An Analysis of Yield and Nitrate Concentration in Hydroponic vs. Field Grown Cucumbers
Of all of the essential nutrients, nitrogen (N) is the most limiting for plant growth. Most plants need nitrogen in large amounts as an essential component of proteins, nucleic acids and other cellular constituents. However excessive use of nitrogen fertilizers has led to the accumulation of nitrate (NO3) in some vegetable products, causing great harm to human health. To study this, an experiment was carried out in east of Tehran, Iran. Hydroponic and field grown cucumbers were compared in regards to their nitrate concentration to see which had the least amount of nitrate accumulation in its fruit. The effect this element had on overall yield was also studied. A completely randomized block design was used with 8 treatments and 3 replications. The treatments included: T1: control, T2: KNO3, T3: ZnSO4, T4: MgSO4, T5: CaNO3, T6: CaCl2, T7 HNO3, T8 mixture of all 7 treatments together. 12 cucumber plants were used for each treatment. After one month of applying the treatments, samples were taken to the lab for analysis of their nitrate concentrations. Results showed the mean nitrate concentration for hydroponic cucumbers equaled 42.6 mg/kg FW, while for conventional or field cucumbers this was 208.2 mg/kg FW. Overall hydroponic cucumbers had a lower nitrate concentration, and showed a much better quality. HNO3, CaNO3, KNO3, and the mixed treatment had the highest nitrate concentration of all in their fruit while they showed no significant difference with the control treatment in regards to yield. On the other hand, ZnSO4 gave the highest yield of all, and overtime lowered the nitrate content of the fruit. It appears hydroponic cultures allow for a more balanced use of fertilizers, providing plants with exactly what they need and therefore improving the quality and yield of products.
Keywords: Nitrate, Cucumber, Hydroponics
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