Comparison of cucumbers grown in rockwool or perlite at two leaching fractions

Abstract

Cucumbers (Cucumis sativus L. 'Vetomil') were grown in rockwool or perlite to evaluate these media for efficient hydroponic cucumber production under Florida greenhouse conditions. Plants were grown using a double-stem training method, and the frequency of irrigations was controlled by a weighing lysimeter for each treatment. In Expt. 1, plants were grown in rockwool with 29% or 17% leaching fraction (LF) and in perlite with a 17% LF. Nitrogen, P, and K concentrations in the complete nutrient solution were 175, 50, and 180 mg·L-1, respectively. In Expt. 2, N, P, and K concentrations were increased to 225, 60, and 225 mg·L-1, respectively. Other nutrient concentrations and LFs remained as in Expt. 1. In Expt. 1. yields (fruit count and total fruit mass) were higher from plants grown in rockwool at 29% LF than from plants grown in rockwool or perlite at 17% LF. However, in Expt. 2, when nutrient concentrations were higher, total fruit mass was greater from plants grown at the lower LF, although there was no difference in fruit number. In both experiments, cucumber yield did not differ when grown at the same LF in either rockwool or perlite. Electrical conductivity (EC) and pH of the nutrient solution from the growing bags were not affected when LFs were decreased. In Expt. 1, the pH and EC ranged from 6.1 to 7.0 and from 0.9 to 1.6 mS·cm-1, respectively, across all treatments. In Expt. 2, pH and EC ranged from S.3 to 6.9 and from 0.6 to 2.5 mS·cm-1, respectively, across all treatments.