The reduction in peat usage is an important issue in U. K. horticulture, a major destination for growing media produced in the Republic of Ireland. This study examined the possibility of using composted seafood waste (CSW) in a traditional peat based medium and in a peat reduced medium containing composted green waste (CGW). The growth and development of tomato test plants (Lycopersicon lycopersicum var. Shirley), grown in peat based and peat/CGW media with reduced fertiliser rate (50%) amended with three levels of CSW added at rates of 0, 5 and 10% (v/v), was assessed. The objective was to examine if composted seafood waste could compensate for the reduced fertilizer level in these growing media. The plant growth parameters examined were plant height, plant spread, fresh shoot weight and percentage dry matter. Overall performance improved with the addition of CSW. The addition of CSW at 10% to the reduced fertilized peat medium and a 5% addition of CSW to the reduced fertilized Peat/CGW medium produced the most favourable results. Plants in these treatments were not significantly different from each other and only had one significant difference from their controls in terms of % dry matter. The addition of CSW at 5% to the peat media also produced favourable results. The addition of CSW at 10% to the peat/CGW medium produced poor plants. It is concluded that the addition of CSW at an appropriate rate can produce tomato plants of acceptable quality. However, the immobilisation of phosphorus by CSW could result in restrictions to plant growth and development.
