Simulating NaCl accumulation in a closed hydroponic crop of zucchini: Impact on macronutrient uptake,growth, yield,and photosynthesis
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| Abstract: | Zucchini squash (Cucurbita pepo L.) plants were grown in a closed‐loop hydroponic system and supplied with nutrient solution (NS) containing NaCl at different concentrations (0.7, 3, 5, and 7 mM). The primary aim of the study was to define the relationship between the concentration of Na+ and Cl? in the root zone solution and the respective Na+/water or Cl?/water uptake ratios (uptake concentrations, UC). A second objective was to determine the UC of macronutrients (i.e ., N, P, K, Ca, and Mg) and to test whether they are influenced by the gradual increase of the root zone salinity due to progressive NaCl accumulation. Two experiments were conducted, of which one (spring crop) was used to parameterize an existing empirical model, while the second one (autumn‐winter crop) was commissioned to test the validity of the determined model parameters. Both Cl? and Na+ ions accumulated progressively in the root zone solution over time, showing a tendency to stabilize at final concentrations according to the corresponding NaCl treatment. The relationship between the Na+ and Cl? concentrations in the root zone and the Na+/water or Cl?/water uptake ratios was exponential and the model parameters successfully fitted to data from crops cultivated in different growth seasons. This model may be used to monitor Na+ and Cl? concentrations in the root environment of zucchini crops as relationships of the plant water consumption. The exposure of plants to NaCl affected the UC of N, K, Ca, and Mg, but the results for some nutrients were not consistent in both growth seasons. The measurements of plant growth characteristics (i.e ., biomass, yield, fruit quality, and photosynthesis) revealed that water resources containing up to 3 mM NaCl do not cause unacceptable yield losses in zucchini crops grown in completely closed hydroponic systems. |
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| Keywords: | Cucurbita pepo squash salinity nutrient solution recycling uptake concentration |
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