Physiological effects of humic acid in peanut growing in continuous cropping soil

Abstract

AbstractAlthough 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.