SOIL LIME LEVEL (PH) AND VA-MYCORRHIZA EFFECTS ON GROWTH-RESPONSES OF SWEETGUM SEEDLINGS

Effects and interactions of soil liming, soil horizon, and two endomycorrhizal fungus species on the growth of sweetgum (Liquidambar styraciflua L.) were studied in sequential greenhouse experiments. The strongly acid surface A1 [8.87% organic matter (OM)] and subsurface C (0.10% OM) horizons of P-deficient Jory clay loam (Xeric Haplohumult) were limed with increments in CaCO3 to attain a range in soil pH from 5.0 to 8.1. In the absence of vesicular-arbuscular mycorrhizae (VAM), neither the organic matter-rich surface nor the organic matter-poor subsurface horizon supported growth of sweetgum seedlings at any pH, despite regular (biweekly to weekly) supplements of P-shorted Long Ashton's complete nutrient solution. Under the same cultural regime, two species of the Glomus VAM family strikingly enhanced sweetgum growth (as measured by stem height and collar diameter, leaf number and area, and tissue dry weight) but to different degrees depending on apparent pH tolerance of the VAM species. Glomus fasciculatum, with about 40% root colonization, stimulated the earliest (within 4 to 6 weeks) and largest growth response at the lower pHs (5.1 and 5.9). Conversely, Glomus mosseae with © 1983 Soil Science Society of America.