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

Authors: YANG, TENG - The Ohio State University; Altland, James; SAMARAKOON, UTTARA - The Ohio State University

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2021
Publication Date: 8/22/2021
Citation: Yang, T., Altland, J.E., Samarakoon, U. 2021. Evaluation of organic substrates as an alternative to perlite for cucumber production in the Dutch bucket hydroponic system. Acta Horticulturae. 1317:319-326. https://doi.org/10.17660/actahortic.2021.1317.37.
DOI: https://doi.org/10.17660/actahortic.2021.1317.37

Interpretive Summary: The Dutch bucket system is one of the most commonly used soilless culture systems in the US. Dutch buckets are ideal for larger and vine crops, such as tomatoes (Solanum lycopersicum), cucumbers (Cucumis sativus), peppers (Capsicum annuum), eggplants (Solanum melongena) and others. Early adopters of the system were successful using perlite and thus all subsequent local recommendations were based on its use. Perlite has very low water holding capacity, so irrigation water is retained superficially and released directly. As a result, Dutch bucket systems typically release large quantities of nutrient-laden effluents that must be captured and recycled or lost to the surrounding environment. In the US, many small growers lack the equipment and expertise to capture and recycle the effluent. An ideal substrate would be locally available and sustainable, economically affordable, and with desirable physical and chemical properties such as low bulk density, high aeration and with adequate water holding capacity during crop production. The objective of this study was to evaluate the performance of five regional and sustainable organic substrates or mixtures with peat or pine bark as an alternative to perlite in the Dutch bucket system for cucumber production. Our preliminary investigation provided evidence that replacing perlite with medium-texture pine bark for cucumber grown in Dutch bucket system could reduce cost and leaching nutrients without affecting reproductive growth at the early fruit stage.

Technical Abstract: he 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 cv. 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% to 17% and 26% to 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.