PDF(Pubmed)
Abstract：
The management of nitrogen (N) fertilization is of fundamental importance in hydroponics. To reduce the supply of nitrate (NO3 -) in fertigation recipes for Batavia lettuce crops grown in closed hydroponics, partial replacement of nitrate by chloride (NO3 -/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 NO3 -, T2; 2 mM Cl-/17.7 mM NO3 -, T3; 4 mM Cl-/15.7 mM NO3 - and T4; 6 mM Cl-/13.7 mM NO3 -. 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-1 N supply). The steady level of C/N ratio in the plant tissue irrespective of NO3 -/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-1 dry weight in the lowest NO3 -/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-1), 27.8 (Fe), 5.63 (Mn), 5.45 (Zn) and 0.72 (Cu, μmol L-1). This study suggests that replacing 30% of NO3 - 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.
摘要：
氮（N）施肥的管理在水培法中至关重要。为了减少在封闭水培法中种植的巴达维亚生菜作物的灌溉施肥配方中硝酸盐（NO3-）的供应，实验测试了用不同比例但当量和相同的氯化物（NO3-/Cl-）部分替代硝酸盐。实验包括补充营养液中的四种营养处理，特别是T1；0.7mMCl-/19mMNO3-，T2；2mMCl-/17.7mMNO3-，T3;4mMCl-/15.7mMNO3-和T4;6mMCl-/13.7mMNO3-。结果表明，减少硝酸盐的供应加上氯化物的等效增加逐渐减少了硝酸盐输入和氮吸收浓度之间的差距，T4治疗的差异最小，使排水中的硝酸盐浓度降低了50%。测试的处理导致植物水分吸收的变化非常小，生产新鲜生物质和营养质量，关键生理机制的正常运作是合理的，如气孔导度，其次，氮的利用效率提高了25％（kg新鲜生物质kg-1N供应）。无论NO3-/Cl-供应比如何，植物组织中C/N比的稳定水平都表明光合产物充足，氮供应充足，尽管在最低的NO3-/Cl-处理下，叶片Cl-含量增加至19.6mgg-1干重。养分吸收浓度测定如下：13.4(N)，1.72(P),10.2(K),3.13(Ca),0.86(Mg,mmolL-1)，27.8(Fe),5.63(Mn),5.45（Zn）和0.72（Cu，μmolL-1)。这项研究表明，在水培莴苣作物的施肥配方中，用Cl-代替30％的NO3-供应可降低叶片硝酸盐含量，而不会影响生理过程。增长,和质量，平行验证氯化物作为有益的常量营养素的作用。最后,建立了Cl-吸收与其在根区溶液中的浓度之间的关系，从而可以模拟氯化物对水的消耗。
