Recently, a cold wave has affected China from west to east and from north to south, causing frost damage to flowering rapeseed, regreening wheat, field vegetables, fruit trees, and other crops. Numerous studies and applications have shown that functional products such as humic acid, humic acid fertilizers, and fulvic acid fertilizers can increase the content of free proline, soluble sugars, and soluble proteins in plants under low temperature stress, enhance the activity of antioxidant enzymes, and improve the cold resistance of crops. The research results on the application of humic acid series agricultural products in cold resistance in 15 crops are summarized below for everyone to share.
Anhui Agricultural University, Cheng Fujiu, et al., studied the physiological effects of humic acid on seed germination, nitrogen absorption, and cold resistance of rapeseed. The results showed that soaking with humic acid (FA) could effectively activate the activities of protease, peptidase, and acid phosphatase during rapeseed seed germination, increase seed germination index and vigor index, enhance nitrate reductase activity in seedlings, and promote nitrogen absorption. Under low-temperature stress, humic acid could enhance the activities of superoxide dismutase (SOD) and catalase (CAT) in rapeseed seedlings and increase ascorbic acid content, suppressing malondialdehyde (MDA) production, reducing cell electrolyte leakage, alleviating chlorophyll damage, maintaining cell physiological functions, increasing photosynthetic rate and root vigor, and significantly reducing respiration rate. [Source: Journal of Anhui Agricultural University, 1995, 22(2):123-128]
Zhu Xialing et al. from the Crop Institute of the Chinese Academy of Agricultural Sciences studied the effects of the transpiration inhibitor fulvic acid (FA) on the cold resistance physiology of winter wheat. The results showed that wheat leaves sprayed with FA had a relative membrane permeability 8.30 percentage points lower than the control, and the free proline content in the leaves increased by 17.55% compared to the control. The soluble sugar content in both the wheat leaves and tillering nodes was higher than the control. [Source: Beijing Agricultural Science, 1995(4):20-21]
Jin Ping from the Soil and Fertilizer Institute of Heilongjiang Academy of Agricultural Sciences studied the effects of humic acid on the cold resistance of rice. The results showed that under low-temperature stress, 300, 400, 600 mg/L humic acid could increase the proline content in rice by 3.0-28.8 μg/g·FW, increase the polyphenol oxidase activity by 0.08-0.34 mg·g·min, increase the abscisic acid content by 44.983-0.179 f·mol/g·FW, reduce rice membrane permeability by 1.86%-0.36%, decrease malondialdehyde content by 6.45-7.96 μmol/L·g·FW. The experiment confirmed that humic acid can indeed improve the cold resistance of rice. [Source: Journal of Northeast Agricultural University, 1997, 28(1):90-93]
