Evaluation of substrates for cucumber production in the Dutch bucket hydroponic system.

• Peat, medium grade pine bark, coarse grade pine bark, coir, and wood fiber in general had more nutrient retention and less nutrient drainage than perlite. • Organic substrates showed a similar or better growth rate in comparison to perlite with respect to vegetative and reproductive growth. • Cucumber yield is equal to or greater than perlite when grown with organic substrates. • Pine bark improved essential phytochemicals in fruits of cucumber. The Dutch bucket system is commonly used for production of high-wire crops such as tomatoes, peppers, and cucumbers in controlled environment agriculture. It is a hydroponic system that utilizes containers typically filled with perlite as the substrate. Perlite provides good aeration however has higher leachate in the systems. Furthermore, demand for regional and sustainable substrates is increasing. Our preliminary study showed growth parameters in vegetative and early fruiting stages of cucumber grown with five regionally accessible substrates are comparable to perlite. Thus, the current study evaluated the performance of five organic substrates in comparison to perlite in the Dutch bucket system for the full production cycle of cucumber (Cucumis sativus 'Picolino F1'). The substrates evaluated were sphagnum peat, medium grade pine bark (Bark-M), coarse grade pine bark (Bark-C), coir, and wood fiber. Leachate rates in Bark-M, coir, and peat were lower than perlite by 18.0%, 24.0%, and 38.1%, respectively. Plant leaf area indicated better vegetative growth of cucumber with wood fiber, but pine bark had higher yield and fruit quality than perlite. Bark-M resulted in greater yield and fruit vitamin C content, which were 23.9% and 48.3% higher than perlite, respectively. On the other hand, although Bark-C had a similar yield to perlite, its fruit mineral nutrient content including nitrogen (except wood fiber), phosphorus, potassium, calcium (except Bark-M and wood fiber), sulfur (except Bark-M and wood fiber), iron (except Bark-M), zinc, boron, copper (except wood fiber), and manganese (except Bark-M), as well as total anthocyanin and total phenols were highest among all substrates. In summary, organic substrates investigated could provide equal or higher cucumber yields and quality than perlite in the Dutch bucket hydroponic system. [ABSTRACT FROM AUTHOR]