LAUSR

BACKGROUND Chars are emerging materials as constituents of growth media. However, chars of different origin differ in their characteristics and more studies are needed to ratify them for such a role. The characteristics of coir mixed with 0%, 10%, 25%, 50%, 75%, and 100% (v/v) of two biochars, from forest waste (BCH-FW) and from olive mill waste (BCH-OMW), and one hydrochar, from forest waste (HYD-FW), and their effects on growth, yield and fruit quality of two tomato cultivars (Gransol RZ and Cuarenteno) were assessed. RESULTS Chars negatively affected plant growth and yield but not fruit quality. The effect was related to the char dose and was larger in HYD-FW and BCH-FW than in BCH-OMW, despite the high salinity of the latter, and more acute in Cuarenteno than in Gransol RZ. The results were discussed on the basis of the large particle size of BCH-FW, which could have caused low nutrient solution retention and, hence, reduced plant nutrient uptake, and the high water-holding capacity, poor aeration and large CO2 emission of HYD-FW, which could lead to root anoxia. CONCLUSION BCH-OMW can be used at high proportion in media for tomato cultivation. The use of BCH-FW at a high proportion might be taken into consideration after adjusting particle size, yet this needs additional assays. HYD-FW is inadequate for soilless containerized tomato cultivation. © 2017 Society of Chemical Industry.