Nursery Soil Research Articles

Influence of humic-rich organic amendments to coniferous nursery soils on Douglas-fir growth, damping-off and associated soil microorganisms

Fusarium spp are absent from coniferous forest soils, yet are conspicous in conifer nursery soils. To test the hypothesis that loss of humus from nursery soils may affect Fusarium spp survival, three nursery soils were amended with four concentrations of three organic materials high in humic content. Amendment-induced increases and occasional decreases in tree growth varied with soil origin. A humic-rich amendment that stimulated tree growth in all soils also increased the numbers of several soil microbial groups (“total” bacteria, actinomycetes, extracellular-chitinase producers and facultative anaerobes). Fusarium-induced damping-off was reduced in one of the three soils by all amendments. Ectomycorrhizae were increased by only one type of amendment and then in only one of the soils. The complex nature of soil-humic interactions and the physiological action of these substances on roots and microbial cells complicates predicting the efficacy of humic-rich amendments to nursery soils.

Response of nursery soil microbial populations to volatiles purged from soil around Douglas-fir ectomycorrhizae

Ectomycorrhizae produce biologically-active volatile compounds in vitro. Although the microbial populations in the soil surrounding ectomycorrhizae are known to differ quantitatively and qualitatively from those in the soil surrounding nonmycorrhizal roots, it is not known whether volatiles contribute to this difference. An apparatus which slowly purges volatiles from a “donor” test soil into a “receiver” soil was used to determined the effect of volatiles from pasteurized “donor” soils containing ectomycorrhizal Douglas-fir seedlings on Fusarium and other microbial populations of a “receiver” nursery soil. Seedlings which were ectomycorrhizal with Laccaria toccata or a Hebeloma sp., produced volatiles which significantly increased bacterial populations in receiver soils. The populations of actinomycetes, Fusarium extracellular chitinase producers, facultative anaerobes and phosphate-solubilizing bacteria were not significantly influenced by volatiles from ectomycorrhizal seedlings compared to those from nonmycorrhizal seedlings. Factors which may influence the quantity and quality of volatiles produced by an ectomycorrhizal seedling and the consequent effect on microbial populations in the ectomycorrhizosphere are discussed.

Rotylenchus Robustus in a Pinus Radiata Nursery in Victoria.

Small patches of Pinus radiata seedlings growing in light, sandy, nursery soils at Rennick in south-western Victoria turned chlorotic; many seedlings were stunted and a few died. Symptoms were associated with a heavy infestation of Rotylenchus robustus in roots and soil. This is believed to be a new record of R. robustus on P. radiata in Australasia.

Population Dynamics and Survival of Xanthomonas campestris in Soil in Citrus Nurseries in Maryland and Argentina

Fluctuations in soil populations were correlated with rainfall, soil moisture, and air temperature, as well as leaf populations. After the removal of infested plants to simulate eradication. Xdd-A could not be recovered after 21 days from either nursery site. It appears Xcc-A and Xc have very survival capability in subtropical soils

Recovery and Pathogenicity of Rhizoctonia solani and Binucleate Rhizoctonia-like Fungi in Forest Nurseries

A baiting technique using slash pine stem segments provided a rapid, sensitive, and accurate means of assessing inoculum potential of populations of Rhizoctonia solani and binucleate Rhizoctonia-like funi (BRLF) in forest nursery soils. Recovery of R. solani and BRLF from soils was best when stem segments were from 45-to 75-day-old seedlings and when soil plates with stem segments were incubated for 48 hr at 20-30 C

Torphological and physiological changes in ectomycorrhizas of spruce [Picea excelsa (Lam.) Link] associated with ageing

summaryEctomycorrhizas of four‐year‐old Picea excelsa (Lam.) Link seedlings, grown in nursery soil, are described. The main ectomycorrhiza type, occurring on 55–80% of the root apices, exhibited a normal sheath. The associated symbiotic fungus probably belonged to the Hebeloma genus. Behind these extomycorrhizal root lips, older ectomycorrhizas were observed and the apical ones presumably originated from those. One‐ and two‐year‐old ectomycorrhizas lacked sheaths, but a normal Hartig net could be observed in transverse sections. The metabolic‐activity of these older ectomycorrhizas, as measured by radiorespirometry of [14C]glucose, was reduced compared to the younger symbiotic organs. This glucose respiration was, however, still larger than the activity of non‐mycorrhizal exploratory roots. The mechanism of sheath loss and its significance as an ageing process are discussed.

