The researchers of Iowa State University's objectives were to quantify the growth and tissue mineral nutrient concentrations of cilantro, dill, and parsley in response to nutrient solution electrical conductivity (EC) under low and high photosynthetic daily light integrals (DLI).
Three-week-old seedlings of cilantro, dill, and parsley were transplanted into nutrient-film technique hydroponic systems with one of five nutrient solution EC treatments (0.5, 1.0, 2.0, 3.0, or 4.0 dS·m−1) in greenhouses under a low (~7.0 mol·m−2·d−1) or high (~18.0 mol·m−2·d−1) DLI. The DLI, but not nutrient solution EC, affected culinary herb growth.
For example, fresh mass increased by 21.0 (154%), 17.1 (241%), or 13.3 g (120%) for cilantro, dill, and parsley, respectively, for plants grown under high DLI compared to those grown under a low DLI; dry mass followed a similar trend. Tissue nutrient concentrations were generally affected by either DLI or EC. For those nutrients affected by DLI, concentrations increased with increasing DLI, except for potassium (K; all species) and manganese (Mn; dill).
For those nutrients affected by EC, Ca and Mg decreased with increasing EC, while the remaining increased with increasing EC. When our tissue nutrient data are compared to recommended tissue concentrations, the vast majority of elements were either within or above recommended tissue ranges for cilantro, dill, and parsley. Our results demonstrate cilantro, dill, and parsley can be successfully grown across a range of EC, regardless of the light intensity of the growing environment.
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