Regression analyses were used to survey the effects of extractable NO3‐N, P, K, Ca, Mg, and soil pH on electrical conductivity (EC) in a 1: 1: 1 (v/v/v) peat‐sand‐perlite azalea (Rhododendron sp.) growing medium amended with soluble 21–3–6 (N‐P‐K) or slow‐release 18–3–6 fertilizer sources. Simple linear correlations indicated a high degree of relationship between NO3‐N, P, and K versus EC (r=0.95**, 0.79**, and 0.79**, respectively). Partial regression coefficients suggested that NO.‐N was the primary ionic species affecting EC. The correlations between EC versus P and K were apparently related to their intercorrelation with NO3‐N, associated with the use of N‐P‐K fertilizers. These relationships were constant across fertilizer sources. The results demonstrate a potential for the use of soil EC in the estimation of NO3‐N in soilless rooting media.