Distribution of Fusarium Species in Sections Roseum, Arthrosporiella, Gibbosum and Discolor Recovered from Grassland, Pasture and Pine Nursery Soils of Eastern Australia

Fusarium species in sections Roseum, Arthrosporiella, Gibbosum, and Discolor were common in grassland, pasture, and pine nursery soils of eastern Australia. The grasslands consisted of grazing lands, i.e., communities of native plants that were grazed or browsed, and pastures, i.e., communities consisting predominantly of introduced species whether sown or volunteer. In this study, eastern Australia was divided into three zones showing climatic changes from north to south. The northern zone represented a tropical area, the middle zone represented a tropical to subtropical area and the southern zone represented a temperate area. Fusarium acuminatum, F. avenaceum, F. compactum, F. crookwellense, F. culmorum, F. equiseti, F. graminearum, F. graminum, F. heterosporum, F. longipes, F. reticulatum, F. sambucinum, F. scirpi, F. semitectum and an unidentified population were recovered.

Distribution of Fusarium Species in Sections Roseum, Arthrosporiella, Gibbosum and Discolor Recovered from Grassland, Pasture and Pine Nursery Soils of Eastern Australia

Fusarium species in sections Roseum, Arthrosporiella, Gibbosum, and Discolor were common in grassland, pasture, and pine nursery soils of eastern Australia. The grasslands consisted of grazing land...

Comparative effectivity of three Fraxinus pennsylvanica Marsh, vesicular‐arbuscular mycorrhizal fungi in a high‐phosphorus nursery soil

SUMMARYInoculation of seedlings of green ash (Fraxinus pennsylvanica Marsh.) with vesicular‐arbuscular (YA) mycorrhizal fungi, significantly increased seedling heights, root collar diameters, dry matter accumulations and phosphorus (P) nutrition relative to control seedlings. The ability of these YA mycorrhizal fungi, which were isolated from low‐P forest soils (5–7 mg kg−1), to enhance seedling growth in a high‐P (148 mg kg−1) nursery soil provides evidence for the occurrence of YA mycorrhizal fungi which may be effective under both high and low soil P conditions. There was a significant positive correlation between foliar P concentration and percentage infection. Despite significant differences in tissue P concentrations among seedlings receiving different inoculum treatments, the degree of growth enhancement was the same. Growth increases due to enhanced P nutrition in seedlings with higher concentrations of foliar P may have been offset by an increased drain on host photosynthate via production and maintenance of greater amounts of fungal bomass, or may have been limited by the low K fertility of the nursery soil.Colonization percentages in roots of seedlings of green ash were high despite high soil P concentrations. The pattern of infection development was unique for each YA mycorrhizal fungal species. A modification of the grid‐line intercept technique was used to assess intensity of infection. Infection for all endophytes during the period of most rapid vegetative host growth was predominantly arbuscular. However, arbuscular intensity fluctuated during this period. Vesicles increased in number with time but always made up a small percentage of total infection.

Management of forest nursery soils dominated by calcium salts

Soils that contain high levels of calcium salts can affect tree seedling growth in two ways: high total salts can reduce water availability, and excess calcium can affect seedling nutrition. Nutritional problems, such as iron deficiency (“lime-induced chlorosis”) and phosphorus deficiency, can seriously affect forest nursery production through growth losses, stunting, and sometimes seedling mortality. High calcium soils can be diagnosed by visible symptoms, soil tests, and seedling nutrient analysis. Soil management practices that have been used to treat high calcium soils include site selection and soil mapping, species and stock type selection, fertilization, and soil acidification. Cultural practices, including irrigation, mulching, deep ripping, organic matter amendments, and mycorrhizal treatments, have been used to lessen the adverse affects of high calcium soils.

Viability of an ectomycorrhizal inoculum produced in a liquid medium and entrapped in a calcium alginate gel

