Fig. 2. Total ¹⁵N recovery expressed as a percentage of added ¹⁵N in plant, growth media, and those that were unaccounted for. Error bars are standard errors of the means (n = 4). The same lowercase letters in the same N pool indicate statistically nonsignificant differences (P > 0.05). Compost age significantly (P < 0.05) affected ¹⁵N recovery in growth media and total recovery but not in plant (P = 0.056). Treatment codes indicate different ages (1, 2, 3, and 4 yr old) of compost without N addition (1YN0, 2YN0, 3YN0, and 4YN0, respectively) or with N addition (1YN1, 2YN1, 3YN1, and 4YN1, respectively), and soil represents the soil-based growth media.