Vegetable production requires improved nitrogen (N) management practices. Monitoring petiole sap nitrate concentration ([NO₃⁻–N]) is a simple and cheap method to evaluate crop N status. The sensitivity of petiole sap [NO₃⁻–N] to assess crop N status of sweet pepper was evaluated. Three sweet pepper crops were grown in different cropping seasons, each with an autumn-winter growing period. The crops commenced in 2014, 2016, and 2017. Combined fertigation and drip irrigation frequently applied (every 1–4 days) complete nutrient solution throughout each crop. The crops were grown in a greenhouse in soil. Five N treatments as N concentrations were applied throughout each crop: N1 (2.0–2.4 mmol L⁻¹); N2 (5.3–6.2 mmol L⁻¹); N3 (9.7–12.6 mmol L⁻¹); N4 (13.1–16.1 mmol L⁻¹); N5 (16.7–20.0 mmol L⁻¹). These corresponded to very deficient, deficient, conventional, excessive and very excessive N supply. Petiole sap [NO₃⁻–N] was determined every 1–2 weeks and related to Nitrogen Nutrition Index (NNI), which was used as an indicator of crop N status. For each of the N treatments in each crop, petiole sap [NO₃⁻–N] was relatively constant throughout the crop. The relationship between petiole sap [NO₃⁻–N] and NNI, for pooled data from the three pepper crops, was described by (a) the polynomial equation $\text{NNI}=-1.10\mathrm{E}-07\times {\mathit{Sap}}^{\mathit{2}}+0.000473\times \mathit{Sap}+0.5514$ with an R² of 0.84, and (b) the segmented linear equations $\text{NNI}=0.00034\times \mathit{Sap}+0.572$ and NNI = 1.04, with an R² of 0.83. Sufficiency values for maximum growth of sweet pepper were obtained by (a) solving the polynomial equation for NNI = 1.0, and (b) using the intercept value of the horizontal line of the segmented linear regression. The corresponding sufficiency values for the duration of a complete crop cycle were 1441 and 1367 mg NO₃⁻–N L⁻¹, respectively. A sufficiency value of 1400 mg NO₃⁻–N L⁻¹ was rounded-off and suggested for the duration of a complete crop cycle of greenhouse-grown sweet pepper in SE Spain. The relationships between petiole sap [NO₃⁻–N] and NNI, and the derived sufficiency values for the flowering and early fruit growth, and harvest phenological stages were similar to those determined for the entire crop. Petiole sap [NO₃⁻–N] is a sensitive and effective method to monitor crop N status of sweet pepper.

蔬菜生产需要改善氮素管理实践。监测叶柄汁液中硝酸盐的浓度（[NO ₃ ^-– N]）是评估作物氮素状况的一种简单而廉价的方法。评估了叶柄汁液[NO ₃ ^-– N]对甜椒作物氮素状况的敏感性。在不同的种植季节种植了三种甜椒作物，每种作物都有秋冬季的生长期。作物分别于2014年，2016年和2017年开始。施肥和滴灌相结合的方法（每1-4天）通常应用在每种作物上，完全营养。作物生长在土壤温室中。五个N处理如N浓度在每种作物施加：N1（2.0-2.4毫摩尔大号^{- 1}）; 氮气（5.3–6.2 mmol L^{− 1}）; N3（9.7-12.6毫摩尔大号^{- 1}）; N4（13.1–16.1 mmol L ^{− 1}）；N5（16.7–20.0 mmol L ^{− 1}）。这些对应于非常不足，不足，常规，过量和非常过量的氮供应。每1-2周测定一次叶柄汁液[NO ₃ ^-- N]，并与氮素营养指数（NNI）相关，后者被用作作物氮素状况的指标。对于每种作物的N种处理中的每一种，叶柄汁液[NO ₃ ^-- N]在整个作物中相对恒定。对于来自三种辣椒作物的汇总数据，叶柄汁液[NO ₃ ^-– N]与NNI之间的关系由（a）多项式方程式描述$\text{国民净收入}=-1.10\mathrm{E}-07\times {\mathit{树液}}^{\mathit{2个}}+0.000473\times \mathit{树液}+0.5514$R ²为0.84，以及（b）分段线性方程$\text{国民净收入}=0.00034\times \mathit{树液}+0.572$NNI = 1.04，R ²为0.83。通过（a）求解NNI = 1.0的多项式方程，以及（b）使用分段线性回归的水平线的截距值，可获得甜椒最大生长的充足值。在整个作物周期内，相应的充足值分别为1441和1367 mg NO ₃ ^-- NL ^{- 1}。四舍五入为1400 mg NO ₃ ^-- NL ^{- 1}的充足值，并建议用于西班牙东南部温室种植甜椒的整个作物周期。NO叶柄SAP之间的关系[ ₃ ^-–N]和NNI，以及开花和果实早期生长以及收获物候期的衍生充足值与为整个作物确定的相似。叶柄汁液[NO ₃ ^-– N]是监测甜椒作物氮素状况的灵敏有效方法。