High levels of oxygen consumptions were recorded with cooled RZTs as compared to that of control-non-cooled RZT for all cropping periods in both the years. Significant (p < 0.05) differences between the treatments were observed in oxygen consumption by the roots of cucumber in the cropping periods in both the years. The results showed that cooling of nutrient solution temperature influenced positively the levels of DO in the fresh nutrient solution feeding tank and drain nutrient solution for all cropping periods in both the years.
All the treatments received the same nutrient concentrations. The plants were grown in pots filled with perlite medium in randomized complete design (RCD) with four replications. T1 (22 ᵒC), T2 (25 ᵒC) and T3 (28 ᵒC) through cooling nutrient solution besides non-cooled treatment T4 (33 ᵒC) as control. Three cooling treatments were applied viz. summer (June-August), fall (September-November) and spring (February-May) in two consecutive years 018.
The plants were cultivated in recirculating hydroponic system in a greenhouse with dimensions of 9 m wide × 30 m long and total area of 270 m2 during three cropping periods in Oman viz. In this respect, the present investigation was undertaken to comprehend the influence of nutrient solution temperature on its oxygen level (ambient dissolved oxygen in feeding tank), growth, yield and quality of cucumber (Cucumis sativus L.) plants. This suggests that easier and economical control of root-zone temperature (RZT) could be an effective solution to the temperature stress for the crop plants in hydroponics. High nutrient solution temperature stress around root-zone (rhizosphere) is a major factor limiting hydroponic crop growth due to change in dissolved oxygen (DO) levels in nutrient solution during the high-temperature seasons.
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