Survival of Hebeloma crustuliniforme (Bulliard ex Fries) Quelet, grown in a liquid medium and subsequently entrapped in beads of calcium alginate, was tested under different conditions. Mycelium viability was not affected either by curing the beads for up to 22 h in 0.7 M CaCl2 or by the addition of either peat or bentonite to the alginate gel. Both peat and bentonite improved the water retention of the alginate gel, but only the incorporation of bentonite slowed down the rate at which moisture was lost by evaporation. At 4 °C the entrapped mycelium retained its viability for at least 5 months, provided that storage conditions remained humid. Partial drying of the beads reduced the effective storage time to a month. Emergence of hyphae from the beads was influenced by the presence of sterile soil extracts prepared from a podzolic soil, an acid brown earth, a mesotrophic brown earth, an eutrophic brown earth, and a rendzina. Hyphae grew out of all the beads containing peat irrespective of the type of soil extract but only grew out of those containing bentonite when they were on the mesotrophic brown earth extract. Hyphal emergence from beads containing neither peat nor bentonite appeared to be influenced by the pH of the extract, being better on those that were more acidic. Both sterile and nonsterile nursery soil supported growth of hyphae from the three types of bead, but on nonsterile soil, hyphae were not abundant and those that developed began to die off sooner than those on sterile soil.

Results of seven years of biological control of Agrobacterium tumefaciens in Spain1

Biological control of Agrobacterium tumefaciens using the K84 strain of A. radiobacter has been practised in Spain since 1979. Strain K84 is produced in Sevilla by the Agricultural Research Service and is mixed with peat. This formulation is authorized for use on stone fruits and roses, since results of various trials on rootstocks of these crops have shown that K84 is effective in controlling the disease in naturally infected nursery soil, as well as in experimental tests carried out on artificially inoculated soil. Results of biological control trials have shown that K84 has some effect on A. tumefaciens strains resistant to agrocin 84. Factors other than susceptibility to agrocin 84 influence the efficacy of biological control. This was demonstrated by using a K84 agrocin non‐producer strain which proved effective against both resistant and susceptible strains. Biological control on apple or pear is not yet authorized in Spain due to a paucity of data on field trials. However, initial pot tests showed good K84 activity on these hosts, against Spanish strains of A. tumefaciens. On grapevine, most of the A. tumefaciens strains that were isolated belong to biotype 3 and are resistant to agrocin 84. Because the disease is systemic on this species the use of K84 is not authorized.

Populations of Agrobacterium in Vineyard and Nonvineyard Soils and Grape Roots in Vineyards and Nurseries

Populations of Agrobacterium in Vineyard and Nonvineyard Soils and Grape Roots in Vineyards and Nurseries

Organic matter amendments to a calcareous forest nursery soil

Organic amendments were added to a southwestern United States forest nursery sandy loam soil to determine the effects on soil nutrient reserves and subsequent growth of 1.5+0 ponderosa pine (Pinus ponderosa Laws.) seedlings. Treatments included irradiated sewage sludge, peat moss and pine bark each at 67 t/ha, sawdust at 43 t/ha, and a control that received no organic matter. Sludge caused immediate increases in soil nutrients, especially N and P. Sawdust resulted in near complete N immobilization 45 d after application. Peat moss and bark did not significantly alter soil nutrients. All treatment effects disappeared within 6 months of application.

Sweetgum Seedling Growth and Vesicular‐arbuscular Mycorrhizal Development as Affected by Soil Fumigation

AbstractThe effects of soil fumigation with methyl bromide (390 kg/ha) on sweetgum (Liquidambar styraciflua L.) seedling height, root collar diameter, root morphology, vesicular‐arbuscular mycorrhizal (VAM) infection, soil‐borne spore number, and soil fertility were monitored from seeding in the nursery until lifting. Seedlings in nonfumigated soil had greater heights, root collar diameters, and VAM infection than seedlings grown in fumigated soil. Differences between fumigation treatments were statistically significant for root collar diameter and VAM infection between 92 and 131 d after seeding, and for VAM infection after 320 d (lifting). Soil‐borne spore number increased markedly between 92 and 176 d after seeding but no significant difference between soil fumigation treatments was detected. Soil fertility was not significantly affected by soil fumigation. At lifting, seedlings were graded into large (≥7.6 mm) and small (≤6.9 mm) root collar diameter classes within each soil fumigation treatment and outplanted. Height and diameter growth differences between seedlings lifted from fumigated or nonfumigated soil were not significant after one growing season in the field. However, root collar diameter of seedlings from nonfumigated nursery soil was larger than that of seedlings from fumigated nursery soil after one growing season. Glomus fasciculatum (Thaxt. sensu Gerd.) Gerdemann and Trappe was indigenous to both the nursery and outplanting site.

