Use of olive mill waste mix as peat surrogate in substrate for strawberry soilless cultivation

The aim of paper was to evaluate the suitability of olive mill waste mixture (OMWM) as growth media for strawberry soilless cultivation. OMWM was used at the rate of 0, 25, 50, 75% (v/v) as peat substitute. In order to assess nutrient supply to plants by OMWM, the experimental design included fertigated (standard) and unfertigated sets. Some of the chemical and physical parameters of the growth media were analysed at the beginning and end of cultivation, while plant nutrient uptake was assessed by means of petiole- and leaf blade-tissue analyses for the main macro- (N, K, Ca, Mg, Na) and micro- (Fe, Mn, Zn, Cu) elements. Quantitative and qualitative assessments of yield were also made. Plants grown on OMWM amended substrate showed an initial slight phytotoxicity particularly at higher rate (75%) probably as a consequence of the high values of electrical conductivity recorded in the OMWM water extract. Successive water leaching caused by irrigation or fertigation reduced EC towards values compatible to strawberry cultivation. Yield data and tissues analyses showed that OMWM performed adequately as a substitute for peat and satisfied the plant nutrient needs in the fertigated trial. However, it appeared that nitrogen provided by OMWM was insufficient in achieving adequate yield in the unfertigated trial. The use of OMWM showed high compatibility in soilless strawberry cultivation being an effective and cheap alternative to peat; therefore, a realistic cost reduction for growers was evident. The relatively high amount of nutrients found in the growth media at the end of strawberry cultivation meant that it can be recycled in agriculture as soil amendment.