Evaluation of organic substrates as an alternative to perlite for cucumber production in the Dutch bucket hydroponic system

The Dutch bucket hydroponic system is commonly used for production of high-wire crops such as tomatoes, peppers and cucumbers in controlled environment agriculture. It utilizes containers, typically filled with perlite as the substrate. However, perlite is a non-renewable material that can be difficult to dispose after use. Thus, the current study evaluated the performance of five regional and sustainable organic substrates as an alternative to perlite in the Dutch bucket system. The model crop used was cucumber (Cucumis sativus 'Picolino F₁') due to its fast growth rate. The substrates evaluated were sphagnum peat (Peat), medium-texture pine bark (PB-M), coarse pine bark (PB-C), blended (coarse and medium) pine bark (PB-Blend), and a 50% sphagnum peat: 50% blended pine bark substrate (Peat+PB-Blend). Plants were grown for four weeks in the Dutch bucket system till early fruiting. Peat had the greatest water holding capacity, followed by the Peat+PB-Blend and PB-M. Perlite, PB-C, and PB-Blend had the least water holding capacity. Throughout the study, electrical conductivity (EC) and pH of leachate from perlite were higher than all other substrates, while pH from Peat was lower than all other substrates. Although cucumber grown in Peat had greater vegetative growth (plant height and early-season shoot dry weight) than perlite, there was no significant difference in reproductive growth (flower time, fruit number, and fruit dry yield). Cucumber grown in PB-M had earlier first flower time and higher early-season flower number than other substrates by 6-17% and 26-55%, respectively, which suggested higher yields. Future research will evaluate similar substrates with an emphasis on physical properties and irrigation management with more comprehensive analysis of plant yield and fruit quality.