Neocleous Damianos, Savvas Dimitrios, Giannothanasis Evangelos, Ntatsi Georgia
Laboratory of Plant Nutrition, Department of Natural Resources and Environment, Agricultural Research Institute, Nicosia, Cyprus.
Laboratory of Vegetable Production, Department of Crop Science, Agricultural University of Athens, Athens, Greece.
Front Plant Sci. 2024 Jul 23;15:1411572. doi: 10.3389/fpls.2024.1411572. eCollection 2024.
The management of nitrogen (N) fertilization is of fundamental importance in hydroponics. To reduce the supply of nitrate (NO ) in fertigation recipes for Batavia lettuce crops grown in closed hydroponics, partial replacement of nitrate by chloride (NO /Cl) at different ratios but with the same equivalent sum was experimentally tested. The experiment included four nutritional treatments in the replenishment nutrient solution, particularly T1; 0.7 mM Cl/19 mM NO , T2; 2 mM Cl/17.7 mM NO , T3; 4 mM Cl/15.7 mM NO and T4; 6 mM Cl/13.7 mM NO . The results showed that reducing nitrate supply combined with equivalent increase in chloride application gradually reduced the gap between nitrate input and nitrogen uptake concentrations, with the smallest differences occurring in T4 treatment, which reduced the nitrate concentration in the drainage by 50%. The tested treatments led to very small variations in plant water uptake, production of fresh biomass and nutritional quality, which is justified by the proper functioning of key physiological mechanisms, such as stomatal conductance, which was followed by an increased efficiency of nitrogen use up to 25% (kg fresh biomass kg N supply). The steady level of C/N ratio in the plant tissue irrespective of NO /Cl supply ratio points to sufficiency in photosynthetic products and adequacy in the supply of nitrogen, although leaf Cl content increased up to 19.6 mg g dry weight in the lowest NO /Cl treatment. Nutrient uptake concentrations were determined as follows: 13.4 (N), 1.72 (P), 10.2 (K), 3.13 (Ca), 0.86 (Mg, mmol L), 27.8 (Fe), 5.63 (Mn), 5.45 (Zn) and 0.72 (Cu, μmol L). This study suggests that replacing 30% of NO supply with Cl in fertigation recipes for hydroponic lettuce crops reduces leaf nitrate content without affecting physiological processes, growth, and quality, verifying in parallel the role of chloride as a beneficial macronutrient. Finally, a relationship between Cl uptake and its concentration in the root zone solution was established enabling the simulation of chloride to water consumption.
在水培中，氮肥管理至关重要。为减少封闭式水培中种植的巴达维亚生菜作物施肥配方中硝酸盐（NO₃⁻）的供应，通过实验测试了以不同比例但等量总和的氯化物（Cl⁻）部分替代硝酸盐（NO₃⁻/Cl⁻）的情况。该实验在补充营养液中包括四种营养处理，具体为T1；0.7 mM Cl⁻/19 mM NO₃⁻，T2；2 mM Cl⁻/17.7 mM NO₃⁻，T3；4 mM Cl⁻/15.7 mM NO₃⁻和T4；6 mM Cl⁻/13.7 mM NO₃⁻。结果表明，减少硝酸盐供应并同时等量增加氯化物施用量逐渐缩小了硝酸盐输入与氮吸收浓度之间的差距，T4处理中的差异最小，该处理使排水中的硝酸盐浓度降低了50%。所测试的处理导致植物水分吸收、新鲜生物量生产和营养品质的变化非常小，这可通过关键生理机制（如气孔导度）的正常运作来解释，随后氮利用效率提高了25%（每千克新鲜生物量每千克氮供应）。无论NO₃⁻/Cl⁻供应比例如何，植物组织中C/N比的稳定水平表明光合产物充足且氮供应充足，尽管在最低NO₃⁻/Cl⁻处理中叶片Cl含量增加至19.6 mg g干重。营养吸收浓度测定如下：13.4（N）、1.72（P）、10.2（K）、3.13（Ca）、0.86（Mg，mmol L）、27.8（Fe）、5.63（Mn）、5.45（Zn）和0.72（Cu，μmol L）。本研究表明，在水培生菜作物的施肥配方中用Cl⁻替代30%的NO₃⁻供应可降低叶片硝酸盐含量，而不影响生理过程、生长和品质，同时验证了氯化物作为有益大量元素的作用。最后，建立了Cl⁻吸收与其在根区溶液中浓度之间的关系，从而能够模拟氯化物对水分消耗的影响。
