Evaluation of Alternative Substrates under Varying Fertigation Methods for Highwire Cucumber Propagation

Choosing the right substrate plays a critical role in propagation success. An ideal substrate should support high germination and vigorous root and shoot development, while also minimizing environmental impacts. Organic substrates such as wood fiber, coir, and pine bark are being explored as alternatives to conventional substrates such as mineral wool, perlite, and peat, which have well-documented environmental and disposal challenges in highwire vegetable production. However, their performance during propagation under different fertigation strategies remains unclear. We evaluated the interaction of three organic substrates—wood fiber and coir mix (WF-coir), pine bark < 0.32 cm (fine bark), and peat—along with two electrical conductivity (EC) levels (1.1 and 2.2 mS·cm –1 ) and three irrigation methods (overhead, subirrigation, and a combination of both) for cucumber ( Cucumis sativus L.) propagation across three sequential greenhouse experiments. In Expt. 1, WF-coir and fine bark were compared with mineral wool under overhead irrigation with supplemental subirrigation. Expt. 2 included peat in addition to the substrates used in Expt. 1 and tested the impact of concentration of nutrient solution (EC levels) under overhead irrigation with drainage trays. Expt. 3 evaluated substrates under overhead irrigation only. WF-coir performed comparably to mineral wool in most growth parameters, but exceeded it in shoot fresh weight and leaf area (Expt. 1). Fine bark supported greater seedling height than peat, whereas peat showed the greatest soil plant analysis development value among all substrates (Expt. 2). In Expt. 3, WF-coir, fine bark, and mineral wool produced taller seedlings under a greater EC, whereas peat maintained a consistent height across EC levels. Overall, WF-coir demonstrated a potential for a lower impact alternative to mineral wool and peat under high-nutrient, overhead irrigation conditions. Fine bark may require amendments to enhance water and nutrient retention.