Up to 75% of nitrogen (N) taken up during cauliflowers production is allocated to leaves, which are left as crop residues after harvest. The inclusion of cauliflower, cultivated alone or intercropped with legumes, in rotation schemes, is a promising tool to optimize N availability to subsequent crops. This original study assessed, for the first time in South Tyrol, Italy, the effect of removal or soil incorporation of cauliflower and clover residues on the growth and N uptake of subsequent lettuce. In 2015, cauliflower was sole-cropped or intercropped with clover, under different N regimes (N0, N1, N2, N3 = 0, 75, 150, 300 kg N ha⁻¹). Cauliflower and clover residues were either removed or incorporated in the soil in 2016. The effects of the residual fertility left by the N fertilizer, the two cropping systems, and the crop residues were assessed on the yield and N uptake of two subsequent lettuce crops. Isotopic ¹⁵N-labeled cauliflower residues were additionally used to quantify the N contribution of cauliflower residues to lettuce growth. During the first lettuce crop, residues incorporation was the only factor increasing lettuce yields (+41%) and N uptake (+58%). The residual effect of N1 and N2 rates increased the lettuce N uptake when clover residues were incorporated. During the second lettuce crop, residues incorporation increased lettuce yields (+26%) and N uptake (+44%). On average, 64% and 35% of the lettuce N amounts, in the first and second cycles, respectively, derived from cauliflower residues, and accounted for 38% of the total N contained in cauliflower residues (214 kg N ha⁻¹). Results from this experiment, uncommon for the examined species, demonstrate that incorporation of cauliflower and clover residues provides an excellent source of N for lettuce. Incorporating residues of the preceding cauliflower crop, alone or intercropped with clover, before establishing the lettuce crop, substantially reduce the N fertilization needs of subsequent lettuce crops.

花椰菜生产过程中吸收的高达 75% 的氮 (N) 分配给叶子，这些叶子在收获后作为作物残留物留下。在轮作计划中加入单独种植或与豆科​​植物间作的花椰菜是优化后续作物氮利用率的有前景的工具。这项最初的研究首次在意大利南蒂罗尔评估了去除或土壤掺入花椰菜和三叶草残留物对随后生菜的生长和氮吸收的影响。2015 年，花椰菜单作或与三叶草间作，在不同的施氮量（N0、N1、N2、N3 = 0、75、150、300 kg N ha ^-1）。2016 年，花椰菜和三叶草的残留物被去除或掺入土壤中。评估了氮肥、两种种植系统和作物残留物对随后两种莴苣作物的产量和氮吸收量的影响。同位素¹⁵N 标记的花椰菜残留物还用于量化花椰菜残留物对生菜生长的 N 贡献。在第一次生菜作物期间，残留物掺入是提高生菜产量（+41%）和氮吸收（+58%）的唯一因素。当加入三叶草残留物时，N1 和 N2 比率的残留效应增加了生菜的 N 吸收。在第二季生菜作物中，残留物的掺入提高了生菜产量（+26%）和氮吸收（+44%）。在第一个和第二个循环中，平均 64% 和 35% 的生菜氮含量分别来自花椰菜残渣，占花椰菜残渣中总氮含量的 38% (214 kg N ha ^-1）。该实验的结果在所检查的物种中并不常见，它表明花椰菜和三叶草残留物的掺入为生菜提供了极好的 N 来源。在建立莴苣作物之前，将先前的花椰菜作物的残留物单独或与三叶草间作，大大减少了随后的莴苣作物的氮肥需求。