Although humic acid has been demonstrated to improve the yield of some crops, the long‐term effects of continuous cropping on peanut (Arachis hypogaea L.) remain largely undetermined. In the present study, we aimed to compare the continuous effects of different concentrations of humic acid on the continuously cropped peanut. A 3‐yr experiment was conducted in the North China Plain. Treatments of 50 kg ha⁻¹ (T1), 100 kg ha⁻¹ (T2), and 150 kg ha⁻¹ (T3) humic acid were applied with inorganic fertilizer along with the equal N, P, and K inputs. Compared with the control group, humic acid increased the yield and oxidative stress tolerance of continuously cropped peanut. To elucidate the mechanism, various physiological indicators were evaluated and compared in this study. First, humic acid increased chlorophyll content and the ability to incorporate nutrients, and the maximum effect was achieved by T3 in 2016. Second, the activities of nitrate reductase and sucrose phosphate synthase in peanut leaves were significantly increased after humic acid treatment, and the most increase was achieved by T2. Third, the activities of antioxidant enzymes were increased, the malondialdehyde (MDA) content was reduced in 2016–2018 by T3, and the same effects were observed in roots and leaves. Fourth, the content of the hormone was changed after humic acid treatment. Collectively, humic acid improved the yield and tolerance of continuously cropped peanut due to the above‐mentioned four reasons, which were conducive to alleviating the obstacles of continuously cropped peanut.

中文翻译：

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腐殖酸对连作土壤中花生生长的生理效应

尽管已证明腐殖酸可以提高某些农作物的产量，但连作对花生（Arachis hypogaea L.）的长期影响仍未确定。在本研究中，我们旨在比较不同浓度的腐殖酸对连续播种花生的持续影响。在华北平原进行了为期3年的实验。处理50 kg ha ^-1（T1），100 kg ha ^-1（T2）和150 kg ha ^-1将（T3）腐殖酸与相同量的N，P和K一起与无机肥料一起施用。与对照组相比，腐殖酸提高了连作花生的产量和抗氧化胁迫能力。为了阐明其机理，本研究对各种生理指标进行了评估和比较。首先，腐殖酸增加了叶绿素含量和吸收养分的能力，在2016年的T3达到了最大的效果。其次，腐殖酸处理后花生叶片中硝酸还原酶和蔗糖磷酸合酶的活性显着增加，其中T2实现了增长。第三，T3在2016–2018年增加了抗氧化酶的活性，降低了丙二醛（MDA）含量，在根和叶中也观察到了相同的效果。第四，腐殖酸处理后激素含量发生变化。归因于上述四个原因，腐殖酸共同提高了连作花生的产量和耐受性，有利于减轻连作花生的障碍。