Perennial forage legume growth in acidic soils from the major series of the Appalachian Hill‐Lands

Abstract

The lack of highly effective forage legume symbioses is thought to be a major constraint to the renovation of acidic soils of the Appalachian region for pasture use. A growth chamber experiment was initiated with 14 fresh soils, each of a different series, from diverse sites within the region to determine the need for rhizobial inoculation, and the soil chemical properties limiting growth, of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), white clover (Trifolium repens L.), and birdsfoot trefoil (Lotus corniculatus L.). Effective, naturalized populations of rhizobia producing acceptable (>50% maximum) shoot growth were found in few of the soils. Commercial rhizobial mixtures were effective in producing similarly acceptable growth in three soils for alfalfa and red clover, but only in one soil for white clover and birdsfoot trefoil. Soil rankings based on asymbiotic shoot growth were similar for all species, particularly when only the better soils were considered, and changed little (r = 0.71∗) compared to symbio‐ tically‐grown plants. Soil chemical properties typically limiting growth of all species, particularly alfalfa, were low pH, and low Ca and high Al concentrations. Birdsfoot trefoil was least sensitive to these soil acidity‐related factors. For plant species and soil combinations that allowed only ineffective symbioses, no significant correlation was found between differences in asymbiotic and symbiotic shoot growth and any chemical properties of the seven soils involved. Overall, these results demonstrate the need for improved rhizobia for many of for a number of these soils, and the difficulty of this task as a result of the multitude of interactions of soil, plant, and bacterial properties that determine rhizobium effectiveness.

Notes

Present address: USDA, ARS, NRI, ECL, B‐001, Room 221, BARC‐W, 10300 Baltimore Avenue, Beltsville, MD 20705–2350.