The Association of Thelephora Terrestris with Arbutus X Andrachnoides

"The Association of Thelephora Terrestris with Arbutus X Andrachnoides." Mycologia, 78(4), pp. 683–684Key Words: Thelephora terrestrisarbutoidmycorrhizae

Response of Citrus Seedlings to Various Field Inoculation Methods with Glomus deserticola in Fumigated Nursery Soils

Abstract Broadcasting, banding, and drilling were more effective in the field inoculation of plants with the vesicular arbuscular mycorrhizal fungus, Glomus deserticola Trappe, Bloss and Menge than seed inoculation or the application of lyophilized roots to both direct-seeded and transplanted citrus seedlings. Mechanized field inoculation of direct seeded and transplanted citrus seedlings is feasible, using fertilizer banding equipment, and seeding machines. In oculum remained consistently infective after soil inoculation for up to 2.5 months in fumigated field soil and for up to 1.5 months in mycorrhizal pot cultures of citrus grown in the greenhouse.

Development of vesicular–arbuscular mycorrhizae in a young sweetgum plantation

Sweetgum seedlings with vesicular–arbuscular mycorrhizae formed by Glomusetunicatum or Glomusdeserticola in nursery soil with 30 ppm available phosphorus (P) and nonmycorrhizal seedlings grown in nursery soil with 800 ppm available P were outplanted and whole trees were excavated periodically over the next 5 years in the plantation to follow mycorrhizal development. Four months after outplanting, roots of all initially nonmycorrhizal seedlings had formed vesicular–arbuscular mycorrhizae and the degree of root colonization was comparable to that of initially vesicular–arbuscular mycorrhizal seedlings. New feeder roots did not develop on seedlings of any treatment until almost 5 months after planting. By the end of the first growing season and for the remainder of the study, vesicular–arbuscular mycorrhizae development was approximately the same on all seedlings. The proportion of feeder roots colonized by vesicular–arbuscular mycorrhizal fungi stabilized at 65 to 70%; approximately 56% of the cortical tissues of all feeder roots were colonized with arbuscles, vesicles, and hyphae. Periodic assays of the soil in the plantation showed that vesicular–arbuscular mycorrhizal fungal spores gradually declined from an initial high of 3600 spores to 620 spores per 100-cm3 soil sample after 5 years. This decline was probably caused by crown closure of the sweetgum trees which gradually suppressed understory vegetation.

Pratylenchus penetrans(root lesion nematode)—cause of patch chlorosis ofPinus radiataseedlings

Summary The root lesion nematode Pratylenchus penetrans was recovered from the roots of stunted, chlorotic, wilting and recently dead Pinus radiata seedlings growing in a forest nursery located on deep sands in south-western Victoria adjacent to the South Australian border. Although specimens of the genus Pratylenchus were recovered from P. radiata nursery soils in this region about 20 years ago, this is the first record of the species P. penetrans parasitising P. radiata in Australia. Greenhouse and phytotron tests showed that P. penetrans could, by itself, cause the disease symptoms observed in the nursery and that other soil pathogens, which produce similar symptoms, contributed insignificantly. P. penetrans was controlled by a single application of readily available proprietary brands of either liquid or granular nematicides shortly after seedling germination. A 10–15% improvement in seedling height was obtained even in healthy-looking seedlings infested with nematodes.

Growth and ectomycorrhizal development of Pinus caribaea seedlings inoculated with basidiospores of Scleroderma dictyosporum in fertilized nursery soil in Tanzania

Seeds of Pinus caribaea were sown in plastic pots containing nursery soil with or without a basidiospore inoculum of Scleroderma dictyosporum. After seedling establishment, five fertilizer treatments involving 0, 250, 500, 750 and 1000 g NPK per m 3 of nursery soil were administered. The ratio of N:P:K in NPK was 3:3:1. Basidiospores of S. dictyosporum were an effective inoculum for P. caribaea seedlings. Inoculated seedlings showed superior growth in height, root collar area, length of stem with needles and dry matter production. Inoculation also increased the concentration of P in the plant tissues but had no effect on other nutrients studied. Fertilizer response was evident, but there were generally no benefits of using fertilizer levels above 250 g NPK per m 3 soil. In fact, mycorrhizal development was progressively reduced with each increase in the level of NPK fertilizer. Tissue Mg concentrations were also deficient, a reflection of nutrient uptake imbalance due to high concentrations of ammonium sulphate and potassium chloride in the soil. Basidiospores of S. dictyosporum can therefore be used for routine inoculation of P. caribaea seedlings in nursery soils at low levels of NPK. Coincidentally such a reduction in the amount of NPK applied in nursery soil will have both biological as well as economic benefits.