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The objectives of this study were to determine if the use of leonardite as a fertilizer supplement improved crop growth and if there was a residual effect from previous applications. Three planting sequences were established and leonardite applied at 0, 50, 100, 200, and 400 lb/acre (0, 56.1, 112.1, 224.3 and 445.6 kg·ha−1). Subplots were treated at the first, the first and second, or all at three planting sequences. `Purple Top White Globe' turnip (Brassica rapa L.) and `Florida Broadleaf' mustard greens (Brassica hirta L.) were used as the indicator crops in the first two and last sequences, respectively. No differences in plant growth were observed among number of applications or treatment rate. Differences in soil potassium and iron were observed.

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Formation of arbuscular mycorrhizae (AM) has been inhibited in soilless potting mixes that usually contain some proportion of peat moss. The cause of the inhibition has been thought to be high fertilizer P content in the media that suppresses spread of the fungal symbiont in the root tissue. However, there has also been some suggestion that the peats themselves may contribute to the inhibition. That possibility was explored in this study. A sandy-loam soil, in which mycorrhizae consistently enhance plant growth under P-limiting conditions, was amended with six different peats. Onions (Allium cepa 'White Lisbon'), as an indicator host, were grown in the mixes under P-limiting conditions, and were inoculated or not with the AM fungi Glomus deserticola or Gigaspora rosea. Plant growth response to inoculation with AM fungi (AMF) varied with the type of peat and AMF isolate. Inoculated plants generally had the highest root biomass when grown in soil amended with peat. Root colonization by the two fungal symbionts was also affected differently by different peat amendments. Root colonization by Glomus deserticola and Gigaspora rosea was inhibited by at least half of the peat types. However, the types of peat inhibitory to Gigaspora rosea colonization were not the same as those inhibitory to Glomus deserticola colonization. These results indicate that different peat amendments can suppress or enhance mycorrhiza formation on onion roots and resultant growth benefit under P-limiting conditions, depending on the mycorrhizal fungus used.

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treatments resulted in a significant aerial biomass growth enhancement that reached the average value of 95.7 mg/plant with no statistical difference among the three application rates. Daughter plants originating from nodes excised at 8 WAT did not show

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Composted materials with high humic and microbial content, and their water extracts, are increasingly used in the nursery industry as potting mix components or as liquid amendments for the purposes of enhancing plant growth. Common speculation is that such materials either contain beneficial microbes or stimulate those in or added to the medium, such as vesicular-arbuscular mycorrhizal (VAM) fungi, known to have growth-stimulating effects on plants. Experiments were conducted to determine if one such compost enhanced plant growth by stimulating VAM fungi or other growth-enhancing microbes, by simply providing limiting nutrients [phosphorus (P)], or a combination of the two. Highly mycorrhiza-responsive onion (Allium cepa) `White Lisbon' was used to evaluate the interactions of composted grape pomace (CGP), the VAM fungus Glomus intraradices, and preplant soil heat treatment on onion growth under P-limiting conditions. CGP and its water extract stimulated onion growth under P-limiting conditions in the absence of VAM; the extract was more effective than the granular CGP. Growth was enhanced further by addition of G. intraradices, and the extract enhanced its colonization of roots. Heat pretreatment of the soil inconsistently affected growth-enhancement by CGP or its extract. Thus, inoculating plant roots with mycorrhizal fungi in combination with this composted organic amendment or its extract was beneficial. The effect could have been due to the CGP providing a source of P to overcome the P-limiting conditions, and to the mycorrhizal fungus enhancing P uptake by its extraradical hyphae and thereby increasing nutrient-use efficiency.

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Coconut fiber dust (coir) is being used as a peat substitute or amendment to potting mixes with varied results. However, its microbial composition and compatibility with beneficial microbes that might be added to growth media in the nursery, such as mycorrhizal fungi, has not been determined. In this study, coir was amended to a peat-based medium (15%, 30%, 45%, and 60% by volume) to determine its effects on growth of several ornamental plants and on the formation and function of the arbuscular mycorrhizal (AM) fungus Glomus intraradices. Mycorrhizae formed as well, and usually better, in all the coir-amended peat treatments as in peat alone. The magnitude of growth enhancement due to mycorrhizae was small for the plants tested in these media compared to that which usually occurs in soil-based media. In this experiment, plant growth responses appeared to be independent of level of mycorrhizal colonization and were plant species dependent. Consistent growth enhancement from mycorrhizae only occurred with marigold (Tagetes patula). With germander (Teucrium fruticans), growth was depressed with mycorrhizal inoculation in the medium composed of 60% coir. Growth of lavender (Lavandula augustifolia) was depressed in all coir-amended media, with or without AM inoculation, compared to the nonamended control. These results confirm previous reports of varied response of plant species to coir, and indicate the lack of any detrimental effects of coir on mycorrhiza formation.

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rates produced significant reductions in stolon length. The number of nodes per stolon was not affected by treatments and no effect was observed in node vitality, while daughter plants showed a post inhibition growth enhancement when nodes were excised

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comprised the majority of seedling tree weight after year 1 ( Fig. 3 ). This suggests that although no aboveground growth effects were observed for cultivars in the year of transplant, aldicarb could have affected root growth, enhancing above ground growth

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VC could provide predictable physical properties when blended with other substrate components. Changes in physical properties can result in growth enhancement or inhibition; therefore, additional studies must be conducted to determine optimal mix

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lycopersicum ( Colla et al., 2014 ; Parrado et al., 2008 )], radish [ Raphanus sativus ( Liu et al., 2008 )], and lily [ Lilium ( De Lucia and Vecchietti, 2012 )]. The growth enhancement by PHs has been attributed to increased nutrient uptake, assimilation

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canopy size among irrigated species. An irrigation regime × MAT interaction occurred for three native and three nonnative species in year 1, showing that the growth-enhancing effect of irrigation increased with time ( P < 0.01). Canopy sizes of the

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