Abstract Intensive vegetable production in soil is often associated with large N losses to the environment. To contribute to improved N management of sweet pepper, this work developed a critical nitrogen curve (CNC). It also developed N recommendations and examined N use efficiency (NUE) and potential NO3− leaching loss in relation to increasing total available nitrogen (TAN). TAN is the sum of the soil mineral N at planting, N mineralized from soil organic material, and mineral N fertilizer. Three sweet pepper crops were grown in soil with autumn-winter cropping cycles in greenhouse conditions. Five different N concentrations in the nutrient solution were applied throughout the crop cycle: very N deficient (N1), N deficient (N2), conventional N management (N3), excessive N (N4) and very excessive N (N5). A critical N curve of % N c = 4.71 × D M P - 0.22 was determined for sweet pepper. Relative yield of the three crops had a strong linear-plateau relationship (R2 = 0.66) with integrated nitrogen nutrition index (NNIi). Maximum yield was associated with an NNIi of 0.86. In the three crops, total yield, dry matter production (DMP) and crop N uptake were generally strongly related to increasing TAN. An optimal TAN value (minimum TAN for maximum yield) of 425 kg N ha−1 was determined using a linear-plateau regression model. N uptake efficiency (NuptE) decreased exponentially with increasing TAN, from almost 0.90 kg kg−1 in the N1 treatment to 0.30 kg kg−1 in the N5 treatment. The sum of residual mineral N and leached NO3−–N was considered to be potential NO3− leaching loss. Potential NO3− leaching loss increased exponentially, with increasing TAN, to 686–1034 kg N ha−1 in the highest N treatments. For the optimal TAN value, NuptE was 0.63 kg kg−1 and the potential NO3− leaching was 125 kg N ha−1. The CNC and derived NNI values provide valuable information for N management of pepper. Consideration of TAN as the crop N supply enables maximum yield with less fertilizer N and less risk of N loss.

中文翻译：

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温室生产中的甜椒和氮供应：临界氮曲线、农艺反应和氮流失风险

摘要 土壤中的集约化蔬菜生产通常与大量的氮向环境损失有关。为了有助于改进甜椒的氮管理，这项工作开发了一个临界氮曲线 (CNC)。它还制定了 N 建议并检查了 N 使用效率 (NUE) 和与增加总可用氮 (TAN) 相关的潜在 NO3− 浸出损失。TAN 是种植时土壤矿物氮、土壤有机物质矿化的氮和矿物氮肥的总和。三种甜椒作物在温室条件下以秋冬季作物周期在土壤中种植。在整个作物周期中，营养液中施用了五种不同浓度的氮：非常缺氮 (N1)、缺氮 (N2)、常规氮管理 (N3)、过量氮 (N4) 和非常过量氮 (N5)。% N c = 4 的临界 N 曲线。71 × DMP - 0.22 被确定为甜椒。三种作物的相对产量与综合氮营养指数（NNIi）具有很强的线性平台关系（R2 = 0.66）。最大产量与 0.86 的 NNIi 相关。在这三种作物中，总产量、干物质产量 (DMP) 和作物吸氮量通常与 TAN 的增加密切相关。使用线性平台回归模型确定了 425 kg N ha-1 的最佳 TAN 值（最大产量的最小 TAN）。N 吸收效率 (NuptE) 随着 TAN 的增加呈指数下降，从 N1 处理中的几乎 0.90 kg kg-1 到 N5 处理中的 0.30 kg kg-1。残留矿物 N 和浸出的 NO3−–N 的总和被认为是潜在的 NO3− 浸出损失。随着 TAN 的增加，潜在的 NO3− 浸出损失呈指数增加，在最高 N 处理中增加到 686–1034 kg N ha-1。对于最佳 TAN 值，NuptE 为 0.63 kg kg−1，潜在的 NO3− 浸出量为 125 kg N ha−1。CNC 和派生的 NNI 值为辣椒的 N 管理提供了有价值的信息。考虑将 TAN 作为作物 N 供应量，可在减少施氮量和减少 N 损失风险的情况下获得最大产量。