Comparative growth responses to perennial forage legumes in hill-land ultisols and their relationship to soil acidity-related factors

As soils of humid, temperate hill-lands are typically highly weathered, mineral, and acidic, forage legumes for these conditions need to be evaluated, and limiting soil acidity-related factors determined. Two ultisol topsoils (0-15 cm) from Appalachian hill-lands of the Lily series (Typic Hapludults) were utilized in a growth chamber experiment. Both soils were of similar pH and low in fertility but different in % base saturation due to different management histories (abandoned versus poorly-managed pasture). Treatments to provide a range of soil pH values (aluminum, nil, calcium) were applied to ascertain their effect on various growth response traits of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), white clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), big flower vetch (Vicia grandiflora Scop.), and flatpea (Lathyrus sylvestris L.). Averaging over all soils and treatments, shoot production increased in the order-alfalfa < red clover, white clover, trefoil, flatpea < vetch, while root production increased in the order-alfalfa < red clover, white clover < trefoil, vetch < flatpea. Main effects for soil source were significant (p less than or equal to 0.05) for shoot N uptake for red clover, trefoil and flatpea only, but not for root production for any of the species with the exception of alfalfa. Alfalfa shoot and root production, and N uptake, were significantly (p less than or equal to 0.05) reduced by low-level (1.5 cmol.kg-1 soil) Al treatment compared to the untreated (nil) soils, whereas the same traits for white clover were significantly (P less than or equal to 0.05) increased. These traits were generally unaffected by Al treatment for red clover, trefoi1, vetch and flatpea. Low-level (1.5 Mg.ha-1) Ca amendment also had generally little effect on any of the response traits for any of the species examined. Shoot N uptake appeared to be the most sensitive plant response trait to the resulting subtle soil chemical changes. These results indicate that all of the perennial legumes examined, with the exception of alfalfa, were able to establish and obtain acceptable production levels in acidic (approximately pH 5.2) ultisols w1th at least some history of pasture management.