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

Abstract

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.