Effects of Substrate Materials Mixed with Sands on Substrate Properties and Tomato Fruit Production in Sandponics

Abstract

The effects of substrate materials mixed with sand on the physicochemical properties, fruit quality and yield of tomato plants were investigated to improve tomato production by sandponic cultivation system. Zeolite-mixed substrate lost moisture more easily and contained more Na than sand substrate. EC and NO₃-N content in this substrate remained low during the cultivation period. In the zeolite-mixed substrate, plant growth was restricted, resulting in a low yield and the production of fruits with high Brix values. Addition of activated carbon to sand restricted the early growth of plants and deteriorated fruit quality, while it increased fruit weight. The addition of soil to sand improved fruit quality without any detrimental effects on yield. The addition of coconut coir improved the physicochemical properties of substrates (e.g., gravity and water retentivity), stimulating early growth of plants and early yield. The results suggested that the potential usefulness of coconut coir as a conditioner of sand substrate should be further studied under different irrigation schedules.