The imbalance between nitrate/ammonium (NO₃⁻/NH₄⁺) ratio in the nutrient solution induces ammonia toxicity that can be attenuated by phosphorus (P). However, there are no reports of the beneficial effect of P in mitigating ammonia toxicity for citrus. The aim of this study was to evaluate the response of orange seedlings to nitrogen (N) in different NO₃⁻/NH₄⁺ ratios in the nutrient solution and whether P attenuates ammonia toxicity. Thus, two experiments were conducted in a greenhouse. Experiment I consisted of five NO₃⁻/NH₄⁺ ratios, and experiment II of three concentrations of P supply combined with two NO₃⁻/NH₄⁺ ratios. About 120 days after the beginning of the treatment applications, biological and nutritional evaluations were carried out in both experiments. The best NO₃⁻/NH₄⁺ ratio was 80/20 for promoting the greater development of orange seedlings Pêra-rio (Citrus sinensis L.) grafted on lemon tree (Citrus limonia L.). On the other hand a NH₄N:NO₃N ratio of 26:74 induces severe ammonia toxicity in the plant. Increasing the concentration of P supply in the nutrient solution (10.0 mmol L⁻¹) is an important new strategy to mitigate ammoniacal toxicity in these plants because it reduced the leakage of electrolytes and increased the production of photosynthetic pigments, the photosynthetic rate, the dry matter production and the seedling quality.

（NO硝酸盐/铵之间的不平衡₃ ^- / NH ₄ ⁺）的营养液诱导氨的毒性比可通过磷（P）被衰减。但是，尚无关于减轻磷对柑橘的氨毒性的有益作用的报道。本研究的目的是评价橙色幼苗对氮（N）在不同NO响应₃ ^- / NH _4分⁺中的营养液，以及是否P衰减氨毒性比。因此，在温室中进行了两个实验。实验I由五个NO ₃ ^- / NH ₄ ⁺比，和实验II三个浓度供磷的具有两个NO组合₃ ^- / NH ₄ ⁺的比率。在开始治疗应用后约120天，在两个实验中均进行了生物学和营养评估。最好NO ₃ ^- / NH ₄ ⁺之比为80/20促进橙苗Pêra的-RIO（的更大发展甜橙接枝柠檬树（L.）柑桔limonia L.）。另一方面，NH ₄ N：NO ₃ N比率为26:74会在植物中引起严重的氨中毒。增加营养液中磷的供应浓度（10.0 mmol L^-1）是减轻这些植物氨氮毒性的重要新策略，因为它减少了电解质的泄漏并增加了光合色素的产量，光合速率，干物质产量和幼苗质量。