Efficient utilization of fertilizer P and K by a crop depends, to a large extent, on the amount of roots that contact the fertilizer nutrient, as well as the capacity of the root to absorb the contacted nutrient. In order to find a Nigerian cowpea that utilizes soil and applied nutrients best, five cowpea cultivars commonly cultivated in Nigeria were grown in fertile and N, P, and K deficient soils in the greenhouse. Specific objectives were to determine differences in root growth (length) and nutrient uptake efficiencies of roots (μg/m) among the five cultivars. To determine the effect of age on the ability of a cowpea plant to utilize soil nutrients, cowpea cultivar ‘H113–4’ was grown for 30 days in solution culture and changes in root length and nutrient uptake rates (μg/m‐day) as functions of plant age were evaluated. When grown in fertile soil, ‘Ife‐brown’, H113–4, and Westbred cultivars had significantly greater root lengths (17.5, 17.2, and 16.7 m respectively) than ‘1534’ (14.3 m.); while ‘Crimson's’ root length (15.4 m) was intermediate. In the N‐P‐K‐ deficient soil, however, Crimson had the most extensive root system (19 m). Apparently, H113–4 had the greatest total uptake of P, K, and Ca (9.9 mg), K uptake efficiency (360 μg K/m root length), and shoot:root ratio (W/W). Also, the P and Ca uptake efficiencies of this cultivar (160 and 75 μg/m respectively), and the dry matter yield (0.94 g) were among the highest. The total length of roots of Hl13–4 was a linear function of plant age (R2 = 0.94) up to 30 days of age. Phosphorus and K uptake rates in solution culture decreased tremendously from 34 μgP/m‐day and 380 μgK/m‐day, at 5 days old, to 8 μgP/m‐day and 95 μgK/m‐day at 30 days, respectively. Deficiency of K in the solution culture markedly reduced P uptake by the root. It is concluded that H1 13ߝ4 variety has superior potential over other cowpea varieties studied for efficient utilization of applied P and K; and that the nutrient absorption capacity of young cowpea roots decreases rapidly with age.