Suitability of a New Application Method for Controlled-release Fertilizers in Long-term Forcing Culture of Tomato by Using Capillary Wick Irrigation System

Abstract

We investigated the suitability of a newly developed controlled-release fertilizer (CRF) fertilization method known as tank-fertilization (TF) to simplify fertilization and to reutilize the substrate in long-term forcing culture of tomato by using a root-proof capillary wick irrigation system. We compared three CRF fertilization methods: (1) TF; (2) mixed with the substrate completely (MF); and (3) packed in bags and placed on the wick (PF). These were also compared to fertilization with a liquid fertilizer (LF). Marketable fruit yield was similar among MF, TF, and LF, but lower in PF. Both shoot and fruit dry weights were lower in PF than in MF and TF. Lower dry weight in PF was probably attributable to the lower nutrient uptake caused by the lower elusion rate of fertilizers. For each element, nutrient uptake per plant and nutrient utilization efficiency for fruit production was higher with LF than with MF and TF. Nutrient residue of nitrogen, phosphorous and potassium in the substrates in TF was lower than those in MF, indicating that the TF method can prevent nutrient enrichment of the substrates and that the substrates treated by this method have high reusability. Thus, the technique of "tank-fertilization (TF)" of CRFs is possible and very practical in the long-term forcing culture of tomatoes by using the root-proof capillary wick irrigation system.