Inoculation of seedlings at the time of field planting is time consuming, requires more inoculum, and the introduced fungus must be compatible with native microorganisms and climatic conditions of the planting site (Riffle and Maronek 1982). Thus, nursery inoculated seedlings are more frequently outplanted (Roldan et al. 1996; Garbaye and Churin 1997; Nunez et al. 2006; Rincon et al. 2007) than inoculated at the time or after field planting. Castellano (1996) reviewed most of available literature (including unpublished data) on outplanting performance of ECM-inoculated seedlings and provided insight to the fungus-inoculum type-host-location combinations in field experiments. Inoculum types and application methods in the field are very similar to nursery inoculation of container-grown seedlings. Various natural organic materials and organic wastes are often used and may be considered as a simple source of ECM fungi propagules. Hallsby (1995) planted Norway spruce seedlings to mounds containing forest floor material from the F- and H-layers. Querejeta et al. (1998) added 150 ml of pine forest soil (top 20 cm of mineral soil) to the planting holes of Pinus halepensis seedlings at the time of planting. Organic materials, particularly decayed wood or mixtures containing decayed wood were equal or superior to mineral substrates for supporting ECM activity on planted seedlings (Harvey et al. 1997). Larcheveque et al. (2006) incorporated fresh co-composted sewage sludge and greenwastes (20 or 40 kg.m~2 of compost) into the soil at each stem of 1-year-old seedlings of Quercus ilex, Pinus halepensis, and P. pinea.
In field experiments with laboratory produced inoculum, e.g., Baum et al. (2002) applied 50 ml of alginate beads containing mycelium of Laccaria laccata around each Populus trichocarpa cutting (1.5-m long annual shoots, diameter 13-17 mm) in 50-mm soil depth. Dunabeitia et al. (2004) inoculated seedlings few days after outplanting (and reinoculated 5 months later) by watering at 5 cm around the stem with 200 ml of spore slurry of Scleroderma citrinum, Pisolithus arhizus, and Leccinum scabrum. Menkis et al. (2007) wrapped root systems of Pinus sylvestris and Picea abies seedlings in a filter paper containing mycelium of Cenococcum geophilum, Piceirhiza bicolorata or Hebeloma crustuliniforme, overlaid with damp peat-sand mixture, wrapped in a paper towel, and planted seedlings on poor sandy soil.
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