effect of particle size distribution of perlite and its mixture with organic substrates on cucumber in hydroponics system

the selection of a growing medium is one of the most important decisions in the culture of hydroponic crops. in order to select a suitable medium for hydroponic cucumber (cucumis sativus l. cv. negin), an experiment was carried out on growing media containing different particle sizes of perlite and organic substrates in a run-to-waste system in a greenhouse experiment. the growing media tested were: very course perlite (vc-p, 70% by volume in the range of 2-3 mm), course perlite (c-p, 70% by volume in the range of 1-2 mm), medium perlite (m-p, 70% by volume in the range of 1 mm), fine perlite (f-p, 70% by volume in the range of 0.5-1 mm), very fine perlite (vf-p, 70% by volume < 0.5 mm), sawdust (sd) (100%), one mixture of vc-p and sd (50:50, v/v), one mixture of vc-p and poplar chip (ch) (50:50, v/v) and one mixture of vc-p and wheat straw (st) (50:50, v/v). the eight treatments were arranged in a randomized complete block design with four replications. the results showed that there were significantly differences in the mean fruit weight, plant height, and leaf area of cucumber with respect to media containing very course (vc)-grade perlite (horticulture-grade perlite) and its incorporation with organic substrates, and media containing different grades of perlite (from very course to very fine-grade perlite). the incorporation of wheat straw (50:50) into vc-grade perlite brought decreases of about 35% in the mean fruit weight of cucumber, respectively. media containing fine grade-perlite led to a significant increase in mean fruit weight (50%), plant height (25%), and leaf area (70%) of cucumber as compared with media consisting of very course-grade perlite. it was concluded that the medium containing fine-grade perlite had the best performance for cucumber plant growth.