little influence on media pH or the heavy metal concentrations in transplants. However, peatmoss lowered the pH of HM media and thus the concentrations of Zn, Mn, Cu, and Ni in tomato and Zn and Mn in cabbage transplants increased. Concentrations of Zn and Cu in tomatoes and Zn in cabbage were above phytotoxic levels.

Copper requirements of container-grown conifer seedlings

Blue spruce (Piceapungens Engelm.), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco, Noble fir (Abiesprocera Rehd.), and eastern white pine (Pinusstrobus L.) seedlings grown in the greenhouse in peat–vermiculite medium were fertilized with nutrient solutions containing 0.00–0.64 ppm Cu. Maximum growth generally occurred at levels higher than the conventional fertilizer rates of 0.02–0.06 ppm, particularly for Douglas-fir, with subsequent shoot or needle concentrations of 3 or more ppm. Optimum growth of Douglas-fir in a peat–vermiculite medium treated with a single initial drench of 0–100 ppm Cu/L mix occurred over a broad range of foliar Cu concentrations greater than 4 ppm. Supplemental Cu for container-grown conifers thus appears necessary in some cases, but not harmful in others.