Establishment, growth, and persistence of forage legumes on shallow, infertile, and acidic hill-land pasture soils, often because of the expense of optimal liming and fertilization, remains a problem. A better understanding of the mechanism of inhibition of symbiosis establishment in these soils, and its alleviation by minimal liming, could aid in the solution of this problem. White clover (Trifolium repens L.) seedlings were planted in two model systems (deepots or plates), utilizing an air-dried, nonsterile Ultisol limed from pHw 4.71 (nil lime) to 4.99, and inoculated with effective rhizobia (Rhizobium leguminosarum bv. trifolii). Both model systems demonstrated the stimulatory effect of low-level liming (soil pH increase) on nodulation 14 days after planting (DAP) and before differences in shoot mass responses were apparent. Examination of roots grown in soil plates (∼1/5 volume of deepots) at 3, 6, 8, 10, 12 and 14 DAP revealed a significant (r = 0.90;P ≤ 0.05) nodulation response to soil pH, but only at 14 DAP. However, the consistent pattern of nodulation responses to soil pH, almost throughout the entire growth period, suggests that nodulation was being stimulated by low-level liming as early as 6 to 8 DAP. With the exception of small differences toward the end of the experiment (12–14 DAP), root development (total length, diameter, volume, surface area, tip, and fork number) was unaffected by soil pH. Root length, sorted into eight diameter classes, was similarly unresponsive to soil pH. Collectively, these results suggest that inhibition of symbiosis establishment in our soil plate model system occurs at the cellular (root hair and/or nodule primordium) level, rather than at the tissue (root) level. From a practical (field) perspective, our finding that the rhizobial level interacted with soil pH on nodulation intensity suggests that the development of either a more acidic soil-tolerant plant cultivar or rhizobial strain would lead to a more rapid and robust symbiosis in infertile, acidic soils.