Soilless plant culture is any method of growing plants without the use of soil as a rooting medium known as a substrate or growing medium
(Savvas et al., 2013). Compared with soil based cultivation, soilless production can be more cost effective
(Grafiadellis et al., 2000; Sindhu et al., 2010), producing higher yields and prompter harvests from smaller areas of land (Raviv and Lieth, 2008;
Khalaj et al., 2011; Nejad and Ismaili, 2014). Soilless systems also have generally higher water and nutrient use efficiencies (Van Os, 1999). As a result, they have become increasingly important globally over the last 50 years (Schmilewski, 2009).
Effective soilless growing medium must have a physical structure that creates an appropriate balance of air and water for healthy root development. This balance must be maintained over an entire crop production cycle, which can last from several weeks to more than a year. Growing medium structure is determined by the size, shape, texture and physical arrangement of the particles from which it is composed
(Bilderback et al., 2005). Chemical properties as pH, electrical conductivity, cation exchange capacity and nutrient availability have been measured across a diverse range of growing media and are extensively reviewed (Lemaire, 1995; Argo, 1998; Silber, 2008;
Murumkar et al., 2013). Biological properties are also an important consideration for organic materials, as they can have large impacts on growing medium performance (Carlile and Wilson, 1991; Alsanius and Wohanka, 2009).
Nowadays, a wide range of soilless culture techniques have been developed and commercially introduced for intensive production of horticultural crops, particularly vegetables under greenhouses condition. Replacing soil with other growing medium for growing vegetable crops especially cucumber, pepper, tomatoes
etc. resulting in better control of plant nutrition and eliminate of plant diseases that caused by soil (Olympios, 1995;
Kurup et al., 2011). It helps to avoid problems related to monoculture of plants in the same land for years
(Fecondini et al., 2011). Furthermore, it would address the problems related to proliferation of soil borne pathogen in the soil cultivation.
Two types of waste are generated from the process of olive oil extraction; one is a solid residue called olive pomace (or Jift as locally named) and a liquid waste which is olive mill wastewater or Zibar as named locally in Palestine. Olive pomace retains a small amount of olive oil and consists mainly of water, olive skin, olive flesh, fragments of pulp and pieces of kernels. Olive pomace chemical composition is generally characterized by a high content of crude fiber and sugars (mainly polysaccharides) and moderate values of crude protein, fatty acids (oleic acid), polyalcohols, polyphenols and other pigments which may affect plant growth and development
(Saviozzi et al., 2001; Muik et al., 2004; Brunetti et al., 2005). However, the chemical composition of olive pomace may vary widely in relation to the agronomic and technological conditions of production.
In Palestine, the only treatment that is done to the wastes of olive mills is the partial reuse of the overall produced olive pomace for the soap factories. The olive pomace is collected and then extracted by hydrocarbons to extract the remaining oil to be used for producing soap. The remaining olive pomace is dried and used as burning material to produce energy for the extraction process in the soap factories. The olive pomace is also used partly for combustion to heat houses during the winter season. In addition to using olive pomace for space heating and soap industry there are other reported potential uses of olive pomace such as fertilizer compost
(Haddadin et al., 2009), animal fodder (Haddadin and Abdulrahim, 1999), source for the manufacture of activated carbon
(Mameri et al., 2000), source of bio-pesticides
(Cayuela et al., 2008), co-firing with coal in power stations (Cliffe and Patumsawad, 2001). The improper disposal of olive pomace causes a serious environmental issue in Palestine because of its negative effects on soil and ground water (Tawarah and Rababah, 2013).
The objective of this study was to investigate the potential of using olive pomace as growing medium for horticulture crop cultivation and its behavior on growth performance of eggplant and cucumber production as case study inside greenhouse.
