Abstract
The use of incinerated ash from sewage sludge as an alternative substrate for soilless culture was investigated.
Incinerated ash was combined with charcoal powder to increase porosity and ceramic glaze to permit a lower incineration temperature, and the mixture was incinerated and used as an alternative substrate. The physical properties of the substrate were greatly influenced by the ratio of mixed materials; however, we aimed to develop a suitable product that could not only be used for soilless culture but that could be easily returned to the soil without becoming industrial waste. The optimal compounding ratio of materials was found to be 10: 1: 3 (incinerated ash from sewage sludge: ceramic glaze: charcoal powder) when burned at 850 °C. The average moisture content of samples was about 60 %, and the average hardness (compression load) was about 40 N. These physical properties are sufficient to endure the handling requirements of this product for plant culture. Tomatoes grown in soilless culture had identical growth rates and fruiting ratios when grown on rockwool and the incinerated ash mixture; however, the latter substrate resulted in tomatoes weighing 1.5 times that of tomatoes grown hydroponically on rockwool. At the end of culture, the physical properties of the substrates were examined. The moisture content of the incinerated ash mixture was 70 % and the average hardness was about 40 N, values sufficient to warrant re-use of the substrate for additional soilless culture.
