Performance of cucumber (Cucumus sativus L.) and sweet pepper (Capsicum annuum L.) in various local growing media, as alternative for rockwool in 
Saudi Arabia

W. Voogt, A. Alharbi, M. Almuwalid, S. Alsahly, J.B. Campen, H. van der Heide, M.E. Abdelaziz, M. Osman, I. Tsafaras, M. Qaryouti, F. de Zwart
Soilless culture is considered the best system for growing crops to overcome problems of soil-borne diseases and for achieving sustainable goals for saving water and nutrients. However, in many countries, the commonly used growing media, are expensive or even unavailable. To address for suitable sustainable local alternatives for the commonly used growing media, a research project was conducted at the Estidamah Research Centre at Riyadh in Saudi Arabia, studying the potential of two local substrates (volcanic rock and date palm wastes). Date palm waste (DPW) is a renewable source, locally available in large quantities since date production is a major industry in Saudi Arabia and volcanic rock (VR) is a widely available, natural, reusable and very cost-effective material. Different types of DPW were used, and pre-treated in several ways (sieved, flushed, sterilized), while VR was used from one source. Both media were compared with standard rockwool (RW) and perlite (PL) with cucumber and sweet pepper. The trials focused on the applicability water- and nutrient conditions and the crop performance in growing cycles of several months. DPW and VR were tested with the crops grown in a climate-controlled Venlo-type greenhouse with Pad-Fan cooling. The results and experiences of the first experiment were used to improve the DPW and VR treatments for the next trial. The first trial (cucumber) showed dramatic results for VR and a low score with DPW. For the next crop (sweet pepper), the fertigation strategy and design of VR substrate system were modified as well as improvements of the selection of DPW raw material and pre-treatment applications were applied. These modifications seriously improved the results, with virtually no differences for VR compared to the reference grown in RW or PL. In this respect, it could be concluded that, both VR and DPW, under conditions of right treatment, are suitable for use as local materials in soilless culture under Saudi Arabian conditions.
Voogt, W., Alharbi, A., Almuwalid, M., Alsahly, S., Campen, J.B., van der Heide, H., Abdelaziz, M.E., Osman, M., Tsafaras, I., Qaryouti, M. and de Zwart, F. (2021). Performance of cucumber (Cucumus sativus L.) and sweet pepper (Capsicum annuum L.) in various local growing media, as alternative for rockwool in 
Saudi Arabia. Acta Hortic. 1317, 287-294
DOI: 10.17660/ActaHortic.2021.1317.33
date palm waste, perlite, volcanic rock, soilless culture, substrate

Acta Horticulturae